Document Outline
- FEATURES
- APPLICATIONS
- DESCRIPTION
- OPA725 RELATED PRODUCTS
- ORDERING INFORMATION
- ABSOLUTE MAXIMUM RATINGS(
- PIN CONFIGURATIONS
- ELECTRICAL CHARACTERISTICS: VS = +4V to +12V or VS = 2V to 6V
- TYPICAL CHARACTERISTICS
- APPLICATIONS INFORMATION
- OPERATING VOLTAGE
- ENABLE/SHUTDOWN
- COMMON-MODE VOLTAGE RANGE
- INPUT OVER-VOLTAGE PROTECTION
- RAIL-TO-RAIL OUTPUT
- CAPACITIVE LOAD AND STABILITY
- DRIVING FAST 16-BIT ADCs
- TRANSIMPEDANCE AMPLIFIER
- OPTIMIZING THE TRANSIMPEDANCE CIRCUIT
FEATURES
D
BANDWIDTH: 20MHz
D
SLEW RATE: 30V/
s
D
FAST 16-BIT SETTLING TIME
D
LOW NOISE: 6nV/
Hz (typ) at 100kHz
D
EXCELLENT CMRR, PSRR, and A
OL
D
RAIL-TO-RAIL OUTPUT
D
CM RANGE INCLUDES GND
D
THD+N: 0.0003% (typ) at 1kHz
D
QUIESCENT CURRENT: 5.5mA/ch (max)
D
SUPPLY VOLTAGE: 4V to 12V
D
SHUTDOWN MODE (OPAx726): 6
A/ch
APPLICATIONS
D
OPTICAL NETWORKING
D
TRANSIMPEDANCE AMPLIFIERS
D
INTEGRATORS
D
ACTIVE FILTERS
D
A/D CONVERTER BUFFERS
D
I/V CONVERTER FOR DACs
D
PORTABLE AUDIO
D
PROCESS CONTROL
D
TEST EQUIPMENT
OPA725 RELATED PRODUCTS
FEATURES
PRODUCT
10MHz, 16V, 16V/
s, 8.5nV/
Hz at 1kHz
TLC080
8MHz, 36V, FET Input, 20V/
s, 8.5nV/
Hz at 1kHz
OPA132
100MHz, 5.5V, Precision Transimpedance Amplifier
OPA380
500MHz,
5V, FET Input, 290V/
s, 7nV/
Hz at 100kHz
OPA656
7MHz, 12V, RRIO, 10V/
s, 30nV/
Hz at 10kHz
OPA743
16-Bit, 250kSPS, 4-Channel, Parallel Output ADC
ADS8342
DESCRIPTION
The OPA725 and OPA726 series op amps use a
state-of-the-art 12V analog CMOS process, and combine
outstanding ac performance with low bias current and
excellent CMRR, PSRR, and A
OL
. The 20MHz
Gain-Bandwidth (GBW) Product is achieved by using a
proprietary and patent-pending output stage design.
These characteristics allow excellent 16-bit settling times
for driving 16-bit Analog-to-Digital converters (ADCs).
Excellent ac characteristics, such as 20MHz GBW, 30V/
s
slew rate and 0.0003% THD+N make the OPA725 and
OPA726 well-suited for communication, high-end audio,
and active filter applications. With a bias current of less
than 200pA, they are well-suited for use as
transimpedance (I/V-conversion) amplifiers for monitoring
optical power in ONET applications.
The OPA725 and OPA726 op amps can be used in
single-supply applications from 4V up to 12V, or
dual-supply from
2V to
6V. The output swings to within
150mV of the rails, maximizing dynamic range. The
shutdown versions (OPAx726) reduce the quiescent
current to less than 6
A and feature a reference pin for
easy shutdown operation with standard CMOS logic in
dual-supply applications.
The OPA725 (single) is available in SOT23-5 and SO-8
packages, and the OPA2725 (dual) is available in MSOP-8
and SO-8 packages. The OPA726 (single with shutdown)
is available in MSOP-8 and SO-8. The OPA2726 (dual with
shutdown) is available in MSOP-10. All versions are
specified for operation from -40
C to +125
C.
-
V
B
V
OUT
+12V
Enable
O PA 726
75
OPA725
ADS8342
16-Bit ADC
AIN
Common
330pF
V
IN
2.5V
+5V
-
5V
+5V
-
5V
OPA725, OPA2725
OPA726, OPA2726
SBOS278B - SEPTEMBER 2003 - REVISED JANUARY 2004
Very Low Noise, High-Speed, 12V CMOS
Operational Amplifier
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.
www.ti.com
Copyright
2003-2004, 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.
