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Электронный компонент: OPA2674

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FEATURES
D
WIDEBAND +12V OPERATION: 220MHz (G = +4)
D
UNITY-GAIN STABLE: 250MHz (G = +1)
D
HIGH OUTPUT CURRENT: 500mA
D
OUTPUT VOLTAGE SWING: 10V
PP
D
HIGH SLEW RATE: 2000V/
s
D
LOW SUPPLY CURRENT: 18mA
D
FLEXIBLE POWER CONTROL: SO-14 Only
D
OUTPUT CURRENT LIMIT (
800mA)
APPLICATIONS
D
POWER LINE MODEM
D
xDSL LINE DRIVERS
D
CABLE MODEM DRIVERS
D
MATCHED I/Q CHANNEL AMPLIFIERS
D
BROADBAND VIDEO LINE DRIVERS
D
ARB LINE DRIVERS
D
HIGH CAP LOAD DRIVER
OPA2674 RELATED PRODUCTS
SINGLES
DUALS
TRIPLES
NOTES
OPA691
OPA2691
OPA3691
Single +12V Capable
THS6042
15V Capable
OPA2677
Single +12V Capable
DESCRIPTION
The OPA2674 provides the high output current and low
distortion required in emerging xDSL and Power Line
Modem driver applications. Operating on a single +12V
supply, the OPA2674 consumes a low 9mA/ch quiescent
current to deliver a very high 500mA output current. This
output current supports even the most demanding ADSL
CPE requirements with > 380mA minimum output current
(+25
C minimum value) with low harmonic distortion.
Differential driver applications deliver < -85dBc distortion
at the peak upstream power levels of full rate ADSL. The
high 200MHz bandwidth also supports the most
demanding VDSL line driver requirements.
Power control features are included in the SO-14 package
version to allow system power to be minimized. Two logic
control lines allow four quiescent power settings. These
include full power, power cutback for short loops, idle state
for no signal transmission but line match maintenance,
and shutdown for power off with a high impedance output.
Specified on
6V supplies (to support +12V operation), the
OPA2674 will also support a single +5V or dual
5V
supply. Video applications will benefit from a very high
output current to drive up to 10 parallel video loads (15
)
with < 0.1%/0.1
dG/dP nonlinearity.
Single-Supply CPE Upstream Driver
82.5
2k
2k
1
F
17.4
100
2V
PP
AFE
Output
324
20
324
1 /2
O P A 26 74
1 /2
O P A 26 74
+12V
1:1.7
15V
PP
Twisted Pair
17.7V
PP
20
17.4
+6.0V
OPA2674
SBOS270 - AUGUST 2003
Dual Wideband, High Output Current
Operational Amplifier with Current Limit
www.ti.com
Copyright
2003, Texas Instruments Incorporated
Please be aware that an important notice concerning availability, standard warranty, and use in critical applications of Texas Instruments
semiconductor products and disclaimers thereto appears at the end of this data sheet.
All trademarks are the property of their respective owners.
PRODUCTION DATA information is current as of publication date. Products
conform to specifications per the terms of Texas Instruments standard warranty.
Production processing does not necessarily include testing of all parameters.
OPA2674
SBOS270 - AUGUST 2003
www.ti.com
2
ORDERING INFORMATION
PRODUCT
PACKAGE-LEAD
PACKAGE
DESIGNATOR(1)
SPECIFIED
TEMPERATURE
RANGE
PACKAGE
MARKING
ORDERING
NUMBER
TRANSPORT
MEDIA, QUANTITY
OPA2674
SO-8
D
-40
C to +85
C
OPA2674ID
OPA2674ID
Rails, 100
OPA2674IDR
Tape and Reel, 2500
OPA2674
SO-14
D
-40
C to +85
C
OPA2674I-14D
OPA2674I
-
14D
Rails, 58
OPA2674I-14DR
Tape and Reel, 2500
(1) For the most current specification and package information, refer to our web site at www.ti.com.
ABSOLUTE MAXIMUM RATINGS
(1)
Power Supply
6.5VDC
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Internal Power Dissipation
See Thermal Analysis
. . . . . . . . . . . . . .
Differential Input Voltage
1.2V
. . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Input Common-Mode Voltage Range
VS
. . . . . . . . . . . . . . . . . . . .
Storage Temperature Range: D,
-
14D
-40
C to +125
C
. . . . . . . . . . .
Lead Temperature (soldering, 10s)
+300
C
. . . . . . . . . . . . . . . . . . . . .
Junction Temperature (TJ)
+150
C
. . . . . . . . . . . . . . . . . . . . . . . . . . .
ESD Rating
Human Body Model (HBM)(2)
2000V
. . . . . . . . . . . . . . . . . . . . . .
Charge Device Model (CDM)
1000V
. . . . . . . . . . . . . . . . . . . . . .
Machine Model (MM)
100V
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
(1) Stresses above these ratings may cause permanent damage.
Exposure to absolute maximum conditions for extended periods
may degrade device reliability. These are stress ratings only, and
functional operation of the device at these or any other conditions
beyond those specified is not supported.
(2) Pins 2 and 6 on SO-8 package, and pins 1 and 7 on SO-14
package > 500V HBM.
This integrated circuit can be damaged by ESD. Texas
Instruments recommends that all integrated circuits be
handled with appropriate precautions. Failure to observe
proper handling and installation procedures can cause damage.
ESD damage can range from subtle performance degradation to
complete device failure. Precision integrated circuits may be more
susceptible to damage because very small parametric changes could
cause the device not to meet its published specifications.
PIN CONFIGURATIONS
Top View
SO-8
Top View
SO-14
NC = No Connection
1
2
3
4
8
7
6
5
+V
S
Out B
-
In B
+In B
OPA2674ID
Out A
-
In A
+In A
-
V
S
1
2
3
4
5
6
7
14
13
12
11
10
9
8
-
In A
+In A
A0
-
V
S
A1
+In B
-
In B
Out A
NC
NC
+V
S
NC
NC
Out B
Power
Control
OPA2674I-14D
OPA2674
SBOS270 - AUGUST 2003
www.ti.com
3
ELECTRICAL CHARACTERISTICS: V
S
=
6V
Boldface limits are tested at +25
C.
At T
A
= +25
C, A
1
= A
0
= 1 (full power: for SO
-
14 only), G = +4, R
F
= 402
, and R
L
= 100
, unless otherwise noted. See Figure 1 for AC performance only.
OPA2674ID, OPA2674I-14D
TYP
MIN/MAX OVER TEMPERATURE
TEST
PARAMETER
TEST CONDITIONS
+25
C
+25
C(1)
0
C to
+70
C(2)
-40
C to
+85
C(2)
UNITS
MIN/
MAX
TEST
LEVEL
(3)
AC Performance (see Figure 1)
Small-Signal Bandwidth (VO = 0.5VPP)
G = +1, RF = 511
250
MHz
typ
C
Small-Signal Bandwidth (VO = 0.5VPP)
G = +2, RF = 475
225
170
165
160
MHz
min
B
G = +4, RF = 402
220
170
165
160
MHz
min
B
G = +8, RF = 250
260
200
195
190
MHz
min
B
Peaking at a Gain of +1
G = +1, RF = 511
0.2
dB
typ
C
Bandwidth for 0.1dB Gain Flatness
G = +4, VO = 0.5VPP
100
40
35
30
MHz
min
B
Large-Signal Bandwidth
G = +4, VO = 5VPP
220
160
155
150
MHz
typ
C
Slew Rate
G = +4, 5V step
2000
1500
1450
1400
V/
s
min
B
Rise Time and Fall Time
G = +4, VO = 2V step
1.6
ns
typ
C
Harmonic Distortion
G = +4, f = 5MHz, VO = 2VPP
2nd-Harmonic
RL = 100
-72
-68
-67
-66
dBc
max
B
RL
500
-82
-80
-79
-78
dBc
max
B
3rd-Harmonic
RL = 100
-81
-79
-78
-77
dBc
max
B
RL
500
-93
-91
-90
-89
dBc
max
B
Input Voltage Noise
f > 1MHz
2
2.6
2.9
3.1
nV/
Hz
max
B
Noninverting Input Current Noise
f > 1MHz
16
20
21
22
pA/
Hz
max
B
Inverting Input Current Noise
f > 1MHz
24
29
30
31
pA/
Hz
max
B
NTSC Differential Gain
NTSC, G = +2, RL = 150
0.03
%
typ
C
NTSC Differential Gain
NTSC, G = +2, RL = 37.5
0.05
%
typ
C
NTCS Differential Phase
NTSC, G = +2, RL = 150
0.01
deg
typ
C
NTCS Differential Phase
NTSC, G = +2, RL = 37.5
0.04
deg
typ
C
Channel
-
to
-
Channel Crosstalk
f = 5MHz, Input Referred
-92
dB
typ
C
DC Performance(4)
Open
-
Loop Transimpedance Gain
VO = 0V, RL = 100
135
80
76
75
k
min
A
Input Offset Voltage
VCM = 0V
1
4.5
5
5.3
mV
max
A
Offset Voltage Drift
VCM = 0V
4
10
10
12
V/
C
max
B
Noninverting Input Bias Current
VCM = 0V
10
30
32
35
A
max
A
Noninverting Input Bias Current Drift
VCM = 0V
5
50
50
75
nA/
C
max
B
Inverting Input Bias Current
VCM = 0V
10
35
40
45
A
max
A
Inverting Input Bias Current Drift
VCM = 0V
10
100
100
150
nA/
C
max
B
Input(4)
Common
-
Mode Input Range (CMIR)(5)
4.5
4.1
4.0
4.0
V
min
A
Common
-
Mode Rejection Ratio (CMRR)
VCM = 0V, Input Referred
55
51
50
50
dB
min
A
Noninverting Input Impedance
250
2
k
pF
typ
C
Minimum Inverting Input Resistance
Open
-
Loop
22
12
min
B
Maximum Inverting Input Resistance
Open
-
Loop
22
35
max
B
Output(4)
Output Voltage Swing
No Load
5.1
4.9
4.8
4.7
V
min
A
Output Voltage Swing
RL = 100
5.0
4.8
4.7
4.5
V
min
A
RL = 25
4.8
V
typ
C
Current Output
VO = 0
500
380
350
320
mA
min
A
Short
-
Circuit Current
VO = 0
800
mA
typ
C
Closed-Loop Output Impedance
G = +4, f
100kHz
0.01
typ
C
Output(4) (SO-14 Only)
Current Output at Full Power
A1 = 1, A0 = 1, VO = 0
500
380
350
320
mA
min
A
Current Output at Power Cutback
A1 = 1, A0 = 0, VO = 0
450
350
320
300
mA
min
A
Current Output at Idle Power
A1 = 0, A0 = 1, VO = 0
100
60
55
50
mA
min
A
(1) Junction temperature = ambient for +25
C specifications.
(2) Junction temperature = ambient at low temperature limit; junction temperature = ambient +23
C at high temperature limit for over temperature
specifications.
(3) Test levels: (A) 100% tested at +25
C. Over temperature limits by characterization and simulation. (B) Limits set by characterization and
simulation. (C) Typical value only for information.
(4) Current is considered positive out of node. VCM is the input common-mode voltage.
(5) Tested < 3dB below minimum CMRR specification at
CMIR limits.
