1
2
3
4
8
7
6
5
V+
Out B
In B
+In B
Out A
In A
+In A
V
OPA2353
SO-8, MSOP-8
A
B
1
2
3
4
8
7
6
5
NC
V+
Output
NC
NC
In
+In
V
OPA353
SO-8
High-Speed, Single-Supply, Rail-to-Rail
OPERATIONAL AMPLIFIERS
Micro
Amplifier
TM
Series
1998 Burr-Brown Corporation
PDS-1479B
Printed in U.S.A. March, 1999
OPA353
OPA2353
OPA4353
FEATURES
q
RAIL-TO-RAIL INPUT
q
RAIL-TO-RAIL OUTPUT (within 10mV)
q
WIDE BANDWIDTH: 44MHz
q
HIGH SLEW RATE: 22V/
s
q
LOW NOISE: 5nV/
Hz
q
LOW THD+NOISE: 0.0006%
q
UNITY-GAIN STABLE
q
Micro
SIZE PACKAGES
q
SINGLE, DUAL, AND QUAD
APPLICATIONS
q
CELL PHONE PA CONTROL LOOPS
q
DRIVING A/D CONVERTERS
q
VIDEO PROCESSING
q
DATA ACQUISITION
q
PROCESS CONTROL
q
AUDIO PROCESSING
q
COMMUNICATIONS
q
ACTIVE FILTERS
q
TEST EQUIPMENT
DESCRIPTION
OPA353 series rail-to-rail CMOS operational amplifi-
ers are designed for low cost, miniature applications.
They are optimized for low voltage, single-supply op-
eration. Rail-to-rail input/output, low noise (5nV/
Hz),
and high speed operation (44MHz, 22V/
s) make them
ideal for driving sampling analog-to-digital converters.
They are also well suited for cell phone PA control
loops and video processing (75
drive capability) as
well as audio and general purpose applications. Single,
dual, and quad versions have identical specifications
for design flexibility.
The OPA353 series operates on a single supply as low as
2.5V with an input common-mode voltage range that
extends 300mV beyond the supply rails. Output voltage
swing is to within 10mV of the supply rails with a 10k
load. Dual and quad designs feature completely indepen-
dent circuitry for lowest crosstalk and freedom from
interaction.
The single (OPA353) packages are the tiny 5-lead SOT-
23-5 surface mount and SO-8 surface mount. The dual
(OPA2353) comes in the miniature MSOP-8 surface
mount and SO-8 surface mount. The quad (OPA4353)
packages are the space-saving SSOP-16 surface mount
and SO-14 surface mount. All are specified from 40
C
to +85
C and operate from 55
C to +125
C.
International Airport Industrial Park Mailing Address: PO Box 11400, Tucson, AZ 85734 Street Address: 6730 S. Tucson Blvd., Tucson, AZ 85706 Tel: (520) 746-1111
Twx: 910-952-1111 Internet: http://www.burr-brown.com/ Cable: BBRCORP Telex: 066-6491 FAX: (520) 889-1510 Immediate Product Info: (800) 548-6132
(SO-14 package not shown)
OPA2353
OPA4353
OPA4353
1
2
3
4
5
6
7
8
16
15
14
13
12
11
10
9
Out D
In D
+In D
V
+In C
In C
Out C
NC
Out A
In A
+In A
+V
+In B
In B
Out B
NC
OPA4353
SSOP-16
A
D
B
C
1
2
3
5
4
V+
In
Out
V
+In
OPA353
SOT-23-5
For most current data sheet and other product
information, visit www.burr-brown.com
SPICE Model available at www.burr-brown.com
2
OPA353, 2353, 4353
SPECIFICATIONS: V
S
= 2.7V to 5.5V
At T
A
= +25
C, R
L
= 1k
connected to V
S
/ 2 and V
OUT
= V
S
/ 2, unless otherwise noted.
Boldface limits apply over the specified temperature range, T
A
= 40
C to +85
C. V
S
= 5V.