OPA725, OPA2725
OPA726, OPA2726
SBOS278B - SEPTEMBER 2003 - REVISED JANUARY 2004
www.ti.com
2
ORDERING INFORMATION
PRODUCT
PACKAGE-LEAD
PACKAGE
DESIGNATOR(1)
SPECIFIED
TEMPERATURE
RANGE
PACKAGE
MARKING
ORDERING
NUMBER
TRANSPORT
MEDIA, QUANTITY
Non-Shutdown
OPA725
SOT23-5
DBV
-40
C to +125
C
OALI
OPA725AIDBVT
Tape and Reel, 250
OPA725AIDBVR
Tape and Reel, 3000
OPA725
SO-8
D
-40
C to +125
C
OPA725A
OPA725AID
Rails, 100
OPA725AIDR
Tape and Reel, 2500
OPA2725
SO-8
D
-40
C to +125
C
OPA2725A
OPA2725AID
Rails, 100
OPA2725AIDR
Tape and Reel, 2500
OPA2725
MSOP-8
DGK
-40
C to +125
C
BGM
OPA2725AIDGKT
Tape and Reel, 250
OPA2725AIDGKR
Tape and Reel, 2500
Shutdown
OPA726
SO-8
D
-40
C to +125
C
OPA726A
OPA726AID
Rails, 100
OPA726AIDR
Tape and Reel, 2500
OPA726
MSOP-8
DGK
-40
C to +125
C
BHC
OPA726AIDGKT
Tape and Reel, 250
OPA726AIDGKR
Tape and Reel, 2500
OPA2726
MSOP-10
DGS
-40
C to +125
C
BHB
OPA2726AIDGST
Tape and Reel, 250
OPA2726AIDGSR
Tape and Reel, 2500
(1) For the most current package and ordering information, see the Package Option Addendum located at the end of this datasheet.
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.
ABSOLUTE MAXIMUM RATINGS
(1)
Supply Voltage
+13.2V
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Signal Input Terminals, Voltage(2)
-0.5V to (V+) + 0.5V
. . . . . . . . .
Current(2)
10mA
. . . . . . . . . . . . . . . . . . .
Output Short Circuit(3) Continuous
. . . . . . . . . . . . . . . . . . . . . . . . .
Operating Temperature
-55
C to +125
C
. . . . . . . . . . . . . . . . . . . . .
Storage Termperature
-55
C to +150
C
. . . . . . . . . . . . . . . . . . . . . .
Junction Temperature
+150
C
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Lead Temperature (soldering, 10s)
+300
C
. . . . . . . . . . . . . . . . . . . .
ESD Rating (Human Body Model)
1000 V
. . . . . . . . . . . . . . . . . . . .
(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) Input terminals are diode-clamped to the power-supply rails.
Input signals that can swing more than 0.5V beyond the supply
rails should be current limited to 10mA or less.
(3) Short-circuit to ground, one amplifier per package.
OPA725, OPA2725
OPA726, OPA2726
SBOS278B - SEPTEMBER 2003 - REVISED JANUARY 2004
www.ti.com
3
PIN CONFIGURATIONS
(1) NC denotes no internal connection.
(2) DGND = reference voltage for Enable Reference pin. Voltage on this pin
will be the voltage to which the Enable Reference pin is referenced.
1
2
3
5
4
V+
-
IN
Out
V
-
+IN
OPA725
SOT23-5
1
2
3
4
8
7
6
5
NC
(1)
V+
OUT
NC
(1)
NC
(1)
-
IN
+IN
V
-
OPA725
SO-8
1
2
3
4
8
7
6
5
V+
OUT B
-
IN B
+IN B
OUT A
-
IN A
+IN A
V
-
OPA2725
SO-8, MSOP-8
A
B
1
2
3
4
8
7
6
5
Enable
V+
OUT
NC
(1)
DGND
(2)
-
IN
+IN
V
-
OPA726
SO-8, MSOP-8
1
2
3
4
5
10
9
8
7
6
V+
OUT B
-
IN B
+IN B
Enable
OUT A
-
IN A
+IN A
V
-
DGND
(2)
OPA2726
MSOP-10
A
B
OPA725, OPA2725
OPA726, OPA2726
SBOS278B - SEPTEMBER 2003 - REVISED JANUARY 2004
www.ti.com
4
ELECTRICAL CHARACTERISTICS: V
S
= +4V to +12V or V
S
=
2V to
6V
Boldface limits apply over the specified temperature range, T
A
= -40
C to +125
C.
At TA = +25
C, RL = 10k
connected to VS/2, and VOUT = VS/2, unless otherwise noted.