OPA2674
SBOS270 - AUGUST 2003
www.ti.com
4
ELECTRICAL CHARACTERISTICS: V
S
=
6V (continued)
Boldface limits are tested at +25
C.
At T
A
= +25
C, A
1
= A
0
= 1 (full power: for SO
-
14 only), G = +4, R
F
= 402
, and R
L
= 100
, unless otherwise noted. See Figure 1 for AC performance only.
TEST
LEVEL
(3)
OPA2674ID, OPA2674I-14D
TEST
LEVEL
(3)
MIN/MAX OVER TEMPERATURE
TYP
PARAMETER
TEST
LEVEL
(3)
MIN/
MAX
UNITS
-40
C to
+85
C(2)
0
C to
+70
C(2)
+25
C(1)
+25
C
TEST CONDITIONS
Power Supply
Specified Operating Voltage
6
V
typ
C
Maximum Operating Voltage
6.3
6.3
6.3
V
max
A
Maximum Quiescent Current
VS =
6V
18
18.6
18.8
19.2
mA
max
A
Minimum Quiescent Current
VS =
6V
18
17.4
16.5
16.0
mA
min
A
Power-Supply Rejection Ratio (PSRR)
f = 100kHz, Input Referred
56
51
49
48
dB
min
A
Power Supply (SO-14 Only)
Maximum Logic 0
A1, A0, +VS = +6V
2.5
2.0
1.8
1.5
V
max
A
Minimum Logic 1
A1, A0, +VS = +6V
3.3
3.6
4.0
4.2
V
min
A
Logic Input Current
A1 = 0V, A0 = 0V, Each Line
60
90
100
105
A
max
A
Supply Current at Full Power
A1 = 1, A0 = 1 (logic levels)
18.0
18.6
18.8
19.2
mA
max
A
Supply Current at Power Cutback
A1 = 1, A0 = 0 (logic levels)
13.3
14.2
14.4
14.8
mA
max
A
Supply Current at Idle Power
A1 = 0, A0 = 1 (logic levels)
4.0
4.8
5.1
5.3
mA
max
A
Supply Current at Shutdown
A1 = 0, A0 = 0 (logic levels)
1.0
1.3
1.4
1.5
mA
max
A
Output Impedance in Idle Power
G = +4, f < 1MHz
0.1
typ
C
Output Impedance in Shutdown
100
4
k
pF
typ
C
Supply Current Step Time
10% to 90% Change
200
ns
typ
C
Output Switching Glitch
Inputs at GND
20
mV
typ
C
Shutdown Isolation
G = +4, 1MHz, A1 = 0, A0 = 0
85
dB
typ
C
Thermal Characteristics
Specification: ID, I-14D
-40 to
+85
C
Thermal Resistance,
q
JA
ID SO
-
8
Junction
-
to
-
Ambient
125
C/W
typ
C
I-14D SO-14
100
C/W
typ
C
(1) Junction temperature = ambient for +25
C specifications.
(2) Junction temperature = ambient at low temperature limit; junction temperature = ambient +23
C at high temperature limit for over temperature
specifications.
(3) Test levels: (A) 100% tested at +25
C. Over temperature limits by characterization and simulation. (B) Limits set by characterization and
simulation. (C) Typical value only for information.
(4) Current is considered positive out of node. VCM is the input common-mode voltage.
(5) Tested < 3dB below minimum CMRR specification at
CMIR limits.
OPA2674
SBOS270 - AUGUST 2003
www.ti.com
5
ELECTRICAL CHARACTERISTICS: V
S
= +5V
Boldface limits are tested at +25
C.
At T
A
= +25
C, A
1
= 1, A
0
= 1 (Full Power: for SO-14 only), G = +4, R
F
= 453
, and R
L
= 100
, unless otherwise noted. See Figure 3 for AC
performance only.
OPA2674ID, OPA2674I-14D
TYP
MIN/MAX OVER TEMPERATURE
TEST
PARAMETER
TEST CONDITIONS
+25
C
+25
C(1)
0
C to
+70
C(2)
-40
C to
+85
C(2)
UNITS
MIN/
MAX
TEST
LEVEL
(3)
AC Performance (see Figure 3)
Small
-
Signal Bandwidth (VO = 0.5VPP)
G = +1, RF = 536
220
MHz
typ
C
Small
-
Signal Bandwidth (VO = 0.5VPP)
G = +2, RF = 511
175
140
130
120
MHz
min
B
G = +4, RF = 453
168
130
126
120
MHz
min
B
G = +8, RF = 332
175
140
130
125
MHz
min
B
Peaking at a Gain of +1
G = +1, RF = 511
0.6
dB
typ
C
Bandwidth for 0.1dB Gain Flatness
G = +4, VO = 0.5VPP
34
24
22
20
MHz
min
B
Large
-
Signal Bandwidth
G = +4, VO = 5VPP
190
140
135
130
MHz
typ
C
Slew Rate
G = +4, 2V Step
900
650
625
600
V/
s
min
B
Rise Time and Fall Time
G = +4, VO = 2V Step
2
ns
typ
C
Harmonic Distortion
G = +4, f = 5MHz, VO = 2VPP
2nd-Harmonic
RL = 100
-65
-63
-62
-61
dBc
max
B
RL
500
-72
-70
-69
-68
dBc
max
B
3rd-Harmonic
RL = 100
-72
-70
-69
-68
dBc
max
B
RL
500
-74
-71
-70
-69
dBc
max
B
Input Voltage Noise
f > 1MHz
2
2.6
2.9
3.1
nV/
Hz
max
B
Noninverting Input Current Noise
f > 1MHz
16
20
21
22
pA/
Hz
max
B
Inverting Input Current Noise
f > 1MHz
24
29
30
31
pA/
Hz
max
B
Channel
-
to
-
Channel Crosstalk
f = 5MHz, Input Referred
-92
dB
typ
C
DC Performance(4)
Open
-
Loop Transimpedance Gain
VO = 0V, RL = 100
110
72
70
68
k
min
A
Input Offset Voltage
VCM = 0V
0.8
3.5
4.0
4.3
mV
max
A
Offset Voltage Drift
VCM = 0V
4
10
10
12
V/
C
max
B
Noninverting Input Bias Current
VCM = 0V
10
30
32
35
A
max
A
Noninverting Input Bias Current Drift
VCM = 0V
5
50
50
75
nA/
C
max
B
Inverting Input Bias Current
VCM = 0V
10
35
40
45
A
max
A
Inverting Input Bias Current Drift
VCM = 0V
10
100
100
150
nA/
C
max
B
Input
Most Positive Input Voltage(5)
3.7
3.3
3.2
3.1
V
min
A
Most Negative Input Voltage(5)
1.3
1.7
1.8
1.9
V
min
A
Common
-
Mode Rejection Ratio (CMRR)
VCM = 2.5V, Input Referred
53
49
48
47
dB
min
A
Noninverting Input Impedance
250
2
k
pF
typ
C
Minimum Inverting Input Resistance
Open
-
Loop
25
15
min
B
Maximum Inverting Input Resistance
Open
-
Loop
25
40
max
B
Output
Most Positive Output Voltage
No Load
4.1
3.9
3.8
3.6
V
min
A
Most Positive Output Voltage
RL = 100
3.9
3.8
3.7
3.5
V
min
A
Most Negative Output Voltage
No Load
0.8
1.0
1.1
1.3
V
max
A
Most Negative Output Voltage
RL = 100
1.0
1.1
1.2
1.5
V
max
A
Current Output
VO = 0
260
200
180
160
mA
min
A
Closed
-
Loop Output Impedance
G = +4, f
100kHz
0.02
typ
C
Output (SO-14 Only)
Current Output at Full Power
A1 = 1, A0 = 1, VO = 0
260
200
180
160
mA
min
A
Current Output at Power Cutback
A1 = 1, A0 = 0, VO = 0
200
160
140
120
mA
min
A
Current Output at Idle Power
A1 = 0, A0 = 1, VO = 0
80
50
45
40
mA
min
A
(1) Junction temperature = ambient for +25
C specifications.
(2) Junction temperature = ambient at low temperature limit; junction temperature = ambient +23
C at high temperature limit for over temperature
specifications.
(3) Test levels: (A) 100% tested at +25
C. Over temperature limits by characterization and simulation. (B) Limits set by characterization and
simulation. (C) Typical value only for information.
(4) Current considered positive out of node. VCM is the input common-mode voltage.
(5) Tested < 3dB below minimum CMRR at min/max input ranges.
OPA2674
SBOS270 - AUGUST 2003
www.ti.com
6
ELECTRICAL CHARACTERISTICS: V
S
= +5V(continued)
Boldface limits are tested at +25
C.
At T
A
= +25
C, A
1
= 1, A
0
= 1 (Full Power: for SO-14 only), G = +4, R
F
= 453
, and R
L
= 100
, unless otherwise noted. See Figure 3 for AC
performance only.
TEST
LEVEL
(3)
OPA2674ID, OPA2674I-14D
TEST
LEVEL
(3)
MIN/MAX OVER TEMPERATURE
TYP
PARAMETER
TEST
LEVEL
(3)
MIN/
MAX
UNITS
-40
C to
+85
C(2)
0
C to
+70
C(2)
+25
C(1)
+25
C
TEST CONDITIONS
Power Supply (Single-Supply Mode)
Specified Operating Voltage
+5
V
typ
C
Maximum Operating Voltage
12.6
12.6
12.6
V
max
A
Maximum Quiescent Current
VS = +5V
13.6
14.8
15.2
15.6
mA
max
A
Minimum Quiescent Current
VS = +5V
13.6
12
11.7
11.4
mA
min
A
Power
-
Supply Rejection Ratio (PSRR)
f = 100kHz, Input Referred
52
dB
typ
C
Power Control (SO-14 Only)
Maximum Logic 0
A1, A0, +VS = +5V
1.5
1.0
0.9
0.8
V
max
A
Minimum Logic 1
A1, A0, +VS = +5V
2.4
2.7
3.1
3.3
V
min
A
Logic Input Current
A1 = 0V, A0 = 0V, Each Line
50
80
90
95
A
max
A
Supply Current at Full Power
A1 = 1, A0 = 1 (logic levels)
13.8
14.8
15.2
15.6
mA
max
A
Supply Current at Power Cutback
A1 = 1, A0 = 0 (logic levels)
10.2
10.8
11.1
11.4
mA
max
A
Supply Current at Idle Power
A1 = 1, A0 = 1 (logic levels)
3.0
3.2
3.5
3.8
mA
max
A
Supply Current at Shutdown
A1 = 0, A0 = 0 (logic levels)
0.6
0.9
1.0
1.1
mA
max
A
Output Impedance in Idle Power
G = +4, f = 1MHz
typ
C
Output Impedance in Shutdown
100
4
k
pF
typ
C
Supply Current Step Time
10% to 90% Change
200
ns
typ
C
Output Switching Glitch
Inputs at GND
20
mV
typ
C
Shutdown Isolation
G = +4, 1MHz, A1 = 0, A0 = 0
85
dB
typ
C
Thermal Characteristics
Specification: ID, I-14D
-40 to
+85
C
Thermal Resistance,
q
JA
ID SO
-
8
Junction
-
to
-
Ambient
125
C/W
typ
C
I-14D SO
-
14
100
C/W
typ
C
(1) Junction temperature = ambient for +25
C specifications.
(2) Junction temperature = ambient at low temperature limit; junction temperature = ambient +23
C at high temperature limit for over temperature
specifications.