OPA353NA, UA
OPA2353EA, UA
OPA4353EA, UA
PARAMETER
CONDITION
MIN
TYP
(1)
MAX
UNITS
OFFSET VOLTAGE
Input Offset Voltage
V
OS
V
S
= 5V
3
8
mV
T
A
= 40
C to +85
C
10
mV
vs Temperature
T
A
= 40
C to +85
C
5
V/
C
vs Power Supply Rejection Ratio
PSRR
V
S
= 2.7V to 5.5V, V
CM
= 0V
40
150
V/V
T
A
= 40
C to +85
C
V
S
= 2.7V to 5.5V, V
CM
= 0V
175
V/V
Channel Separation (dual, quad)
dc
0.15
V/V
INPUT BIAS CURRENT
Input Bias Current
I
B
0.5
10
pA
T
A
= 40
C to +85
C
See Typical Curve
Input Offset Current
I
OS
0.5
10
pA
NOISE
Input Voltage Noise, f = 100Hz to 400kHz
4
Vrms
Input Voltage Noise Density, f = 10kHz
e
n
7
nV/
Hz
f = 100kHz
5
nV/
Hz
Current Noise Density, f = 10kHz
i
n
4
fA/
Hz
INPUT VOLTAGE RANGE
Common-Mode Voltage Range
V
CM
0.1
(V+) + 0.1
V
Common-Mode Rejection Ratio
CMRR
0.1V < V
CM
< (V+) 2.4V
76
86
dB
V
S
= 5V, 0.1V < V
CM
< 5.1V
60
74
dB
T
A
= 40
C to +85
C
V
S
= 5V, 0.1V < V
CM
< 5.1V
58
dB
INPUT IMPEDANCE
Differential
10
13
|| 2.5
|| pF
Common-Mode
10
13
|| 6.5
|| pF
OPEN-LOOP GAIN
Open-Loop Voltage Gain
A
OL
R
L
= 10k
, 50mV < V
O
< (V+) 50mV
100
122
dB
T
A
= 40
C to +85
C
R
L
= 10k
, 50mV < V
O
< (V+) 50mV
100
dB
R
L
= 1k
, 200mV < V
O
< (V+) 200mV
100
120
dB
T
A
= 40
C to +85
C
R
L
= 1k
, 200mV < V
O
< (V+) 200mV
100
dB
FREQUENCY RESPONSE
C
L
= 100pF
Gain-Bandwidth Product
GBW
G = 1
44
MHz
Slew Rate
SR
G = 1
22
V/
s
Settling Time, 0.1%
G =
1, 2V Step
0.22
s
0.01%
G =
1, 2V Step
0.5
s
Overload Recovery Time
V
IN
G = V
S
0.1
s
Total Harmonic Distortion + Noise
THD+N
R
L
= 600
, V
O
= 2.5Vp-p
(2)
, G = 1, f = 1kHz
0.0006
%
Differential Gain Error
G = 2, R
L
= 600
, V
O
= 1.4V
(3)
0.17
%
Differential Phase Error
G = 2, R
L
= 600
, V
O
= 1.4V
(3)
0.17
deg
OUTPUT
Voltage Output Swing from Rail
(4)
V
OUT
R
L
= 10k
, A
OL
100dB
10
50
mV
T
A
= 40
C to +85
C
R
L
= 10k
,
A
OL
100dB
50
mV
R
L
= 1k
,
A
OL
100dB
25
200
mV
T
A
= 40
C to +85
C
R
L
= 1k
, A
OL
100dB
200
mV
Output Current
I
OUT
40
(5)
mA
Short-Circuit Current
I
SC
80
mA
Capacitive Load Drive
C
LOAD
See Typical Curve
POWER SUPPLY
Operating Voltage Range
V
S
T
A
= 40
C to +85
C
2.7
5.5
V
Minimum Operating Voltage
2.5
V
Quiescent Current (per amplifier)
I
Q
I
O
= 0
5.2
8
mA
T
A
= 40
C to +85
C
I
O
= 0
9
mA
TEMPERATURE RANGE
Specified Range
40
+85
C
Operating Range
55
+125
C
Storage Range
55
+125
C
Thermal Resistance
JA
SOT-23-5
200
C/W
MSOP-8 Surface Mount
150
C/W
SO-8 Surface Mount
150
C/W
SSOP-16 Surface Mount
100
C/W
SO-14 Surface Mount
100
C/W
NOTES: (1) V
S
= +5V. (2) V
OUT
= 0.25V to 2.75V. (3) NTSC signal generator used. See Figure 6 for test circuit. (4) Output voltage swings are measured between
the output and power supply rails. (5) See typical performance curve, "Output Voltage Swing vs Output Swing."