OPA725, OPA726, OPA2725, OPA2726
PARAMETER
CONDITIONS
MIN
TYP
MAX
UNIT
OFFSET VOLTAGE
Input Offset Voltage
V
OS
OPA725, OPA726
V
S
=
6V, V
CM
= 0V
1.2
3
mV
OPA2725, OPA2726
V
S
=
6V, V
CM
= 0V
1.5
5
mV
Drift dV
OS
/dT
4
V/
C
vs Power Supply
PSRR
V
S
=
2V to
6V, V
CM
= V-
30
100
V/V
Over Temperature
V
S
=
2V to
6V, V
CM
= V-
150
m
V/V
Channel Separation, DC
1
V/V
INPUT BIAS CURRENT
Input Bias Current
I
B
30
200
pA
Over Temperature
See Typical Characteristics
Input Offset Current
I
OS
10
50
pA
NOISE
Input Voltage Noise, f = 0.1Hz to 10Hz
e
n
V
S
=
6V, V
CM
= 0V
10
V
PP
Input Voltage Noise Density, f = 10kHz
e
n
V
S
=
6V, V
CM
= 0V
10
nV/
Hz
Input Voltage Noise Density, f = 100kHz
e
n
V
S
=
6V, V
CM
= 0V
6
nV/
Hz
Input Current Noise Density, f = 1kHz
i
n
V
S
=
6V, V
CM
= 0V
2.5
fA/
Hz
INPUT VOLTAGE RANGE
Common-Mode Voltage Range
V
CM
(V-)
(V+) - 2
V
Common-Mode Rejection Ratio
CMRR
(V-)
V
CM
(V+) - 2V
88
94
dB
Over Temperature
(V-)
V
CM
(V+) - 2V
84
dB
(V-)
V
CM
(V+) - 3V
94
100
dB
Over Temperature
(V-)
V
CM
(V+) - 3V
84
dB
INPUT IMPEDANCE
Differential
10
11
5
pF
Common-Mode
10
11
4
pF
OPEN-LOOP GAIN
Open-Loop Voltage Gain
A
OL
OPA725, OPA726
R
L
= 100k
, 0.15V < V
O
< (V+) - 0.15V
110
120
dB
Over Temperature
R
L
= 100k
, 0.15V < V
O
< (V+) - 0.15V
100
dB
OPA2725, OPA2726
R
L
= 100k
, 0.175V < V
O
< (V+) - 0.175V
110
120
dB
Over Temperature
R
L
= 100k
, 0.175V < V
O
< (V+) - 0.175V
100
dB
OPA725, OPA726
R
L
= 1k
, 0.25V < V
O
< (V+) - 0.25V
106
116
dB
Over Temperature
R
L
= 1k
, 0.25V < V
O
< (V+) - 0.25V
96
dB
OPA2725, OPA2726
R
L
= 2k
, 0.25V < V
O
< (V+) - 0.25V
106
116
dB
Over Temperature
R
L
= 2k
, 0.25V < V
O
< (V+) - 0.25V
96
dB
FREQUENCY RESPONSE
C
L
= 20pF
Gain-Bandwidth Product
GBW
20
MHz
Slew Rate
SR
G = +1
30
V/
s
Settling Time, 0.1%
t
S
V
S
=
6V, 5V Step, G = +1
350
ns
0.01%
V
S
=
6V, 5V Step, G = +1
450
ns
Overload Recovery Time
V
IN
Gain > V
S
50
ns
Total Harmonic Distortion + Noise
THD+N
VS =
6V, VOUT = 2VRMS, RL = 600
,
G = +1, f = 1kHz
0.0003
%
OPA725, OPA2725
OPA726, OPA2726
SBOS278B - SEPTEMBER 2003 - REVISED JANUARY 2004
www.ti.com
5
ELECTRICAL CHARACTERISTICS: V
S
= +4V to +12V or V
S
=
2V to
6V (continued)
Boldface limits apply over the specified temperature range, T
A
= -40
C to +125
C.
At TA = +25
C, RL = 10k
connected to VS/2, and VOUT = VS/2, unless otherwise noted.
OPA725, OPA726, OPA2725, OPA2726
PARAMETER
UNIT
MAX
TYP
MIN
CONDITIONS
OUTPUT
Voltage Output Swing from Rail
OPA725, OPA726
R
L
= 100k
, A
OL
> 110dB
100
150
mV
Over Temperature
R
L
= 100k
, A
OL
> 100dB
150
mV
OPA2725, OPA2726
R
L
= 100k
, A
OL
> 110dB
125
175
mV
Over Temperature
R
L
= 100k
, A
OL
> 100dB
175
mV
OPA725, OPA726
R
L
= 1k
, A
OL
> 106dB
200
250
mV
Over Temperature
R
L
= 1k
, A
OL
> 96dB
250
mV
OPA2725, OPA2726
R
L
= 2k
, A
OL
> 106dB
200
250
mV
Over Temperature
R
L
= 2k
, A
OL
> 96dB
250
mV
Output Current
I
OUT
V
S
- V
OUT
< 1V
40
mA
Short-Circuit Current
I
SC
55
mA
Capacitive Load Drive
C
LOAD
See Typical Characteristics
Open-Loop Output Impedance
f = 1MHz, I
O
= 0
40
ENABLE/SHUTDOWN (OPAx726)
t
OFF
5
s
t
ON
30
s
Enable Reference (DGND) Voltage Range V
DGND
V-
(V+) - 2
V
V
L
(shutdown)
< V
DGND
+0.8V
V
V
H
(amplifier is active)
> V
DGND
+2V
V
Input Disable Current
Ref Pin = Enable Pin = V-
5
A
I
QSD
(per amplifier)
6
15
A
POWER SUPPLY
Specified Voltage Range
V
S
4
12
V
Operating Voltage Range
V
S
3.5 to 13.2
V
Quiescent Current (per amplifier)
I
Q
I
O
= 0
4.3
5.5
mA
Over Temperature
6
mA
TEMPERATURE RANGE
Specified Range
-40
125
C
Operating Range
-55
125
C
Storage Range
-55
150
C
Thermal Resistance
q
JA
SOT23-5
200
C/W
MSOP-8, MSOP-10, SO-8
150
C/W
OPA725, OPA2725
OPA726, OPA2726
SBOS278B - SEPTEMBER 2003 - REVISED JANUARY 2004
www.ti.com
6
TYPICAL CHARACTERISTICS
At TA = +25
C, VS =
6V, RL = 10k
connected to VS/2, and VOUT = VS/2, unless otherwise noted.