(3) Test levels: (A) 100% tested at +25
C. Over temperature limits by characterization and simulation. (B) Limits set by characterization and
simulation. (C) Typical value only for information.
(4) Current considered positive out of node. VCM is the input common-mode voltage.
(5) Tested < 3dB below minimum CMRR at min/max input ranges.
OPA2674
SBOS270 - AUGUST 2003
www.ti.com
7
TYPICAL CHARACTERISTICS: V
S
=
6V
At TA = +25
C, G = +4, RF = 402
, and RL = 100
, unless otherwise noted.
NONINVERTING SMALL-SIGNAL
FREQUENCY RESPONSE OVER GAIN
Frequency (MHz)
0
100
200
300
400
500
3
0
-
3
-
6
-
9
-
12
-
15
N
o
r
m
al
i
z
ed
G
a
i
n
(
d
B
)
V
O
= 0.5V
PP
See Figure 1
G = +8, R
F
= 250
G = +2,
R
F
= 475
G = +4, R
F
= 402
G = +1, R
F
= 511
INVERTING SMALL-SIGNAL
FREQUENCY RESPONSE OVER GAIN
Frequency (MHz)
0
100
200
300
400
500
3
0
-
3
-
6
-
9
-
12
-
15
N
o
r
m
al
i
z
ed
G
a
i
n
(
d
B
)
V
O
= 0.5V
PP
See Figure 2
G =
-
1, R
F
= 475
G =
-
2, R
F
= 422
G =
-
8, R
F
= 402
G =
-
4, R
F
= 402
NONINVERTING SMALL-SIGNAL
FREQUENCY RESPONSE OVER POWER SETTINGS
Frequency (MHz)
0
100
200
300
400
500
15
12
9
6
3
0
-
3
-
6
Ga
i
n
(
d
B
)
G = +4
V
O
= 0.5V
PP
Power Cutback
Idle Power
Full Power
See Figure 1
INVERTING SMALL-SIGNAL
FREQUENCY RESPONSE OVER POWER SETTINGS
Frequency (MHz)
0
100
200
300
400
500
15
12
9
6
3
0
-
3
-
6
Ga
i
n
(
d
B
)
G =
-
4
V
O
= 0.5V
PP
Power Cutback
Idle Power
Full Power
See Figure 2
NONINVERTING LARGE-SIGNAL
FREQUENCY RESPONSE
Frequency (MHz)
0
100
200
300
400
500
15
12
9
6
3
0
-
3
-
6
Ga
i
n
(
d
B
)
G = +4
V
O
= 8V
PP
V
O
= 10V
PP
V
O
= 2V
PP
V
O
1V
PP
See Figure 1
INVERTING LARGE-SIGNAL
FREQUENCY RESPONSE
Frequency (MHz)
0
100
200
300
400
500
15
12
9
6
3
0
-
3
-
6
Ga
i
n
(
d
B
)
G =
-
4
V
O
= 8V
PP
V
O
= 10V
PP
V
O
= 5V
PP
V
O
1V
PP
See Figure 2
OPA2674
SBOS270 - AUGUST 2003
www.ti.com
8
TYPICAL CHARACTERISTICS: V
S
=
6V (continued)
At TA = +25
C, G = +4, RF = 402
, and RL = 100
, unless otherwise noted.
NONINVERTING PULSE RESPONSE
Time (5ns/div)
O
u
tput
V
o
l
t
age
(
1
V
/
d
i
v
)
O
u
tp
ut
V
o
l
t
a
g
e
(
100
mV
/
d
i
v
)
4V
PP
G = +4
R
L
= 100
200mV
PP
Left Scale
Large Signal
Right Scale
Small Signal
See Figure 1
NONINVERTING PULSE RESPONSE
Time (5ns/div)
O
u
tput
V
o
l
t
age
(
1
V
/
d
i
v
)
O
u
tp
ut
V
o
l
t
a
g
e
(
100
mV
/
d
i
v
)
4V
PP
G = +4
R
L
= 100
200mV
PP
Left Scale
Large Signal
Right Scale
Small Signal
See Figure 1
HARMONIC DISTORTION vs FREQUENCY
Frequency (MHz)
0.1
1
20
10
-
60
-
65
-
70
-
75
-
80
-
85
-
90
-
95
-
100
-
105
H
a
rm
o
n
i
c
D
i
s
t
o
rt
i
o
n
(
d
B
c
)
G = +4
V
O
= 2V
PP
R
L
= 100
Single Channel, See Figure 1
2nd-Harmonic
3rd-Harmonic
HARMONIC DISTORTION vs OUTPUT VOLTAGE
Output Voltage (V
PP
)
0.1
1
10
-
50
-
60
-
70
-
80
-
90
-
100
H
a
rm
o
n
i
c
D
i
s
t
o
rt
i
o
n
(
d
B
c
)
f = 5MHz
R
L
= 100
2nd-Harmonic
3rd-Harmonic
Single Channel, See Figure 1
HARMONIC DISTORTION vs NONINVERTING GAIN
Gain Magnitude (V/V)
1
-
60
-
65
-
70
-
75
-
80
-
85
-
90
10
H
a
rm
o
n
i
c
D
i
s
t
o
rt
i
o
n
(
d
B
c
)
V
O
= 2V
PP
f = 5MHz
R
L
= 100
2nd-Harmonic
3rd-Harmonic
Single Channel, See Figure 1
HARMONIC DISTORTION vs INVERTING GAIN
Gain Magnitude (
-
V/V)
1
-
60
-
65
-
70
-
75
-
80
-
85
-
90
10
H
a
rm
o
n
i
c
D
i
s
t
o
rt
i
o
n
(
d
B
c
)
V
O
= 2V
PP
f = 5MHz
R
L
= 100
2nd-Harmonic
3rd-Harmonic
Single Channel, See Figure 2
OPA2674
SBOS270 - AUGUST 2003
www.ti.com
9
TYPICAL CHARACTERISTICS: V
S
=
6V (continued)
At TA = +25
C, G = +4, RF = 402
, and RL = 100
, unless otherwise noted.
HARMONIC DISTORTION vs LOAD RESISTANCE
Load Resistance (
)
10
-
50
-
55
-
60
-
65
-
70
-
75
-
80
-
85
-
90
-
95
-
100
100
1k
Ha
r
m
o
n
i
c
Di
s
t
o
r
t
i
o
n
(
d
B
c
)
Single Channel, See Figure 1
V
O
= 2V
PP
f = 5MHz
2nd-Harmonic
3rd-Harmonic
2-TONE, 3rd-ORDER SPURIOUS LEVEL
Single-Tone Load Power (dBm)
-
10
0
5
-
5
10
-
60
-
65
-
70
-
75
-
80
-
85
-
90
-
95
-
100
3r
d-
O
r
de
r
S
pur
i
o
us
Lev
el
(
d
B
c
)
20MHz
5MHz
1MHz
Power at Matched 50
Load, See Figure 1
10MHz
dBc = dB Below Carriers
MAXIMUM OUTPUT SWING vs LOAD RESISTANCE
Load Resistance (
)
10
100
1k
6
5
4
3
2
1
0
-
1
-
2
-
3
-
4
-
5
-
6
O
u
t
p
u
t
Vo
l
t
a
g
e
(
V)
OUTPUT VOLTAGE AND CURRENT LIMITATIONS
I
O
(mA)
-
600
6
5
4
3
2
1
0
-
1
-
2
-
3
-
4
-
5
-
6
0
200
400
-
200
-
400
600
V
O
(V
)
R
L
= 10
R
L
= 25
R
L
= 50
R
L
= 100
1 W In terna l P ow er
S ingle C ha nnel
1 W In ternal P ow er
Single Ch ann el
INPUT VOLTAGE AND CURRENT NOISE DENSITY
Frequency (Hz)
100
100
10
1
100k
1M
10k
1k
10M
V
o
l
t
age
N
o
i
s
e
(
n
V
/
Hz
)
C
u
r
r
en
t
N
oi
s
e
(
p
A
/
Hz
)
Inverting Current N oise
Noninverting Current Noise
Voltage Noise
2.0nV/
Hz
16pA/
H z
24pA/
Hz
CHANNEL-TO-CHANNEL CROSSTALK
Frequency (Hz)
1M
10M
100M
-
60
-
65
-
70
-
75
-
80
-
85
-
90
-
95
-
100
-
105
-
110
C
r
os
s
t
al
k
,
I
nput
R
e
fer
r
e
d
(
d
B
)
Input Referred
OPA2674
SBOS270 - AUGUST 2003
www.ti.com
10
TYPICAL CHARACTERISTICS: V
S
=
6V (continued)
At TA = +25
C, G = +4, RF = 402
, and RL = 100
, unless otherwise noted.
RECOMMENDED R
S
vs CAPACITIVE LOAD
Capacitive Load (pF)
1
10
100
1k
90
80
70
60
50
40
30
20
10
0
R
S
(
)
FREQUENCY RESPONSE vs CAPACITIVE LOAD
Frequency (Hz)
1M
2
0
-
2
-
4
-
6
-
8
-
10
10M
100M
1G
N
o
r
m
al
i
z
ed
G
a
i
n
to
C
apac
i
t
i
v
e
L
oad
(
d
B
)
C
L
= 10pF
C
L
= 22pF
C
L
= 100pF
C
L
= 47pF
1/2
OPA2674
402
R
S
133
1k
(1)
C
L
NOTE: (1) 1k
is optional.
CMRR AND PSRR vs FREQUENCY
Frequency (Hz)
1k
70
60
50
40
30
20
10
0
10k
100k
1M
10M
100M
Po
w
e
r
-
S
u
ppl
y
R
e
j
ec
ti
o
n
R
a
t
i
o
(
dB
)
C
o
m
m
on-
M
o
d
e
R
e
j
e
c
t
i
o
n
R
ati
o
(
d
B
)
CMRR
-
PSRR
+PSRR
OPEN-LOOP TRANSIMPEDANCE GAIN AND PHASE
Frequency (Hz)
10k
100k
1M
10M
100M
1G
120
100
80
60
40
20
0
T
r
ans
i
m
p
e
dan
c
e
G
a
i
n
(
d
B
)
0
-
45
-
90
-
135
-
180
-
225
-
270
T
r
a
n
s
i
m
p
ed
an
c
e
P
h
a
s
e
(
_
)
Gain
Phase
CLOSED-LOOP OUTPUT IMPEDANCE
vs FREQUENCY
Frequency (Hz)
100k
1M
10M
100M
100
10
1
0.1
0.01
0.001
O
u
t
p
u
t
R
e
si
st
a
n
ce
(
)
Idle Power
Full Power
Power Cutback
COMPOSITE VIDEO dG/dP
Number of 150
Loads
1
2
3
4
5
6
7
8
9
10
0.10
0.09
0.08
0.07
0.06
0.05
0.04
0.03
0.02
0.01
0
dG
/
d
P
(
%
/
_
)
G = +2
R
F
= 475
V
S
=
5V
dP, Negative Video
dP, Positive Video
dG, Positive Video
dG , Negative V ideo
OPA2674
SBOS270 - AUGUST 2003
www.ti.com
11
TYPICAL CHARACTERISTICS: V
S
=
6V (continued)
At TA = +25
C, G = +4, RF = 402
, and RL = 100
, unless otherwise noted.