3
OPA353, 2353, 4353
PACKAGE/ORDERING INFORMATION
Supply Voltage ................................................................................... 5.5V
Signal Input Terminals, Voltage
(2)
.................. (V) 0.3V to (V+) + 0.3V
Current
(2)
.................................................... 10mA
Output Short-Circuit
(3)
.............................................................. Continuous
Operating Temperature .................................................. 55
C to +125
C
Storage Temperature ..................................................... 55
C to +125
C
Junction Temperature ...................................................................... 150
C
Lead Temperature (soldering, 10s) ................................................. 300
C
NOTES: (1) Stresses above these ratings may cause permanent damage.
Exposure to absolute maximum conditions for extended periods may de-
grade device reliability. (2) Input terminals are diode-clamped to the power
supply rails. Input signals that can swing more than 0.3V beyond the supply
rails should be current-limited to 10mA or less. (3) Short circuit to ground,
one amplifier per package.
ABSOLUTE MAXIMUM RATINGS
(1)
PIN CONFIGURATION
Top View
SO-14
The information provided herein is believed to be reliable; however, BURR-BROWN assumes no responsibility for inaccuracies or omissions. BURR-BROWN assumes no responsibility
for the use of this information, and all use of such information shall be entirely at the user's own risk. Prices and specifications are subject to change without notice. No patent rights or
licenses to any of the circuits described herein are implied or granted to any third party. BURR-BROWN does not authorize or warrant any BURR-BROWN product for use in life support
devices and/or systems.
ELECTROSTATIC
DISCHARGE SENSITIVITY
This integrated circuit can be damaged by ESD. Burr-Brown
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 degrada-
tion 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.
1
2
3
4
5
6
7
14
13
12
11
10
9
8
Out D
In D
+In D
V
+In C
In C
Out C
Out A
In A
+In A
V+
+In B
In B
Out B
OPA4353
A
D
B
C
PACKAGE
SPECIFIED
DRAWING
TEMPERATURE
PACKAGE
ORDERING
TRANSPORT
PRODUCT
PACKAGE
NUMBER
(1)
RANGE
MARKING
NUMBER
(2)
MEDIA
Single
OPA353NA
5-Lead SOT-23-5
331
40
C to +85
C
D53
OPA353NA /250
Tape and Reel
"
"
"
"
"
OPA353NA /3K
Tape and Reel
OPA353UA
SO-8 Surface Mount
182
40
C to +85
C
OPA353UA
OPA353UA
Rails
"
"
"
"
"
OPA353UA /2K5
Tape and Reel
Dual
OPA2353EA
MSOP-8 Surface Mount
337
40
C to +85
C
E53
OPA2353EA /250
Tape and Reel
"
"
"
"
"
OPA2353EA/2K5
Tape and Reel
OPA2353UA
SO-8 Surface Mount
182
40
C to +85
C
OPA2353UA
OPA2353UA
Rails
"
"
"
"
"
OPA2353UA/2K5
Tape and Reel
Quad
OPA4353EA
SSOP-16 Surface Mount
322
40
C to +85
C
OPA4353EA
OPA4353EA /250
Tape and Reel
"
"
"
"
"
OPA4353EA/2K5
Tape and Reel
OPA4353UA
SO-14 Surface Mount
235
40
C to +85
C
OPA4353UA
OPA4353UA
Rails
"
"
"
"
"
OPA4353UA/2K5
Tape and Reel
NOTES: (1) For detailed drawing and dimension table, please see end of data sheet, or Appendix C of Burr-Brown IC Data Book. (2) Models with a slash (/) are
available only in Tape and Reel in the quantities indicated (e.g., /2K5 indicates 2500 devices per reel). Ordering 2500 pieces of "OPA2353EA/2K5" will get a single
2500-piece Tape and Reel. For detailed Tape and Reel mechanical information, refer to Appendix B of Burr-Brown IC Data Book.