GAIN AND PHASE vs FREQUENCY
Frequency (Hz)
10
100
1k
10k
100k
1M
10M
100M
180
160
140
120
100
80
60
40
20
0
-
20
180
160
140
120
100
80
60
40
20
0
-
20
Ga
i
n
(
d
B
)
Ph
a
s
e
(
_
)
Gain
Phase
POWER-SUPPLY REJECTION RATIO vs FREQUENCY
Frequency (Hz)
100
1k
10k
100k
1M
10M
100M
100
90
80
70
60
50
40
30
20
10
0
PS
R
R
(
d
B
)
CHANNEL SEPARATION vs FREQUENCY
Frequency (Hz)
1k
10k
100k
1M
10M
100M
140
120
100
80
60
40
20
C
h
ann
e
l
S
epa
r
a
ti
on
(
d
B
)
COMMON-MODE REJECTION RATIO vs FREQUENCY
Frequency (Hz)
10
100
1k
10k
100k
1M
10M
120
100
80
60
40
20
0
CM
RR
(
d
B
)
(V
-
)
V
CM
(V+)
-
2V
MAXIMUM OUTPUT VOLTAGE vs FREQUENCY
Frequency (Hz)
10k
100k
1M
10M
7
6
5
4
3
2
1
0
A
m
pl
i
t
ud
e
(
V
)
V
S
=
6V
Indicates maximum output
for no visible distortion.
INPUT VOLTAGE NOISE SPECTRAL DENSITY
vs FREQUENCY
Frequency (Hz)
10
100
1k
10k
100k
1M
10M
1000
100
10
1
V
o
l
t
ag
e
N
oi
s
e
(
n
V
/
Hz
)
OPA725, OPA2725
OPA726, OPA2726
SBOS278B - SEPTEMBER 2003 - REVISED JANUARY 2004
www.ti.com
7
TYPICAL CHARACTERISTICS (continued)
At TA = +25
C, VS =
6V, RL = 10k
connected to VS/2, and VOUT = VS/2, unless otherwise noted.
INPUT BIAS CURRENT vs COMMON-MODE VOLTAGE
Common-Mode Voltage (V)
-
6.5
-
5.5
-
4.5
-
3.5
-
2.5
-
1.5
-
0.5
0.
5
1.
5
2.
5
3.
5
4.
5
5.
5
6.
5
100k
10k
1k
100
10
-
10
-
100
-
1k
-
10k
-
100k
Inpu
t
B
i
a
s
C
ur
r
e
n
t
(
p
A
)
I
B
<
10pA
+125
_
C
+125
_
C
+85
_
C
+85
_
C
+25
_
C
+25
_
C
OPEN-LOOP GAIN vs TEMPERATURE
140
130
120
110
100
90
80
A
OL
(d
B
)
Temperature (
_
C)
-
50
-
25
0
25
50
75
100
125
150
R
L
= 1k
R
L
= 100k
COMMON-MODE REJECTION RATIO vs TEMPERATURE
110
100
90
80
70
60
CM
RR
(
d
B
)
Temperature (
_
C)
-
50
-
25
0
25
50
75
100
125
150
(V
-
)
V
CM
(V+)
-
2V
OFFSET CURRENT vs TEMPERATURE
10k
1k
100
10
1
0.1
0.01
I
OS
(p
A
)
Temperature (
_
C)
-
50
-
25
0
25
50
75
100
125
150
POWER-SUPPLY REJECTION RATIO vs TEMPERATURE
120
100
80
60
PS
R
R
(
d
B)
Temperature (
_
C)
-
50
-
25
0
25
50
75
100
125
150
QUIESCENT CURRENT vs TEMPERATURE
5
4
3
2
1
0
I
Q
(m
A
)
Temperature (
_
C)
-
50
-
25
0
25
50
75
100
125
150
OPA725, OPA2725
OPA726, OPA2726
SBOS278B - SEPTEMBER 2003 - REVISED JANUARY 2004
www.ti.com
8
TYPICAL CHARACTERISTICS (continued)
At TA = +25
C, VS =
6V, RL = 10k
connected to VS/2, and VOUT = VS/2, unless otherwise noted.