16
12
8
4
0
-
4
-
8
-
12
-
16
NONINVERTING OVERDRIVE RECOVERY
Time (25ns/div)
O
u
tput
V
o
l
t
age
(
V
)
4
3
2
1
0
-
1
-
2
-
3
-
4
In
put
V
o
l
t
age
(
V
)
G = +4
R
L
= 100
See Figure 1
Input
Output
16
12
8
4
0
-
4
-
8
-
12
-
16
INVERTING OVERDRIVE RECOVERY
Time (25ns/div)
O
u
tpu
t
V
o
l
t
age
(
V
)
4
3
2
1
0
-
1
-
2
-
3
-
4
I
nput
V
o
l
t
age
(
V
)
Input
Output
G =
-
4
R
L
= 100
See Figure 2
TYPICAL DC DRIFT OVER TEMPERATURE
Ambient Temperature (
_
C)
-
50
14
12
10
8
6
4
2
0
-
2
-
4
-
6
-
8
-
10
-
12
-
14
-
25
0
25
50
75
100
125
Inp
u
t
O
ffs
e
t
V
o
l
t
ag
e
(
m
V
)
I
n
p
u
t
B
i
a
s
C
ur
r
ent
(
A)
Noninverting Bias Current
Input Offset Voltage
Inverting Bias Current
SUPPLY AND OUTPUT CURRENT vs TEMPERATURE
Temperature (
_
C)
-
50
750
700
650
600
550
500
450
400
350
300
250
-
25
0
25
50
75
100
125
O
u
tput
C
u
r
r
e
n
t
(
mA
)
20
18
16
14
12
10
8
6
4
2
0
S
u
ppl
y
C
u
r
r
e
n
t
,
B
o
t
h
C
ha
nnel
s
(
m
A
)
Sourcing Output Current
Sinking Output Current
Supply Current, Full Power
Supply Current, Power Cutback
Supply Current, Idle Power
COMMON-MODE INPUT VOLTAGE RANGE
AND OUTPUT SWING vs SUPPLY VOLTAGE
Supply Voltage (
V)
2
3
4
5
6
5
4
3
2
1
0
6
V
o
l
t
ag
e
R
an
g
e
(
V)
Negative Output Swing
Negative Common-Mode Input Voltage
Positive Common-Mode Input Voltage
Positive Output Swing
OPA2674
SBOS270 - AUGUST 2003
www.ti.com
12
TYPICAL CHARACTERISTICS: V
S
=
6V
At TA = +25
C, Differential Gain = +9, RF = 300
, and RL = 70
, unless otherwise noted. See Figure 5 for AC performance only.
DIFFERENTIAL SMALL-SIGNAL
FREQUENCY RESPONSE
Frequency (MHz)
0
250
50
100
150
200
300
3
0
-
3
-
6
-
9
-
12
-
15
No
r
m
a
l
i
z
e
d
G
a
i
n
(
d
B
)
R
L
= 70
V
O
= 1V
PP
See Figure 5
G
D
= +2,
R
F
= 442
G
D
= +5,
R
F
= 383
G
D
= +9,
R
F
= 300
DIFFERENTIAL LARGE-SIGNAL
FREQUENCY RESPONSE
Frequency (MHz)
0
250
50
100
150
200
300
22
19
16
13
10
7
4
1
Ga
i
n
(d
B
)
16V
PP
R
L
= 70
G
D
= +9
See Figure 5
8V
PP
4V
PP
1V
PP
DIFFERENTIAL DISTORTION vs LOAD RESISTANCE
Load Resistance (
)
10
1k
100
-
60
-
65
-
70
-
75
-
80
-
85
-
90
-
95
-
100
-
105
-
110
H
a
r
m
on
i
c
D
i
s
t
o
r
t
i
on
(
d
B
)
2nd-Harmonic
3rd-Harmonic
f = 500kHz
G = +9
R
L
= 70
V
O
= 4V
PP
See Figure 5
DIFFERENTIAL DISTORTION vs FREQUENCY
Frequency (MHz)
0.1
10
1
100
-
50
-
65
-
70
-
80
-
90
-
100
-
110
H
a
rm
o
n
i
c
D
i
s
t
o
rt
i
o
n
(
d
B
)
2nd-Harmonic
3rd-Harmonic
G = +9
R
L
= 70
See Figure 5
DIFFERENTIAL DISTORTION vs OUTPUT VOLTAGE
Differential Output Voltage (V
PP
)
0.1
10
1
20
-
60
-
70
-
80
-
90
-
100
-
110
Ha
r
m
o
n
i
c
Di
s
t
o
r
ti
o
n
(
d
B
c
)
f = 500kHz
G = +9
R
L
= 70
2nd-Harmonic
3rd-Harmonic
See Figure 5
ADSL MULTITONE POWER RATIO
(Upstream)
Frequency (kHz)
0
40
20
80
60
120
140
100
160
0
-
10
-
20
-
30
-
40
-
50
-
60
-
70
-
80
-
90
-
100
Po
w
e
r
(
d
B
m
)
V
S
=
6V
See Figure 5
OPA2674
SBOS270 - AUGUST 2003
www.ti.com
13
TYPICAL CHARACTERISTICS: V
S
= +5V
At TA = +25
C, G = +4, RF = 453
, and RL = 100
, unless otherwise noted.
NONINVERTING SMALL-SIGNAL
FREQUENCY RESPONSE
Frequency (MHz)
0
100
200
300
400
500
3
0
-
3
-
6
-
9
-
12
-
15
-
18
N
o
r
m
al
i
z
ed
G
a
i
n
(
d
B
)
See Figure 3
G = +1
R
F
= 549
G = +2
R
F
= 511
G = +4
R
F
= 453
G = +8
R
F
= 332
INVERTING SMALL-SIGNAL
FREQUENCY RESPONSE
Frequency (MHz)
0
100
200
300
400
500
3
0
-
3
-
6
-
9
-
12
-
15
-
18
N
o
r
m
al
i
z
ed
G
a
i
n
(
d
B
)
See Figure 4
G =
-
1
R
F
= 549
G =
-
2
R
F
= 511
G =
-
4
R
F
= 453
G =
-
8
R
F
= 402
NONINVERTING LARGE-SIGNAL
FREQUENCY RESPONSE
Frequency (MHz)
0
100
200
300
400
500
15
12
9
6
3
0
-
3
-
6
Ga
i
n
(
d
B
)
V
O
= 3V
PP
V
O
= 1V
PP
V
O
= 2V
PP
G = +4
R
L
= 100
to V
S
/2
See Figure 3
INVERTING LARGE-SIGNAL
FREQUENCY RESPONSE
Frequency (MHz)
0
100
200
300
400
500
15
12
9
6
3
0
-
3
-
6
Ga
i
n
(
d
B
)
V
O
= 3V
PP
V
O
= 1V
PP
V
O
= 2V
PP
G =
-
4
R
L
= 100
to V
S
/2
See Figure 4
NONINVERTING PULSE RESPONSE
Time (5ns/div)
O
u
t
p
ut
V
o
l
t
a
g
e
(
0.
5
V
/d
i
v
)
I
n
p
u
t
V
o
l
ta
ge
(
1
00
mV
/
d
i
v
)
2V
PP
Large Signal
200mV
PP
Small Signal
Left Scale
Right Scale
G = +4
R
L
= 100
to V
S
/2
See Figure 3
INVERTING PULSE RESPONSE
Time (5ns/div)
O
u
t
p
ut
V
o
l
t
a
g
e
(
0.
5
V
/d
i
v
)
I
n
p
u
t
V
o
l
ta
ge
(
1
00
mV
/
d
i
v
)
2V
PP
Large Signal
200mV
PP
Small Signal
Left Scale
Right Scale
G =
-
4
R
L
= 100
to V
S
/2
See Figure 4
OPA2674
SBOS270 - AUGUST 2003
www.ti.com
14
TYPICAL CHARACTERISTICS: V
S
= +5V (continued)
At TA = +25
C, G = +4, RF = 453
, and RL = 100
, unless otherwise noted.
HARMONIC DISTORTION vs FREQUENCY
Frequency (MHz)
0.1
1
20
10
-
50
-
55
-
60
-
65
-
70
-
75
-
80
-
85
-
90
Ha
r
m
o
n
i
c
Di
s
t
o
r
t
i
o
n
(
d
B
c
)
V
O
= 2V
PP
G = +4
R
L
= 100
to V
S
/2
Single Channel, See Figure 3
2nd-Harmonic
3rd-Harmonic
HARMONIC DISTORTION vs OUTPUT VOLTAGE
Output Voltage (V
PP
)
0.1
1
5
-
60
-
65
-
70
-
75
-
80
-
85
-
90
H
a
r
m
oni
c
D
i
s
t
o
r
t
i
o
n
(
d
B
c
)
f = 5MHz
R
L
= 100
to V
S
/2
Single Channel, See Figure 3
3rd-Harmonic
2nd-Harmonic
HARMONIC DISTORTION vs NONINVERTING GAIN
Gain Magnitude (V/V)
1
-
55
-
60
-
65
-
70
-
75
-
80
-
85
10
Ha
r
m
o
n
i
c
Di
s
t
o
r
ti
o
n
(
d
B
c
)
2nd-Harmonic
3rd-Harmonic
V
O
= 2V
PP
f = 5MHz
R
L
= 100
to V
S
/2
Single Channel, See Figure 3
HARMONIC DISTORTION vs INVERTING GAIN
Gain (
-
V/V)
1
-
55
-
60
-
65
-
70
-
75
-
80
-
85
10
Ha
r
m
o
n
i
c
Di
s
t
o
r
ti
o
n
(
d
B
c
)
2nd-Harmonic
3rd-Harmonic
V
O
= 2V
PP
f = 5MHz
R
L
= 100
to V
S
/2
Single Channel, See Figure 4
HARMONIC DISTORTION vs LOAD RESISTANCE
Load Resistance (
)
10
100
1k
-
40
-
45
-
50
-
55
-
60
-
65
-
70
-
75
-
80
-
85
-
90
H
a
rm
o
n
i
c
D
i
s
t
o
rt
i
o
n
(
d
B
c
)
Single Channel, See Figure 3
V
O
= 2V
PP
f = 5MHz
R
L
= 100
to V
S
/2
2nd-Harmonic
3rd-Harmonic
2-TONE, 3rd-ORDER SPURIOUS LEVEL
Single-Tone Load Power (dBm)
-
14
-
6
-
2
-
10
2
-
8
-
4
-
12
0
-
55
-
60
-
65
-
70
-
75
-
80
-
85
-
90
-
95
3r
d
-
O
r
der
S
p
ur
i
o
u
s
L
e
v
e
l
(
dB
c
)
Single Channel. See Figure 3.
Power at matched 50
load.
20MHz
5MHz
1MHz
10MHz
OPA2674
SBOS270 - AUGUST 2003
www.ti.com
15
TYPICAL CHARACTERISTICS: V
S
= +5V
At TA = +25
C, Differential Gain = +9, RF = 316
, and RL = 70
, unless otherwise noted.