4
OPA353, 2353, 4353
TYPICAL PERFORMANCE CURVES
At T
A
= +25
C, V
S
= +5V, and R
L
= 1k
connected to V
S
/2, unless otherwise noted.
OPEN-LOOP GAIN/PHASE vs FREQUENCY
0.1
1
160
140
120
100
80
60
40
20
0
Voltage Gain (dB)
0
45
90
135
180
Phase (
)
Frequency (Hz)
10
100
1k
10k
100k
1M
10M
100M
G
POWER SUPPLY AND COMMON-MODE
REJECTION RATIO vs FREQUENCY
100
90
80
70
60
50
40
30
20
10
0
PSRR, CMRR (dB)
Frequency (Hz)
10
100
1k
10k
100k
1M
10M
PSRR
CMRR
(V
S
= +5V
V
CM
= 0.1V to 5.1V)
INPUT VOLTAGE AND CURRENT NOISE
SPECTRAL DENSITY vs FREQUENCY
100k
10k
1k
100
10
1
10k
1k
100
10
1
0.1
Voltage Noise (nV
Hz)
Frequency (Hz)
10
100
1k
10k
100k
1M
10M
Current Noise (fA
Hz)
Voltage Noise
Current Noise
HARMONIC DISTORTION + NOISE vs FREQUENCY
1
(40dBc)
0.1
(60dBc)
0.01
(80dBc)
0.001
(100dBc)
0.0001
(120dBc)
Harmonic Distortion (%)
Frequency (Hz)
1k
10k
100k
1M
G = 1
V
O
= 2.5Vp-p
R
L
= 600
3rd Harmonic
2nd Harmonic
TOTAL HARMONIC DISTORTION + NOISE
vs FREQUENCY
1
0.1
0.01
0.001
0.0001
THD+N (%)
Frequency (Hz)
10
100
1k
10k
100k
R
L
= 600
G = 100, 3Vp-p (V
O
= 1V to 4V)
G = 10, 3Vp-p (V
O
= 1V to 4V)
G = 1, 3Vp-p (V
O
= 1V to 4V)
Input goes through transition region
G = 1, 2.5Vp-p (V
O
= 0.25V to 2.75V)
Input does NOT go through transition region
CHANNEL SEPARATION vs FREQUENCY
Frequency (Hz)
Channel Separation (dB)
140
130
120
110
100
90
80
70
60
100
10
1k
1M
100k
10k
10M
Dual and Quad
Versions
5
OPA353, 2353, 4353
TYPICAL PERFORMANCE CURVES
(CONT)
At T
A
= +25
C, V
S
= +5V, and R
L
= 1k
connected to V
S
/2, unless otherwise noted.
DIFFERENTIAL GAIN/PHASE vs RESISTIVE LOAD
0.5
0.4
0.3
0.2
0.1
0
Differential Gain (%)
Differential Phase (
)
Resistive Load (
)
0
100
200
300
500
400
600
800
700
900 1000
G = 2
V
O
= 1.4V
NTSC Signal Generator
See Figure 6 for test circuit.