QUIESCENT CURRENT vs SUPPLY VOLTAGE
Supply Voltage (V)
3
4
5
6
7
8
9
10
11
12
13
14
5.0
4.8
4.6
4.4
4.2
4.0
3.8
3.6
3.4
3.2
3.0
I
Q
per
A
m
pl
i
f
i
e
r
(
m
A
)
SHORT-CIRCUIT CURRENT vs SUPPLY VOLTAGE
Supply Voltage (V)
3.
5
4.
5
5.
5
6.
5
7.
5
8.
5
9.
5
10
.5
11
.5
12
.5
13
.5
90
80
70
60
50
40
30
20
10
0
Sh
o
r
t
-
C
i
rc
u
i
t
C
u
r
re
n
t
(m
A
)
Sourcing
Sinking
TOTAL HARMONIC DISTORTION + NOISE vs FREQUENCY
Frequency (Hz)
10
100
1k
10k
100k
0.01
0.001
0.0001
TH
D
+
N
o
i
s
e
(
%)
R
L
= 600
V
OUT
= 2Vrms
BW = 80kHz
SHORT-CIRCUIT CURRENT vs TEMPERATURE
90
80
70
60
50
40
30
20
10
0
S
hor
t-
C
i
r
c
u
i
t
(
mA
)
Temperature (
_
C)
-
50
-
25
0
25
50
75
100
125
150
Sourcing
Sinking
OUTPUT VOLTAGE SWING vs OUTPUT CURRENT
Output Current (mA)
0
10
20
30
40
50
60
70
80
6
4
2
0
-
2
-
4
-
6
O
u
tp
ut
V
o
l
t
ag
e
(
V
)
125
_
C
-
40
_
C
-
40
_
C
25
_
C
SETTLING TIME vs GAIN
Noninverting Gain (V/V)
1
10
100
5000
4500
4000
3500
3000
2500
2000
1500
1000
500
0
0.01%
0.1%
Settling
T
ime (ns)
OPA725, OPA2725
OPA726, OPA2726
SBOS278B - SEPTEMBER 2003 - REVISED JANUARY 2004
www.ti.com
9
TYPICAL CHARACTERISTICS (continued)
At TA = +25
C, VS =
6V, RL = 10k
connected to VS/2, and VOUT = VS/2, unless otherwise noted.
SMALL-SIGNAL OVERSHOOT vs CAPACITIVE LOAD
Capacitive Load (pF)
10
100
1000
90
80
70
60
50
40
30
20
10
0
Ov
e
r
s
h
o
o
t
(
%
)
G = +1
G =
-
1
C
F
= 3pF
G = +5
C
F
= 1pF
VOLTAGE OFFSET DRIFT PRODUCTION DISTRIBUTION
Voltage Offset Drift (
V/
_
C)
2
0
4
6
8
10
12
14
16
P
o
pu
l
a
t
i
on
Typical production distribution
of packaged units.
LARGE-SIGNAL STEP RESPONSE
400ns/div
1V
/d
i
v
G = +1
R
L
= 10k
C
L
= 20pF
OFFSET VOLTAGE PRODUCTION DISTRIBUTION
Offset Voltage (mV)
-
3.3
-
3.0
-
2.7
-
2.4
-
2.1
-
1.8
-
1.5
-
1.2
-
0.9
-
0.6
-
0.3
0
0.3
0.6
0.9
1.2
1.5
1.8
2.1
2.4
2.7
3.0
3.3
Po
p
u
la
t
i
o
n
SMALL-SIGNAL STEP RESPONSE
100ns/div
10
mV
/
d
i
v
G = +1
R
L
= 10k
C
L
= 20pF
SMALL-SIGNAL STEP RESPONSE
200ns/div
10
mV
/
d
i
v
C
F
= 2pF
C
F
= 3pF
C
F
= 4pF
10k
C
F
C
L
20pF
G =
-
1
R
F
10k
O P A 7 25
OPA725, OPA2725
OPA726, OPA2726
SBOS278B - SEPTEMBER 2003 - REVISED JANUARY 2004
www.ti.com
10
TYPICAL CHARACTERISTICS (continued)
At TA = +25
C, VS =
6V, RL = 10k
connected to VS/2, and VOUT = VS/2, unless otherwise noted.
LARGE-SIGNAL STEP RESPONSE
1V
/
d
i
v
400ns/div
10k
R
F
10k
C
F
4pF
C
L
20pF
G =
-
1
OPA725
OPA725, OPA2725
OPA726, OPA2726
SBOS278B - SEPTEMBER 2003 - REVISED JANUARY 2004
www.ti.com
11
APPLICATIONS INFORMATION
OPA725 and OPA726 series 20MHz CMOS op amps have
a fast slew rate, low noise, and excellent PSRR, CMRR,
and A
OL
. These op amps can operate on typically 4.3mA
quiescent current from a single (or split) supply in the range
of 4V to 12V (
2V to
6V), making them highly versatile
and easy to use. They are stable in a unity-gain
configuration.