DIFFERENTIAL PERFORMANCE
TEST CIRCUIT
R
L
R
F
316
R
G
C
G
R
F
316
V
O
V
I
G
D=
1+2
R
F
R
G
=
V
O
V
I
+5V
DIFFERENTIAL SMALL-SIGNAL
FREQUENCY RESPONSE
Frequency (MHz)
0
50
100
150
200
250
300
3
0
-
3
-
6
-
9
-
12
-
15
N
o
rm
a
l
i
z
e
d
G
a
i
n
(d
B
)
G
D
= +2
R
F
= 511
G
D
= +5
R
F
= 422
G
D
= +9
R
F
= 316
R
L
= 70
DIFFERENTIAL LARGE-SIGNAL
FREQUENCY RESPONSE
Frequency (MHz)
0
50
100
150
200
250
300
22
19
16
13
10
7
4
1
Ga
i
n
(
d
B
)
4V
PP
1V
PP
2V
PP
5V
PP
R
L
= 70
G
D
= +9
HARMONIC DISTORTION vs LOAD RESISTANCE
Load Resistance (
)
10
1k
100
-
60
-
65
-
70
-
75
-
80
-
85
-
90
-
95
-
100
H
a
r
m
oni
c
D
i
s
t
o
r
t
i
o
n
(
dB
c
)
2nd-Harmonic
3rd-Harmonic
G
D
= +9
R
L
= 70
f = 500kHz
V
O
= 4V
PP
DIFFERENTIAL DISTORTION vs FREQUENCY
Frequency (MHz)
0.1
10
1
100
-
50
-
60
-
70
-
80
-
90
-
100
Ha
r
m
o
n
i
c
Di
s
t
o
r
ti
o
n
(
d
B
c
)
3rd-Harmonic
2nd-Harmonic
G
D
= +9
R
L
= 70
HARMONIC DISTORTION vs OUTPUT VOLTAGE
Output Voltage (V
PP
)
1
10
-
60
-
70
-
80
-
90
-
100
Ha
r
m
o
n
i
c
Di
s
t
o
r
ti
o
n
(
d
B
)
G
D
= +9
R
L
= 70
f = 500kHz
2nd-Harmonic
3rd-Harmonic
OPA2674
SBOS270 - AUGUST 2003
www.ti.com
16
APPLICATION INFORMATION
WIDEBAND CURRENT-FEEDBACK OPERATION
The OPA2674 gives the exceptional AC performance of a
wideband current-feedback op amp with a highly linear,
high-power output stage. Requiring only 9mA/ch
quiescent current, the OPA2674 swings to within 1V of
either supply rail and delivers in excess of 380mA at room
temperature. This low output headroom requirement,
along with supply voltage independent biasing, gives
remarkable single (+5V) supply operation. The OPA2674
delivers greater than 150MHz bandwidth driving a 2V
PP
output into 100
on a single +5V supply. Previous boosted
output stage amplifiers typically suffer from very poor
crossover distortion as the output current goes through
zero. The OPA2674 achieves a comparable power gain
with much better linearity. The primary advantage of a
current-feedback op amp over a voltage-feedback op amp
is that AC performance (bandwidth and distortion) is
relatively independent of signal gain. Figure 1 shows the
DC-coupled, gain of +4, dual power-supply circuit
configuration used as the basis of the
6V Electrical and
Typical Characteristics. For test purposes, the input
impedance is set to 50
with a resistor to ground and the
output impedance is set to 50
with a series output
resistor. Voltage swings reported in the electrical
characteristics are taken directly at the input and output
pins whereas load powers (dBm) are defined at a matched
50
load. For the circuit of Figure 1, the total effective load
is 100
|| 535
= 84
.
1/2
OPA2674
+6V
+
-
6V
50
Load
50
50
V
O
V
I
50
Source
R
G
133
R
F
402
+
6.8
F
0.1
F
6.8
F
0.1
F
+V
S
-
V
S
Figure 1. DC-Coupled, G = +4, Bipolar Supply,
Specification and Test Circuit
Figure 2 shows the DC-coupled, bipolar supply circuit
inverting gain configuration used as the basis for the
6V
Electrical and Typical Characteristics. Key design
considerations of the inverting configuration are
developed in the Inverting Amplifier Operation discussion.
1/2
OPA2674
+6V
-
6V
50
Load
50
V
O
V
I
50
Source
R
M
100
R
F
402
R
G
100
Power-supply
decoupling
not shown.
Figure 2. DC-Coupled, G = -4, Bipolar Supply,
Specification and Test Circuit
Figure 3 shows the AC coupled, gain of +4, single-supply
circuit configuration used as the basis of the +5V Electrical
and Typical Characteristics. Though not a rail-to-rail
design, the OPA2674 requires minimal input and output
voltage headroom compared to other wideband
current-feedback op amps. It will deliver a 3V
PP
output
swing on a single +5V supply with greater than 100MHz
bandwidth. The key requirement of broadband single-
supply operation is to maintain input and output signal
swings within the usable voltage ranges at both the input
and the output. The circuit of Figure 3 establishes an input
midpoint bias using a simple resistive divider from the +5V
supply (two 806
resistors). The input signal is then
AC-coupled into this midpoint voltage bias. The input
voltage can swing to within 1.3V of either supply pin, giving
a 2.4V
PP
input signal range centered between the supply
pins. The input impedance matching resistor (57.6
) used
for testing is adjusted to give a 50
input match when the
parallel combination of the biasing divider network is
included. The gain resistor (R
G
) is AC-coupled, giving the
circuit a DC gain of +1
which puts the input DC bias
voltage (2.5V) on the output as well. The feedback resistor
value is adjusted from the bipolar supply condition to
re-optimize for a flat frequency response in +5V, gain of +4,
operation. Again, on a single +5V supply, the output
voltage can swing to within 1V of either supply pin while
delivering more than 200mA output current. A demanding
100
load to a midpoint bias is used in this
characterization circuit. The new output stage used in the
OPA2674 can deliver large bipolar output currents into this
midpoint load with minimal crossover distortion, as shown
by the +5V supply, harmonic distortion plots in the Typical
Characteristics charts.
OPA2674
SBOS270 - AUGUST 2003
www.ti.com
17
1/2
OPA2674
+5V
+V
S
V
S
/2
806
100
V
O
V
I
57.6
806
R
F
453
R
G
150
0.1
F
0.1
F
6.8
F
+
0.1
F
Figure 3. AC-Coupled, G = +4, Single-Supply,
Specification and Test Circuit
The last configuration used as the basis of the +5V
Electrical and Typical Characteristics is shown in Figure 4.
Design considerations for this inverting, bipolar supply
configuration are covered either in single-supply
configuration (as shown in Figure 3) or in the Inverting
Amplifier Operation discussion.
1/2
OPA2674
+5V
V
S
/2
806
V
I
100
V
O
806
R
F
453
R
M
88.7
6.8
F
+
0.1
F
0.1
F
R
G
113
Figure 4. AC-Coupled, G = -4, Single-Supply,
Specification and Test Circuit
SINGLE-SUPPLY ADSL UPSTREAM DRIVER
Figure 5 shows a single-supply ADSL upstream driver.
The dual OPA2674 is configured as a differential gain
stage to provide signal drive to the primary of the
transformer (here, a step-up transformer with a turns ratio
of 1:1.7). The main advantage of this configuration is the
reduction of even-order harmonic distortion products.
Another important advantage for ADSL is that each
amplifier needs only half of the total output swing required
to drive the load.
R
G
82.5
2k
2k
1
F
0.1
F
0.1
F
17.4
R
M
100
AFE
2V
PP
Max
Assumed
R
F
324
20
20
R
F
324
1/2
OP A2674
1/2
OP A2674
+12V
1:1.7
17.7V
PP
I
P
= 128mA
I
P
= 128mA
17.4
R
M
+6V
Z
Line
Figure 5. Single-Supply ADSL Upstream Driver
The analog front-end (AFE) signal is AC-coupled to the
driver and the noninverting input of each amplifier is biased
to the mid-supply voltage (in this case, +6V). Furthermore,
by providing the proper biasing to the amplifier, this
scheme also provides high-pass filtering with a corner
frequency set here at 5kHz. As the upstream signal
bandwidth starts at 26kHz, this high-pass filter does not
generate any problems and has the advantage of filtering
out unwanted lower frequencies.
The input signal is amplified with a gain set by the following
equation:
G
D
+
1
)
2
R
F
R
G
With R
F
= 324
and R
G
= 82.5
, the gain for this
differential amplifier is 8.85. This gain boosts the AFE
signal, assumed to be a maximum of 2V
PP
, to a maximum
of 17.7V
PP
.
Refer to the Setting Resistor Values to Optimize
Bandwidth section for a discussion on which feedback
resistor value to choose.
The two back-termination resistors (17.4
each) added at
each input of the transformer make the impedance of the
modem match the impedance of the phone line, and also
provide a means of detecting the received signal for the
receiver. The value of these resistors (R
M
) is a function of
the line impedance and the transformer turns ratio (n),
given by the following equation:
R
M
+
Z
LINE
2n
2
(1)
(2)
OPA2674
SBOS270 - AUGUST 2003
www.ti.com
18
OPA2674 HDSL2 UPSTREAM DRIVER
Figure 6 shows an HDSL2 implementation of a single-
supply driver.
82.5
2k
2k
1
F
0.1
F
0.1
F
11.5
135
AFE
2V
PP
Max
Assumed
324
20
20
324
1/2
OPA 2674
1/2
OPA 2674
+12V
1:2.4
17.7V
PP
I
P
= 185mA
I
P
= 185mA
11.5
+6V
Z
Line
Figure 6. HDSL2 Upstream Driver
The two designs differ by the values of the matching
impedance, the load impedance, and the ratio turns of the
transformers. All of these differences are reflected in the
higher peak current and thus, the higher maximum power
dissipation in the output of the driver.
LINE DRIVER HEADROOM MODEL
The first step in a driver design is to compute the
peak-to-peak output voltage from the target specifications.
This is done using the following equations:
P
L
+
10
log
V
RMS
2
(1mW)
R
L
With P
L
power and V
RMS
voltage at the load, and R
L
load
impedance, this gives:
V
RMS
+
(1mW)
R
L
10
P
L
10
V
P
+
CrestFactor
V
RMS
+
CF
V
RMS
with V
P
peak voltage at the load and CF Crest Factor;
V
LPP
+
2
CF
V
RMS
with V
LPP
: peak-to-peak voltage at the load.
Consolidating Equations 3 through 6 allows the required
peak-to-peak voltage at the load function of the crest
factor, the load impedance, and the power in the load to be
expressed. Thus:
V
LPP
+
2
CF
(1mW)
R
L
10
P
L
10
This V
LPP
is usually computed for a nominal line
impedance and may be taken as a fixed design target.
The next step for the driver is to compute the individual
amplifier output voltage and currents as a function of V
PP
on the line and transformer turns ratio. As the turns ratio
changes, the minimum allowed supply voltage also
changes. The peak current in the amplifier is given by:
"
I
P
+
1
2
2
V
LPP
n
1
4R
M
With V
LPP
defined in Equation 7 and R
M
defined in
Equation 2. The peak current is computed in Figure 7 by
noting that the total load is 4R
M
and that the peak current
is half of the peak-to-peak calculated using V
LPP
.
R
M
R
M
V
LPP
n
V
LPP
R
L
I
P
I
P
2V
LPP
n
1:n
Figure 7. Driver Peak Output Model
With the required output voltage and current versus turns
ratio set, an output stage headroom model will allow the
required supply voltage versus turns ratio to be developed.