Phase
Gain
OPEN-LOOP GAIN vs TEMPERATURE
130
125
120
115
110
Open-Loop Gain (dB)
Temperature (
C)
75
50
25
0
25
50
75
100
125
R
L
= 600
R
L
= 1k
R
L
= 10k
COMMON-MODE AND POWER SUPPLY
REJECTION RATIO vs TEMPERATURE
90
80
70
60
50
CMRR (dB)
110
100
90
80
70
PSRR (dB)
Temperature (
C)
75
50
25
0
25
50
75
100
125
CMRR, V
S
= 5V
(V
CM
= 0.1V to +5.1V)
PSRR
SLEW RATE vs TEMPERATURE
Temperature (
C)
Slew Rate (V/
s)
40
35
30
25
20
15
10
5
0
75
50
25
0
25
50
75
100
125
Negative Slew Rate
Positive Slew Rate
QUIESCENT CURRENT AND
SHORT-CIRCUIT CURRENT vs TEMPERATURE
Temperature (
C)
Quiescent Current (mA)
7.0
6.5
6.0
5.5
5.0
4.5
4.0
3.5
100
90
80
70
60
50
40
30
Short-Circuit Current (mA)
75
50
25
0
25
50
75
100
125
I
Q
+I
SC
I
SC
QUIESCENT CURRENT vs SUPPLY VOLTAGE
Supply Voltage (V)
Quiescent Current (mA)
6.0
5.5
5.0
4.5
4.0
3.5
3.0
2.0
2.5
3.0
3.5
4.0
4.5
5.0
5.5
Per Amplifier
6
OPA353, 2353, 4353
TYPICAL PERFORMANCE CURVES
(CONT)
At T
A
= +25
C, V
S
= +5V, and R
L
= 1k
connected to V
S
/2, unless otherwise noted.
INPUT BIAS CURRENT vs TEMPERATURE
Input Bias Current (pA)
Temperature (
C)
75
50
25
0
25
50
75
100
125
1k
100
10
1
0.1
INPUT BIAS CURRENT
vs INPUT COMMON-MODE VOLTAGE
Common-Mode Voltage (V)
Input Bias Current (pA)
1.5
1.0
0.5
0.0
0.5
0.5 0.0 0.5 1.0
2.0
1.5
2.5 3.0 3.5 4.0
5.0
4.5
5.5
CLOSED-LOOP OUTPUT IMPEDANCE vs FREQUENCY
Frequency (Hz)
Output Impedance (
)
100
10
1
0.1
0.01
0.001
0.0001
1
10
100
1k
10k
100k
1M
10M
100M
G = 100
G = 10
G = 1
MAXIMUM OUTPUT VOLTAGE vs FREQUENCY
100M
1M
10M
Frequency (Hz)
100k
6
5
4
3
2
1
0
Output Voltage (Vp-p)
Maximum output
voltage without
slew rate-induced
distortion.
V
S
= 2.7V
V
S
= 5.5V
OUTPUT VOLTAGE SWING vs OUTPUT CURRENT
Output Current (mA)
Output Voltage (V)
V+
(V+)1
(V+)2
(V)+2
(V)+1
(V)
0
10
20
30
40
+25
C
+125
C
55
C
55
C
+125
C
+25
C
Depending on circuit configuration
(including closed-loop gain) performance
may be degraded in shaded region.
OPEN-LOOP GAIN vs OUTPUT VOLTAGE SWING
140
130
120
110
100
90
80
70
60
Open-Loop Gain (dB)
Output Voltage Swing from Supply Rails (mV)
0
20
40
60
100
80
120
160
140
180
200
I
OUT
= 4.2mA
I
OUT
= 250
A
I
OUT
= 2.5mA
7
OPA353, 2353, 4353
TYPICAL PERFORMANCE CURVES
(CONT)
At T
A
= +25
C, V
S
= +5V, and R
L
= 1k
connected to V
S
/2, unless otherwise noted.
SMALL-SIGNAL STEP RESPONSE
C
L
= 100pF
100ns/div
50mV/div
LARGE-SIGNAL STEP RESPONSE
C
L
= 100pF
200ns/div
1V/div
Offset Voltage Drift (
V/
C)
OFFSET VOLTAGE DRIFT
PRODUCTION DISTRIBUTION
35
30
25
20
15
10
5
0
0
1
2
3
4
5
6
7
8
9
10 11 12 13 14 15
Percent of Amplifiers (%)
Typical production
distribution of
packaged units.
SMALL-SIGNAL OVERSHOOT vs LOAD CAPACITANCE
1M
100
1k
10k
100k
Load Capacitance (pF)
10
80
70
60
50
40
30
20
10
0
Overshoot (%)
G = 1
G = 1
G =
10
SETTLING TIME vs CLOSED-LOOP GAIN
10
1
0.1
Settling Time (
s)
Closed-Loop Gain (V/V)
1
10
100
0.1%
0.01%
Offset Voltage (mV)
OFFSET VOLTAGE PRODUCTION DISTRIBUTION
25
20
15
10
5
0
8 7 6 5 4 3 2 1 0
1
2
3
4
5
6
7
8
Percent of Units (%)
Typical production
distribution of
packaged units.