Power-supply pins should be bypassed with 1nF ceramic
capacitors in parallel with 1
F tantalum capacitors.
OPERATING VOLTAGE
OPA725 series op amps are specified from 4V to 12V
supplies over a temperature range of -40
C to +125
C.
They will operate well in
5V or +5V to +12V power-supply
systems. Parameters that vary significantly with operating
voltage or temperature are shown in the Typical
Characteristics.
ENABLE/SHUTDOWN
OPA725 series op amps require approximately 4.3mA
quiescent current. The enable/shutdown feature of the
OPA726 allows the op amp to be shut off to reduce this
current to approximately 6
A.
The enable/shutdown input is referenced to the Enable
Reference Pin, DGND (see Pin Configurations). This pin
can be connected to logic ground in dual-supply op amp
configurations to avoid level-shifting the enable logic
signal, as shown in Figure 1.
The Enable Reference Pin voltage, V
DGND
, must not
exceed (V+) - 2V. It may be set as low as V-. The amplifier
is enabled when the Enable Pin voltage is greater than
V
DGND
+ 2V. The amplifier is disabled (shutdown) if the
Enable Pin voltage is less than V
DGND
+ 0.8V. The Enable
Pin is connected to internal pull-up circuitry and will enable
the device if left unconnected.
COMMON-MODE VOLTAGE RANGE
The input common-mode voltage range of the OPA725
and OPA726 series extends from V- to (V+) - 2V.
Common-mode rejection is excellent throughout the input
voltage range from V- to (V+) - 3V. CMRR decreases
somewhat as the common-mode voltage extends to
(V+) - 2V, but remains very good and is tested throughout
this range. See the Electrical Characteristics table for
details.
DGND
Digital
Logic
Enable
OPA726
+12V
a) Single-Supply Configuration
b) Dual-Supply Configuration
DGND
Digital
Logic
Enable
OPA726
+5V
-
5V
V
OUT
V
OUT
Figure 1. Enable Reference Pin Connection for
Single- and Dual-Supply Configurations
INPUT OVER-VOLTAGE PROTECTION
Device inputs are protected by ESD diodes that will
conduct if the input voltages exceed the power supplies by
more than approximately 300mV. Momentary voltages
greater than 300mV beyond the power supply can be
tolerated if the current is limited to 10mA. This is easily
accomplished with an input resistor in series with the op
amp, as shown in Figure 2. The OPA725 series features
no phase inversion when the inputs extend beyond
supplies, if the input is current limited.
R
OPA725
V+
V
-
V
IN
V
OUT
10mA max
I
OVERLOAD
Figure 2. Input Current Protection for Voltages
Exceeding the Supply Voltage
OPA725, OPA2725
OPA726, OPA2726
SBOS278B - SEPTEMBER 2003 - REVISED JANUARY 2004
www.ti.com
12
RAIL-TO-RAIL OUTPUT
A class AB output stage with common-source transistors
is used to achieve rail-to-rail output. This output stage is
capable of driving heavy loads connected to any point
between V+ and V-. For light resistive loads ( > 100k
),
the output voltage can swing to 150mV (175mV for dual)
from the supply rail, while still maintaining excellent
linearity (A
OL
> 110dB). With 1k
(2k
for dual) resistive
loads, the output is specified to swing to within 250mV from
the supply rails with excellent linearity (see the Typical
Characteristics curve Output Voltage Swing vs Output
Current).
CAPACITIVE LOAD AND STABILITY
Capacitive load drive is dependent upon gain and the
overshoot requirements of the application. Increasing the
gain enhances the ability of the amplifier to drive greater
capacitive loads (see the Typical Characteristics curve
Small-Signal Overshoot vs Capacitive Load).
One method of improving capacitive load drive in the
unity-gain configuration is to insert a 10
to 20
resistor
inside the feedback loop, as shown in Figure 3. This
reduces ringing with large capacitive loads while
maintaining DC accuracy.
R
S
20
OPA725
C
L
R
L
V
IN
V
OUT
V+
Figure 3. Series Resistor in Unity-Gain Buffer
Configuration Improves Capacitive Load Drive
DRIVING FAST 16-BIT ADCs
The OPA725 series is optimized for driving fast 16-bit
ADCs such as the ADS8342. The OPA725 op amps buffer
the converter input capacitance and resulting charge
injection, while providing signal gain. Figure 4 shows the
OPA725 in a single-ended method of interfacing to the
ADS8342 16-bit, 250kSPS, 4-channel ADC with an input
range of
2.5V. The OPA725 has demonstrated excellent
settling time to the 16-bit level within the 600ns acquisition
time of the ADS8342. The RC filter, shown in Figure 4, has
been carefully tuned for best noise and settling
performance. It may need to be adjusted for different op
amp configurations. Please refer to the ADS8342 data
sheet (available for download at www.ti.com) for additional
information on this product.