The headroom model (see Figure 8) can be described with
the following set of equations:
First, as available output voltage for each amplifier:
V
OPP
+
V
CC
*
(V
1
)
V
2
)
*
I
P
(R
1
)
R
2
)
Or, second, as required single-supply voltage:
V
CC
+
V
OPP
)
(V
1
)
V
2
)
)
I
P
(R
1
)
R
2
)
The minimum supply voltage for a power and load
requirement is given by Equation 10.
(3)
(4)
(5)
(6)
(7)
(8)
(9)
(10)
OPA2674
SBOS270 - AUGUST 2003
www.ti.com
19
V
O
R
1
V
1
+V
CC
R
2
V
2
I
P
Figure 8. Line Driver Headroom Model
Table 1 gives V
1
, V
2
, R
1
, and R
2
for both +12V and +5V
operation of the OPA2674.
Table 1. Line Driver Headroom Model Values
V1
R1
V2
R2
+5V
0.9V
5
0.8V
5
+12V
0.9V
2
0.9V
2
TOTAL DRIVER POWER FOR xDSL
APPLICATIONS
The total internal power dissipation for the OPA2674 in an
xDSL line driver application will be the sum of the
quiescent power and the output stage power. The
OPA2674 holds a relatively constant quiescent current
versus supply voltage--giving a power contribution that is
simply the quiescent current times the supply voltage used
(the supply voltage will be greater than the solution given
in Equation 10). The total output stage power may be
computed with reference to Figure 9.
R
T
+V
CC
I
AVG
=
I
P
C
F
Figure 9. Output Stage Power Model
The two output stages used to drive the load of Figure 7
can be seen as an H-Bridge in Figure 9. The average
current drawn from the supply into this H-Bridge and load
will be the peak current in the load given by Equation 8
divided by the crest factor (CF) for the xDSL modulation.
This total power from the supply is then reduced by the
power in R
T
to leave the power dissipated internal to the
drivers in the four output stage transistors. That power is
simply the target line power used in Equation 2 plus the
power lost in the matching elements (R
M
). In the examples
here, a perfect match is targeted giving the same power in
the matching elements as in the load. The output stage
power is then set by Equation 11.
P
OUT
+
I
P
C
F
V
CC
*
2P
L
The total amplifier power is then:
P
TOT
+
I
q
V
CC
)
I
P
C
F
V
CC
*
2P
L
For the ADSL CPE upstream driver design of Figure 5, the
peak current is 128mA for a signal that requires a crest
factor of 5.33 with a target line power of 13dBm into 100
(20mW). With a typical quiescent current of 18mA and a
nominal supply voltage of +12V, the total internal power
dissipation for the solution of Figure 5 will be:
P
TOT
+
18mA(12V)
)
128mA
5.33
(12V)
*
2(20mW)
+
464mW
DESIGN-IN TOOLS
DEMONSTRATION BOARDS
Several PC boards are available to assist in the initial
evaluation of circuit performance using the OPA2674 in
the two package styles. These are available, free, as
unpopulated PC boards delivered with descriptive
documentation. Table 2 shows the summary information
for these boards.
Table 2. Demo Board Availability
PRODUCT
PACKAGE
DEMO BOARD
ORDERING
PRODUCT
PACKAGE
DEMO BOARD
NUMBER
ORDERING
NUMBER
OPA2674ID
SO-8
DEM
-
OPA268XU
SBOU003
OPA2674I-14D
SO-14
DEM
-
OPA268XN
SBOU002
Go to the TI web site (www.ti.com) to request either of
these boards.
MACROMODELS AND APPLICATIONS
SUPPORT
Computer simulation of circuit performance using SPICE
is often useful when analyzing the performance of analog
circuits and systems. This is particularly true for video and
RF amplifier circuits where parasitic capacitance and
(11)
(12)
(13)
OPA2674
SBOS270 - AUGUST 2003
www.ti.com
20
inductance can have a major effect on circuit performance.
A SPICE model for the OPA2674 is available through the
TI web site (www.ti.com). This model does a good job of
predicting small-signal AC and transient performance
under a wide variety of operating conditions, but does not
do as well in predicting the harmonic distortion or dG/dP
characteristics. This model does not attempt to distinguish
between the package types in small-signal AC
performance, nor does it attempt to simulate channel-to-
channel coupling.
OPERATING SUGGESTIONS
SETTING RESISTOR VALUES TO OPTIMIZE
BANDWIDTH
A current-feedback op amp such as the OPA2674 can hold
an almost constant bandwidth over signal gain settings
with the proper adjustment of the external resistor values,
which are shown in the Typical Characteristics; the
small-signal bandwidth decreases only slightly with
increasing gain. These characteristic curves also show
that the feedback resistor is changed for each gain setting.
The resistor values on the inverting side of the circuit for a
current-feedback op amp can be treated as frequency
response compensation elements, whereas the ratios set
the signal gain. Figure 10 shows the small-signal
frequency response analysis circuit for the OPA2674.
V
O
R
G
V
I
R
I
Z
(S)
I
ERR
R
F
I
ERR
Figure 10. Current-Feedback Transfer Function
Analysis Circuit
The key elements of this current-feedback op amp model
are:
= buffer gain from the noninverting input to the
inverting input
R
I
= buffer output impedance
I
ERR
= feedback error current signal
Z(s) = frequency dependent open
-
loop transimpe-
dance gain from I
ERR
to V
O
NG
+
NoiseGain
+
1
)
R
F
R
G
The buffer gain is typically very close to 1.00 and is normal-
ly neglected from signal gain considerations. This gain,
however, sets the CMRR for a single op amp differential
amplifier configuration. For a buffer gain of
< 1.0, the
CMRR = -20
log(1 -
)dB.
R
I
, the buffer output impedance, is a critical portion of the
bandwidth control equation. The OPA2674 inverting
output impedance is typically 22
.
A current-feedback op amp senses an error current in the
inverting node (as opposed to a differential input error
voltage for a voltage-feedback op amp) and passes this on
to the output through an internal frequency dependent
transimpedance gain. The Typical Characteristics show
this open-loop transimpedance response, which is
analogous to the open-loop voltage gain curve for a
voltage-feedback op amp. Developing the transfer
function for the circuit of Figure 10 gives Equation 14:
V
O
V
I
+
a
1
)
R
F
R
G
1
)
R
F
)
R
I
1
)
R
F
R
G
Z(s)
+ a
NG
1
)
R
F
)
R
I
NG
Z(s)
This is written in a loop-gain analysis format, where the
errors arising from a non-infinite open-loop gain are shown
in the denominator. If Z(s) were infinite over all frequen-
cies, the denominator of Equation 14 reduces to 1 and the
ideal desired signal gain shown in the numerator is
achieved. The fraction in the denominator of Equation 14
determines the frequency response. Equation 15 shows
this as the loop-gain equation:
Z(s)
R
F
)
R
I
NG
+
LoopGain
If 20 log(R
F
+ NG
R
I
) is drawn on top of the open-loop
transimpedance plot, the difference between the two
would be the loop gain at a given frequency. Eventually,
Z(s) rolls off to equal the denominator of Equation 15, at
which point the loop gain has reduced to 1 (and the curves
have intersected). This point of equality is where the
amplifier closed-loop frequency response given by
Equation 14 starts to roll off, and is exactly analogous to
the frequency at which the noise gain equals the open-loop
voltage gain for a voltage-feedback op amp. The
difference here is that the total impedance in the
denominator of Equation 15 may be controlled somewhat
separately from the desired signal gain (or NG). The
OPA2674 is internally compensated to give a maximally
flat frequency response for R
F
= 402
at NG = 4 on
6V
(14)
(15)
OPA2674
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21
supplies. Evaluating the denominator of Equation 15
(which is the feedback transimpedance) gives an optimal
target of 490
. As the signal gain changes, the
contribution of the NG
R
I
term in the feedback
transimpedance changes, but the total can be held
constant by adjusting R
F
. Equation 16 gives an
approximate equation for optimum R
F
over signal gain:
R
F
+
490
*
NG
R
I
As the desired signal gain increases, this equation
eventually suggests a negative R
F
. A somewhat subjective
limit to this adjustment can also be set by holding R
G
to a
minimum value of 20
. Lower values load both the buffer
stage at the input and the output stage if R
F
gets too
low
actually decreasing the bandwidth. Figure 11 shows
the recommended R
F
versus NG for both
6V and a single
+5V operation. The values for R
F
versus gain shown here
are approximately equal to the values used to generate the
Typical Characteristics. They differ in that the optimized
values used in the Typical Characteristics are also
correcting for board parasitic not considered in the
simplified analysis leading to Equation 16. The values
shown in Figure 11 give a good starting point for designs
where bandwidth optimization is desired.
600
500
400
300
200
Noise Gain
0
25
10
15
20
5
F
eedb
ac
k
R
e
s
i
s
to
r
(
)
+5V
R
G
= 20
6V
Figure 11. Feedback Resistor vs Noise Gain
The total impedance going into the inverting input may be
used to adjust the closed-loop signal bandwidth. Inserting
a series resistor between the inverting input and the
summing junction increases the feedback impedance (the
denominator of Equation 15), decreasing the bandwidth.
The internal buffer output impedance for the OPA2674 is
slightly influenced by the source impedance coming from
of the noninverting input terminal. High-source resistors
also have the effect of increasing R
I
, decreasing the
bandwidth. For those single-supply applications that
develop a midpoint bias at the noninverting input through
high valued resistors, the decoupling capacitor is essential
for power-supply ripple rejection, noninverting input noise
current shunting, and to minimize the high-frequency
value for R
I
in Figure 10.
INVERTING AMPLIFIER OPERATION
As the OPA2674 is a general-purpose, wideband
current-feedback op amp, most of the familiar op amp
application circuits are available to the designer. Those
dual op amp applications that require considerable
flexibility in the feedback element (for example,
integrators, transimpedance, and some filters) should
consider a unity-gain stable, voltage-feedback amplifier
such as the OPA2822, because the feedback resistor is
the compensation element for a current-feedback op amp.
Wideband inverting operation (and especially summing) is
particularly suited to the OPA2674. Figure 12 shows a
typical inverting configuration where the I/O impedances
and signal gain from Figure 1 are retained in an inverting
circuit configuration.
1 /2
O P A 2 6 7 4
R
F
392
R
G
97.6
+6V
-
6V
50
50
Load
V
O
Power-supply
decoupling not
shown.
V
I
50
Source
R
M
102
Figure 12. Inverting Gain of -4 with Impedance
Matching
In the inverting configuration, two key design
considerations must be noted. First, the gain resistor (R
G
)
becomes part of the signal source input impedance. If
input impedance matching is desired (which is beneficial
whenever the signal is coupled through a cable, twisted
pair, long PC board trace, or other transmission line
conductor), it is normally necessary to add an additional
matching resistor to ground. R
G
, by itself, normally is not
set to the required input impedance since its value, along
with the desired gain, will determine an R
F
, which may be
nonoptimal from a frequency response standpoint. The
total input impedance for the source becomes the parallel
combination of R
G
and R
M
.
The second major consideration is that the signal source
impedance becomes part of the noise gain equation and
has a slight effect on the bandwidth through Equation 15.
The values shown in Figure 12 have accounted for this by
slightly decreasing R
F
(from the optimum values) to
reoptimize the bandwidth for the noise gain of Figure 12
(NG = 3.98). In the example of Figure 12, the R
M
value
combines in parallel with the external 50
source
impedance, yielding an effective driving impedance of
50
|| 102
= 33.5
. This impedance is added in series
(16)
OPA2674
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22
with R
G
for calculating the noise gain
which gives
NG = 3.98. This value, and the inverting input impedance
of 22
, are inserted into Equation 16 to get the R
F
that
appears in Figure 12. Note that the noninverting input in
this bipolar supply inverting application is connected
directly to ground.