75
OPA725
ADS8342
16-Bit ADC
AIN
Common
330pF
V
IN
2.5V
+5V
-
5V
+5V
-
5V
Figure 4. OPA725 Driving an ADC
TRANSIMPEDANCE AMPLIFIER
Wide bandwidth, low input bias current, and low input
voltage and current noise make the OPA725 an ideal
wideband photodiode transimpedance amplifier. Low-
voltage noise is important because photodiode capaci-
tance causes the effective noise gain of the circuit to
increase at high frequency.
The key elements to a transimpedance design, as shown
in Figure 5, are the expected diode capacitance (C
D
),
which should include the parasitic input common-mode
and differential-mode input capacitance (4pF + 5pF for the
OPA725); the desired transimpedance gain (R
F
); and the
GBW for the OPA725 (20MHz). With these three variables
set, the feedback capacitor value (C
F
) can be set to control
the frequency response. C
F
includes the stray capacitance
of R
F
, which is 0.2pF for a typical surface-mount resistor.
OPA725
V
OUT
10M
+5V
-
5V
C
D
R
F
C
F
(1)
< 1pF
NOTE: (1) C
F
is optional to prevent gain peaking.
It includes the stray capacitance of R
F
.
Figure 5. Dual-Supply Transimpedance Amplifier
OPA725, OPA2725
OPA726, OPA2726
SBOS278B - SEPTEMBER 2003 - REVISED JANUARY 2004
www.ti.com
13
To achieve a maximally-flat, 2nd-order Butterworth
frequency response, the feedback pole should be set to:
1
2
p
R
F
C
F
+
GBW
4
p
R
F
C
D
Bandwidth is calculated by:
f
*
3dB
+
GBW
2
p
R
F
C
D
Hz
For even higher transimpedance bandwidth, the
high-speed CMOS OPA354 (100MHz GBW), OPA300
(180 MHz GBW), OPA355 (200MHz GBW), or OPA656,
OPA657 (400MHz GBW) may be used.
For single-supply applications, the +IN input can be biased
with a positive dc voltage to allow the output to reach true
zero when the photodiode is not exposed to any light, and
respond without the added delay that results from coming
out of the negative rail. (Refer to Figure 6.) This bias
voltage also appears across the photodiode, providing a
reverse bias for faster operation.
OPA725
V
OUT
10M
V+
R
F
C
F
(1)
< 1pF
NOTE: (1) C
F
is optional to prevent gain peaking.
It includes the stray capacitance of R
F
.
+V
Bias
Figure 6. Single-Supply Transimpedance
Amplifier
For additional information, refer to Application Bulletin
SBOA055, Compensate Transimpedance Amplifiers
Intuitively, available for download at www.ti.com.
OPTIMIZING THE TRANSIMPEDANCE
CIRCUIT
To achieve the best performance, components should be
selected according to the following guidelines:
1.
For lowest noise, select R
F
to create the total required
gain. Using a lower value for R
F
and adding gain after
the transimpedance amplifier generally produces
poorer noise performance. The noise produced by R
F
increases with the square-root of R
F
, whereas the
signal increases linearly. Therefore, signal-to-noise
ratio is improved when all the required gain is placed
in the transimpedance stage.
2.
Minimize photodiode capacitance and stray
capacitance at the summing junction (inverting input).
This capacitance causes the voltage noise of the op
amp to be amplified (increasing amplification at high
frequency). Using a low-noise voltage source to
reverse-bias a photodiode can significantly reduce its
capacitance. Smaller photodiodes have lower
capacitance. Use optics to concentrate light on a small
photodiode.
3.
Noise increases with increased bandwidth. Limit the
circuit bandwidth to only that required. Use a capacitor
across the R
F
to limit bandwidth, even if not required
for stability.
4.
Circuit board leakage can degrade the performance of
an otherwise well-designed amplifier. Clean the circuit
board carefully. A circuit board guard trace that
encircles the summing junction and is driven at the
same voltage can help control leakage.
For additional information, refer to the Application Bulletins
Noise Analysis of FET Transimpedance Amplifiers
(SBOA060), and Noise Analysis for High-Speed Op Amps
(SBOA066), available for download at the TI web site.
(1)
(2)
OPA725, OPA2725
OPA726, OPA2726
SBOS278B - SEPTEMBER 2003 - REVISED JANUARY 2004
www.ti.com
14
NOTE: FilterPro is a low-pass filter design program available for download at no cost from TI's web site (www.ti.com). The program can be used
to determine component values for other cutoff frequencies or filter types.