It is often suggested that an additional resistor be
connected to ground on the noninverting input to achieve
bias current error cancellation at the output. The input bias
currents for a current-feedback op amp are not generally
matched in either magnitude or polarity. Connecting a
resistor to ground on the noninverting input of the
OPA2674 in the circuit of Figure 12 actually provides
additional gain for that input bias and noise currents, but
does not decrease the output DC error because the input
bias currents are not matched.
OUTPUT CURRENT AND VOLTAGE
The OPA2674 provides output voltage and current
capabilities that are unsurpassed in a low-cost dual
monolithic op amp. Under no-load conditions at 25
C, the
output voltage typically swings closer than 1V to either
supply rail; the tested (+25
C) swing limit is within 1.1V of
either rail. Into a 6
load (the minimum tested load), it
delivers more than
380mA.
The specifications described previously, though familiar in
the industry, consider voltage and current limits separately.
In many applications, it is the voltage times current (or V-I
product) that is more relevant to circuit operation. Refer to
the Output Voltage and Current Limitations plot in the
Typical Characteristics (see page 9). The X and Y axes of
this graph show the zero-voltage output current limit and
the zero-current output voltage limit, respectively. The four
quadrants give a more detailed view of the OPA2674
output drive capabilities, noting that the graph is bounded
by a safe operating area of 1W maximum internal power
dissipation (in this case, for one channel only).
Superimposing resistor load lines onto the plot shows that
the OPA2674 can drive
4V into 10
or
4.5V into 25
without exceeding the output capabilities or the 1W
dissipation limit. A 100
load line (the standard test circuit
load) shows the full
5.0V output swing capability, as
stated in the Electrical Characteristics tables. The
minimum specified output voltage and current over
temperature are set by worst-case simulations at the cold
temperature extreme. Only at cold startup will the output
current and voltage decrease to the numbers shown in the
Electrical Characteristics tables. As the output transistors
deliver power, the junction temperatures increase,
decreasing the V
BE
's (increasing the available output
voltage swing), and increasing the current gains
(increasing the available output current). In steady-state
operation, the available output voltage and current will
always be greater than that shown in the over-temperature
specifications since the output stage junction
temperatures will be higher than the minimum specified
operating ambient.
DRIVING CAPACITIVE LOADS
One of the most demanding and yet very common load
conditions for an op amp is capacitive loading. Often, the
capacitive load is the input of an analog-to-digital (A/D)
converter
including additional external capacitance that
may be recommended to improve the A/D converter
linearity. A high-speed, high open-loop gain amplifier like
the OPA2674 can be very susceptible to decreased
stability and closed-loop response peaking when a
capacitive load is placed directly on the output pin. When
the amplifier open-loop output resistance is considered,
this capacitive load introduces an additional pole in the
signal path that can decrease the phase margin. Several
external solutions to this problem have been suggested.
When the primary considerations are frequency response
flatness, pulse response fidelity, and/or distortion, the
simplest and most effective solution is to isolate the
capacitive load from the feedback loop by inserting a
series isolation resistor between the amplifier output and
the capacitive load. This does not eliminate the pole from
the loop response, but rather shifts it and adds a zero at a
higher frequency. The additional zero acts to cancel the
phase lag from the capacitive load pole, thus increasing
the phase margin and improving stability. The Typical
Characteristics show the Recommended R
S
vs Capacitive
Load and the resulting frequency response at the load.
Parasitic capacitive loads greater than 2pF can begin to
degrade the performance of the OPA2674. Long PC board
traces, unmatched cables, and connections to multiple
devices can easily cause this value to be exceeded.
Always consider this effect carefully, and add the
recommended series resistor as close as possible to the
OPA2674 output pin (see the Board Layout Guidelines
section).
DISTORTION PERFORMANCE
The OPA2674 provides good distortion performance into
a 100
load on
6V supplies. It also provides exceptional
performance into lighter loads and/or operating on a single
+5V supply. Generally, until the fundamental signal
reaches very high frequency or power levels, the
2nd-harmonic dominates the distortion with a negligible
3rd-harmonic component. Focusing then on the
2nd-harmonic, increasing the load impedance improves
distortion directly. Remember that the total load includes
the feedback network
in the noninverting configuration
(see Figure 1), this is the sum of R
F
+ R
G
; in the inverting
configuration, it is R
F
. Also, providing an additional supply
decoupling capacitor (0.01
F) between the supply pins
(for bipolar operation) improves the 2nd-order distortion
slightly (3dB to 6dB).
OPA2674
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23
In most op amps, increasing the output voltage swing
directly increases harmonic distortion. The Typical
Characteristics show the 2nd-harmonic increasing at a
little less than the expected 2x rate, whereas the
3rd-harmonic increases at a little less than the expected 3x
rate. Where the test power doubles, the difference
between it and the 2nd-harmonic decreases less than the
expected 6dB, whereas the difference between it and the
3rd-harmonic decreases by less than the expected 12dB.
This factor also shows up in the 2-tone, 3rd-order
intermodulation spurious (IM3) response curves. The
3rd-order spurious levels are extremely low at low-output
power levels. The output stage continues to hold them low
even as the fundamental power reaches very high levels.
As the Typical Characteristics show, the spurious
intermodulation powers do not increase as predicted by a
traditional intercept model. As the fundamental power
level increases, the dynamic range does not decrease
significantly. For two tones centered at 20MHz, with
10dBm/tone into a matched 50
load (i.e., 2V
PP
for each
tone at the load, which requires 8V
PP
for the overall 2-tone
envelope at the output pin), the Typical Characteristics
show 67dBc difference between the test-tone power and
the 3rd-order intermodulation spurious levels. This
exceptional performance improves further when operating
at lower frequencies.
NOISE PERFORMANCE
Wideband current-feedback op amps generally have a
higher output noise than comparable voltage-feedback op
amps. The OPA2674 offers an excellent balance between
voltage and current noise terms to achieve low output
noise. The inverting current noise (24pA/
Hz) is lower than
earlier solutions whereas the input voltage noise
(2.0nV/
Hz) is lower than most unity-gain stable,
wideband voltage-feedback op amps. This low input
voltage noise is achieved at the price of higher
noninverting input current noise (16pA/
Hz). As long as
the AC source impedance from the noninverting node is
less than 100
, this current noise does not contribute
significantly to the total output noise. The op amp input
voltage noise and the two input current noise terms
combine to give low output noise under a wide variety of
operating conditions. Figure 13 shows the op amp noise
analysis model with all noise terms included. In this model,
all noise terms are taken to be noise voltage or current
density terms in either nV/
Hz or pA/
Hz.
The total output spot noise voltage can be computed as the
square root of the sum of all squared output noise voltage
contributors. Equation 17 shows the general form for the
output noise voltage using the terms given in Figure 13.
E
O
+
ENI
2
)
IBN
R
S
2
)
4kTR
S
)
IBI
RF
2
)
4kTRFNG
4kT
R
G
R
G
R
F
R
S
1/2
OPA2674
I
BI
E
O
I
BN
4kT = 1.6E
-
20J
at 290
_
K
E
RS
E
NI
4
kTR
S
4kTR
F
Figure 13. Op Amp Noise Analysis Model
Dividing this expression by the noise gain (NG = (1 + R
F
/R
G
))
gives the equivalent input referred spot noise voltage at the
noninverting input, as shown in Equation 18.
E
N
+
E
NI
2
)
I
BN
R
S
2
)
4kTR
S
)
I
BI
R
F
NG
2
)
4kTR
F
NG
Evaluating these two equations for the OPA2674 circuit
and component values of Figure 1 gives a total output spot
noise voltage of 14.3nV/
Hz and a total equivalent input
spot noise voltage of 3.6nV/
Hz. This total input referred
spot noise voltage is higher than the 2.0nV/
Hz
specification for the op amp voltage noise alone. This
reflects the noise added to the output by the inverting
current noise times the feedback resistor. If the feedback
resistor is reduced in high-gain configurations (as
suggested previously), the total input referred voltage
noise given by Equation 18 approaches just the 2.0nV/
Hz
of the op amp. For example, going to a gain of +10 using
R
F
= 298
gives a total input referred noise of 2.3nV/
Hz.
DIFFERENTIAL NOISE PERFORMANCE
As the OPA2674 is used as a differential driver in xDSL
applications, it is important to analyze the noise in such a
configuration. See Figure 14 for the op amp noise model
for the differential configuration.
(17)
(18)
OPA2674
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24
R
G
R
F
R
S
E
O
2
Driver
E
RS
E
N
I
N
I
I
4
kTR
S
4kTR
F
R
F
R
S
E
RS
E
N
I
N
I
I
4
kTR
S
4kTR
G
4kTR
F
Figure 14. Differential Op Amp Noise Analysis
Model
As a reminder, the differential gain is expressed as:
G
D
+
1
)
2
R
F
R
G
The output noise voltage can be expressed as shown below:
e
O
2
+
2
G
D
2
e
N
2
)
i
N
R
S
2
)
4kTR
S
)
2 i
I
R
F
2
)
2 4kTR
F
G
D
Dividing this expression by the differential noise gain
G
D
= (1 + 2R
F
/R
G
) gives the equivalent input referred
spot noise voltage at the noninverting input, as shown in
Equation 21.
e
N
+
2
e
N
2
)
i
N
R
S
2
)
4kTR
S
)
2 i
I
R
F
G
D
2
)
2
4kTR
F
G
D
Evaluating this equation for the OPA2674 circuit and
component values of Figure 5 gives a total output spot
noise voltage of 31.0nV/
Hz and a total equivalent input
spot noise voltage of 3.5nV/
Hz.
In order to minimize the noise contributed by I
N
, it is
recommended to keep the noninverting source impedance
as low as possible.
DC ACCURACY AND OFFSET CONTROL
A current-feedback op amp such as the OPA2674
provides exceptional bandwidth in high gains, giving fast
pulse settling but only moderate DC accuracy. The
Electrical Characteristics show an input offset voltage
comparable to high-speed, voltage-feedback amplifiers;
however, the two input bias currents are somewhat higher
and are unmatched. While bias current cancellation
techniques are very effective with most voltage-feedback
op amps, they do not generally reduce the output DC offset
for wideband current-feedback op amps. Because the two
input bias currents are unrelated in both magnitude and
polarity, matching the input source impedance to reduce
error contribution to the output is ineffective. Evaluating
the configuration of Figure 1, using worst-case +25
C
input offset voltage and the two input bias currents, gives
a worst-case output offset range equal to:
V
OS
=
(NG
V
IO(MAX)
)
(I
BN
R
S
/2
NG)
(I
BI
R
F
)
where NG = noninverting signal gain
=
(4
4.5mV)
(30
A
25
4)
(402
35
A)
=
18mV
3mV
14mV
V
OS
=
35.0mV (max at 25
C)
POWER CONTROL OPERATION (SO-14 ONLY)
The OPA2674I-14D provides a power control feature that
may be used to reduce system power. The four modes of
operation for this power control feature are full-power,
power cutback, idle state, and power shutdown. These
four operating modes are set through two logic lines A0
and A1. Table 3 shows the different modes of operation.
Table 3. Power Control Mode of Operation
MODE OF
OPERATION
A1
A0
Full
-
Power
1
1
Power Cutback
1
0
Idle State
0
1
Shutdown
0
0
The full-power mode is used for normal operating
condition. The power cutback mode brings the quiescent
power to 13.5mA. The idle state mode keeps a low output
impedance but reduces output power and bandwidth. The
shutdown mode has a high output impedance as well as
the lowest quiescent power (1.0mA).
If the A0 and A1 pins are left unconnected, the
OPA2674I-14D operates normally (full-power).
(19)
(20)
(21)
OPA2674
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25
To change the power mode, the control pins (either A0 or
A1) must be asserted low. This logic control is referenced
to the positive supply, as shown in the simplified circuit of
Figure 15.
46k
60k
1.2V
120k
Control
-
V
S
+V
S
A0 or A1
-
V
S
Q1
Q2
Figure 15. Supply Power Control Circuit
The shutdown feature for the OPA2674 is a positive-sup-
ply referenced, current-controlled interface. Open-collec-
tor (or drain) interfaces are most effective, as long as the
controlling logic can sustain the resulting voltage (in open
mode) that appears at the A0 or A1 pins. The A0/A1 pin
voltage is one diode below the positive supply voltage
applied to the OPA2674 if the logic interface is open. For
voltage output logic interfaces, the on/off voltage levels
described in the Electrical Characteristics apply only for
either the +6V used for the
6V specifications or the +5V
for the single-supply specifications. An open-drain
interface is recommended to operate the A1 and A0 pins
using a higher positive supply and/or logic families with
inadequate high-level voltage swings.
THERMAL ANALYSIS
Due to the high output power capability of the OPA2674,
heat-sinking or forced airflow may be required under extreme
operating conditions. Maximum desired junction temperature
sets the maximum allowed internal power dissipation,
described below. In no case should the maximum junction
temperature be allowed to exceed 150
C.
Operating junction temperature (T
J
) is given by T
A
+ P
D
q
JA
. The total internal power dissipation (P
D
) is the sum of
quiescent power (P
DQ
) and additional power dissipation in
the output stage (P
DL
) to deliver load power. Quiescent
power is the specified no-load supply current times the
total supply voltage across the part. P
DL
depends on the
required output signal and load. Using the example power
calculation for the ADSL CPE line driver concluded in
Equation 13, and a worst-case analysis at +70
C ambient,
the maximum internal junction temperature for the SO-8
package will be:
T
J MAX
= T
AMBIENT
+ P
MAX
125
C/W
T
J MAX
= 70
C + ((12V
18.8mA) + 12V
128mA/(5.33)
- 40mW)
125
C/W = 129
C
This maximum junction temperature is well below the
maximum of 150
C but may exceed system design
targets. Lower junction temperature would be possible
using the SO-14 package and the power cutback feature.
Repeating this calculation for that solution gives:
T
J MAX
= 70
C + ((12V
14.2mA) + 12V
128mA/(5.33)
- 40mW)
100
C/W = 112
C
For extremely high internal power applications, where
improved thermal performance is required, consider the
PSO-8 package of the OPA2677--a similar part with no
output stage current limit and a thermal impedance of less
than 50
C/W.
BOARD LAYOUT GUIDELINES
Achieving optimum performance with a high-frequency
amplifier like the OPA2674 requires careful attention to
board layout parasitic and external component types.
Recommendations that optimize performance include:
a) Minimize parasitic capacitance to any AC ground for
all of the signal I/O pins. Parasitic capacitance on the
output and inverting input pins can cause instability; on the
noninverting input, it can react with the source impedance
to cause unintentional band limiting. To reduce unwanted
capacitance, a window around the signal I/O pins should
be opened in all of the ground and power planes around
those pins. Otherwise, ground and power planes should
be unbroken elsewhere on the board.
b) Minimize the distance (< 0.25
) from the power-supply
pins to high-frequency 0.1
F decoupling capacitors. At the
device pins, the ground and power plane layout should not
be in close proximity to the signal I/O pins. Avoid narrow
power and ground traces to minimize inductance between
the pins and the decoupling capacitors. The power-supply
connections (on pins 4 and 8 for an SO-8 package) should
always be decoupled with these capacitors. An optional
supply decoupling capacitor across the two power supplies
(for bipolar operation) improves 2nd-harmonic distortion
performance. Larger (2.2
F to 6.8
F) decoupling
capacitors, effective at a lower frequency, should also be
used on the main supply pins. These can be placed
somewhat farther from the device and may be shared
among several devices in the same area of the PC board.
c) Careful selection and placement of external
components preserve the high-frequency performance
of the OPA2674.
Resistors should be of a very low
reactance type. Surface-mount resistors work best and
allow a tighter overall layout. Metal film and carbon
composition axially leaded resistors can also provide good
high-frequency performance. Again, keep the leads and
PC board trace length as short as possible. Never use
wire-wound type resistors in a high-frequency application.
Although the output pin and inverting input pin are the most
OPA2674
SBOS270 - AUGUST 2003
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26
sensitive to parasitic capacitance, always position the
feedback and series output resistor, if any, as close as
possible to the output pin. Other network components,
such as noninverting input termination resistors, should
also be placed close to the package. Where double-side
component mounting is allowed, place the feedback
resistor directly under the package on the other side of the
board between the output and inverting input pins. The
frequency response is primarily determined by the
feedback resistor value as described previously.
Increasing the value reduces the bandwidth, whereas
decreasing it gives a more peaked frequency response.
The 402
feedback resistor used in the Typical
Characteristics at a gain of +4 on
6V supplies is a good
starting point for design. Note that a 511
feedback
resistor, rather than a direct short, is recommended for the
unity-gain follower application. A current-feedback op amp
requires a feedback resistor even in the unity-gain follower
configuration to control stability.
d) Connections to other wideband devices on the board
may be made with short direct traces or through onboard
transmission lines. For short connections, consider the
trace and the input to the next device as a lumped
capacitive load. Relatively wide traces (50mils to 100mils)
should be used, preferably with ground and power planes
opened up around them. Estimate the total capacitive load
and set R
S
from the plot of Recommended R
S
vs
Capacitive Load (see page 10). Low parasitic capacitive
loads (< 5pF) may not need an R
S
because the OPA2674
is nominally compensated to operate with a 2pF parasitic
load. If a long trace is required, and the 6dB signal loss
intrinsic to a doubly-terminated transmission line is
acceptable, implement a matched impedance transmis-
sion line using microstrip or stripline techniques (consult
an ECL design handbook for microstrip and stripline layout
techniques). A 50
environment is normally not necessary
onboard. In fact, a higher impedance environment
improves distortion; see the distortion versus load plots.
With a characteristic board trace impedance defined
based on board material and trace dimensions, a matching
series resistor into the trace from the output of the
OPA2674 is used, as well as a terminating shunt resistor
at the input of the destination device. Remember also that
the terminating impedance is the parallel combination of
the shunt resistor and the input impedance of the
destination device.
This total effective impedance should be set to match the
trace impedance. The high output voltage and current
capability of the OPA2674 allows multiple destination
devices to be handled as separate transmission lines,
each with their own series and shunt terminations. If the
6dB attenuation of a doubly-terminated transmission line
is unacceptable, a long trace can be series-terminated at
the source end only. Treat the trace as a capacitive load in
this case, and set the series resistor value as shown in the
plot of R
S
vs Capacitive Load. However, this does not
preserve signal integrity as well as a doubly-terminated
line. If the input impedance of the destination device is low,
there is some signal attenuation due to the voltage divider
formed by the series output into the terminating
impedance.
e) Socketing a high-speed part like the OPA2674 is not
recommended.
The additional lead length and pin-to-pin
capacitance introduced by the socket can create an
extremely troublesome parasitic network, which can make
it almost impossible to achieve a smooth, stable frequency
response. Best results are obtained by soldering the
OPA2674 onto the board.
INPUT AND ESD PROTECTION
The OPA2674 is built using a high-speed complementary
bipolar process. The internal junction breakdown voltages
are relatively low for these very small geometry devices
and are reflected in the absolute maximum ratings table.
All device pins have limited ESD protection using internal
diodes to the power supplies, as shown in Figure 16.
These diodes provide moderate protection to input
overdrive voltages above the supplies as well. The
protection diodes can typically support 30mA continuous
current. Where higher currents are possible (for example,
in systems with
15V supply parts driving into the
OPA2674), current-limiting series resistors should be
added into the two inputs. Keep these resistor values as
low as possible, because high values degrade both noise
performance and frequency response.
External
Pin
+V
CC
-
V
CC
Internal
Circuitry
Figure 16. ESD Steering Diodes
PACKAGING INFORMATION
Orderable Device
Status
(1)
Package
Type
Package
Drawing
Pins Package
Qty
Eco Plan
(2)
Lead/Ball Finish
MSL Peak Temp
(3)
OPA2674I-14D
ACTIVE
SOIC
D
14
58
None
CU SNPB
Level-3-220C-168 HR
OPA2674I-14DR
ACTIVE
SOIC
D
14
2500
None
CU SNPB
Level-3-220C-168 HR
OPA2674ID
ACTIVE
SOIC
D
8
100
None
CU SNPB
Level-3-235C-168 HR
OPA2674IDR
ACTIVE
SOIC
D
8
2500
None
CU SNPB
Level-3-235C-168 HR
(1)
The marketing status values are defined as follows:
ACTIVE: Product device recommended for new designs.
LIFEBUY: TI has announced that the device will be discontinued, and a lifetime-buy period is in effect.
NRND: Not recommended for new designs. Device is in production to support existing customers, but TI does not recommend using this part in
a new design.
PREVIEW: Device has been announced but is not in production. Samples may or may not be available.
OBSOLETE: TI has discontinued the production of the device.
(2)
Eco Plan - May not be currently available - please check
http://www.ti.com/productcontent
for the latest availability information and additional
product content details.
None: Not yet available Lead (Pb-Free).
Pb-Free (RoHS): TI's terms "Lead-Free" or "Pb-Free" mean semiconductor products that are compatible with the current RoHS requirements
for all 6 substances, including the requirement that lead not exceed 0.1% by weight in homogeneous materials. Where designed to be soldered
at high temperatures, TI Pb-Free products are suitable for use in specified lead-free processes.
Green (RoHS & no Sb/Br): TI defines "Green" to mean "Pb-Free" and in addition, uses package materials that do not contain halogens,
including bromine (Br) or antimony (Sb) above 0.1% of total product weight.
(3)
MSL, Peak Temp. -- The Moisture Sensitivity Level rating according to the JEDECindustry standard classifications, and peak solder
temperature.
Important Information and Disclaimer:The information provided on this page represents TI's knowledge and belief as of the date that it is
provided. TI bases its knowledge and belief on information provided by third parties, and makes no representation or warranty as to the
accuracy of such information. Efforts are underway to better integrate information from third parties. TI has taken and continues to take
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incoming materials and chemicals. TI and TI suppliers consider certain information to be proprietary, and thus CAS numbers and other limited
information may not be available for release.
In no event shall TI's liability arising out of such information exceed the total purchase price of the TI part(s) at issue in this document sold by TI
to Customer on an annual basis.
PACKAGE OPTION ADDENDUM
www.ti.com
9-Dec-2004
Addendum-Page 1
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