DC Gain = 1
C
1
1nF
C
2
330pF
R
2
15.9k
R
1
1.93k
2.2nF
C
3
C
4
100pF
R
4
22.3k
R
3
2.07k
Cutoff Frequency = 50kHz
V
OUT
1/2
OPA2725
1/2
OPA2725
Figure 7. Four-Pole Butterworth Sallen-Key Low-Pass Filter
PACKAGING INFORMATION
Orderable Device
Status
(1)
Package
Type
Package
Drawing
Pins Package
Qty
Eco Plan
(2)
Lead/Ball Finish
MSL Peak Temp
(3)
OPA2725AID
ACTIVE
SOIC
D
8
100
None
CU NIPDAU
Level-3-240C-168 HR
OPA2725AIDGKR
ACTIVE
MSOP
DGK
8
2500
None
CU NIPDAU
Level-1-240C-UNLIM
OPA2725AIDGKT
ACTIVE
MSOP
DGK
8
250
None
CU NIPDAU
Level-1-240C-UNLIM
OPA2725AIDR
ACTIVE
SOIC
D
8
2500
None
CU NIPDAU
Level-3-240C-168 HR
OPA2726AIDGSR
ACTIVE
MSOP
DGS
10
2500
None
CU NIPDAU
Level-1-240C-UNLIM
OPA2726AIDGST
ACTIVE
MSOP
DGS
10
250
None
CU NIPDAU
Level-1-240C-UNLIM
OPA725AID
ACTIVE
SOIC
D
8
100
None
CU NIPDAU
Level-3-240C-168 HR
OPA725AIDBVR
ACTIVE
SOT-23
DBV
5
3000
None
CU NIPDAU
Level-1-240C-UNLIM
OPA725AIDBVT
ACTIVE
SOT-23
DBV
5
250
None
CU NIPDAU
Level-1-240C-UNLIM
OPA725AIDR
ACTIVE
SOIC
D
8
2500
None
CU NIPDAU
Level-3-240C-168 HR
OPA726AID
ACTIVE
SOIC
D
8
100
None
CU NIPDAU
Level-3-240C-168 HR
OPA726AIDGKR
ACTIVE
MSOP
DGK
8
2500
None
CU NIPDAU
Level-2-240C-1 YEAR
OPA726AIDGKT
ACTIVE
MSOP
DGK
8
250
None
CU NIPDAU
Level-2-240C-1 YEAR
OPA726AIDR
ACTIVE
SOIC
D
8
2500
None
CU NIPDAU
Level-3-240C-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
reasonable steps to provide representative and accurate information but may not have conducted destructive testing or chemical analysis on
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
4-Mar-2005
Addendum-Page 1
IMPORTANT NOTICE
Texas Instruments Incorporated and its subsidiaries (TI) reserve the right to make corrections, modifications,
enhancements, improvements, and other changes to its products and services at any time and to discontinue
any product or service without notice. Customers should obtain the latest relevant information before placing
orders and should verify that such information is current and complete. All products are sold subject to TI's terms
and conditions of sale supplied at the time of order acknowledgment.
TI warrants performance of its hardware products to the specifications applicable at the time of sale in
accordance with TI's standard warranty. Testing and other quality control techniques are used to the extent TI
deems necessary to support this warranty. Except where mandated by government requirements, testing of all
parameters of each product is not necessarily performed.
TI assumes no liability for applications assistance or customer product design. Customers are responsible for
their products and applications using TI components. To minimize the risks associated with customer products
and applications, customers should provide adequate design and operating safeguards.
TI does not warrant or represent that any license, either express or implied, is granted under any TI patent right,
copyright, mask work right, or other TI intellectual property right relating to any combination, machine, or process
in which TI products or services are used. Information published by TI regarding third-party products or services
does not constitute a license from TI to use such products or services or a warranty or endorsement thereof.
Use of such information may require a license from a third party under the patents or other intellectual property
of the third party, or a license from TI under the patents or other intellectual property of TI.
Reproduction of information in TI data books or data sheets is permissible only if reproduction is without
alteration and is accompanied by all associated warranties, conditions, limitations, and notices. Reproduction
of this information with alteration is an unfair and deceptive business practice. TI is not responsible or liable for
such altered documentation.
Resale of TI products or services with statements different from or beyond the parameters stated by TI for that
product or service voids all express and any implied warranties for the associated TI product or service and
is an unfair and deceptive business practice. TI is not responsible or liable for any such statements.
Following are URLs where you can obtain information on other Texas Instruments products and application
solutions:
Products
Applications
Amplifiers
amplifier.ti.com
Audio
www.ti.com/audio
Data Converters
dataconverter.ti.com
Automotive
www.ti.com/automotive
DSP
dsp.ti.com
Broadband
www.ti.com/broadband
Interface
interface.ti.com
Digital Control
www.ti.com/digitalcontrol
Logic
logic.ti.com
Military
www.ti.com/military
Power Mgmt
power.ti.com
Optical Networking
www.ti.com/opticalnetwork
Microcontrollers
microcontroller.ti.com
Security
www.ti.com/security
Telephony
www.ti.com/telephony
Video & Imaging
www.ti.com/video
Wireless
www.ti.com/wireless
Mailing Address:
Texas Instruments
Post Office Box 655303 Dallas, Texas 75265
Copyright
2005, Texas Instruments Incorporated
PDF 
ZIP