8
OPA353, 2353, 4353
APPLICATIONS INFORMATION
OPA353 series op amps are fabricated on a state-of-the-art
0.6 micron CMOS process. They are unity-gain stable and
suitable for a wide range of general purpose applications.
Rail-to-rail input/output make them ideal for driving sam-
pling A/D converters. They are well suited for controlling
the output power in cell phones. These applications often
require high speed and low noise. In addition, the OPA353
series offers a low cost solution for general purpose and
consumer video applications (75
drive capability).
Excellent ac performance makes the OPA353 series well
suited for audio applications. Their bandwidth, slew rate,
low noise (5nV/
Hz), low THD (0.0006%), and small pack-
age options are ideal for these applications. The class AB
output stage is capable of driving 600
loads connected to
any point between V+ and ground.
Rail-to-rail input and output swing significantly increases
dynamic range, especially in low voltage supply applica-
tions. Figure 1 shows the input and output waveforms for
the OPA353 in unity-gain configuration. Operation is
from a single +5V supply with a 1k
load connected to
V
S
/2. The input is a 5Vp-p sinusoid. Output voltage is
approximately 4.95Vp-p.
Power supply pins should be bypassed with 0.01
F ceramic
capacitors.
OPERATING VOLTAGE
OPA353 series op amps are fully specified from +2.7V to
+5.5V. However, supply voltage may range from +2.5V to
+5.5V. Parameters are guaranteed over the specified supply
range--a unique feature of the OPA353 series. In addition,
many specifications apply from 40
C to +85
C. Most
behavior remains virtually unchanged throughout the full
operating voltage range. Parameters which vary signifi-
cantly with operating voltages or temperature are shown in
the typical performance curves.
RAIL-TO-RAIL INPUT
The guaranteed input common-mode voltage range of the
OPA353 series extends 100mV beyond the supply rails. This
is achieved with a complementary input stage--an
N-channel input differential pair in parallel with a P-channel
differential pair (see Figure 2). The N-channel pair is active
for input voltages close to the positive rail, typically
(V+) 1.8V to 100mV above the positive supply, while the
P-channel pair is on for inputs from 100mV below the
negative supply to approximately (V+) 1.8V. There is a
small transition region, typically (V+) 2V to (V+) 1.6V, in
which both pairs are on. This 400mV transition region can
vary
400mV with process variation. Thus, the transition
region (both input stages on) can range from (V+) 2.4V to
(V+) 2.0V on the low end, up to (V+) 1.6V to (V+) 1.2V
on the high end.
FIGURE 2. Simplified Schematic.
V
BIAS1
V
BIAS2
V
IN
+
V
IN
Class AB
Control
Circuitry
V
O
V
(Ground)
V+
Reference
Current
0
5V
V
S
= +5, G = +1, R
L
= 1k
V
IN
1.25V/div
FIGURE 1. Rail-to-Rail Input and Output.
5V
0
V
OUT
9
OPA353, 2353, 4353
A double-folded cascode adds the signal from the two input
pairs and presents a differential signal to the class AB output
stage. Normally, input bias current is approximately 500fA.
However, large inputs (greater than 300mV beyond the
supply rails) can turn on the OPA353's input protection
diodes, causing excessive current to flow in or out of the
input pins. Momentary voltages greater than 300mV beyond
the power supply can be tolerated if the current on the input
pins is limited to 10mA. This is easily accomplished with an
input resistor as shown in Figure 3. Many input signals are
inherently current-limited to less than 10mA, therefore, a
limiting resistor is not required.
FEEDBACK CAPACITOR IMPROVES RESPONSE
For optimum settling time and stability with high-imped-
ance feedback networks, it may be necessary to add a
feedback capacitor across the feedback resistor, R
F
, as
shown in Figure 4. This capacitor compensates for the zero
created by the feedback network impedance and the
OPA353's input capacitance (and any parasitic layout
capacitance). The effect becomes more significant with
higher impedance networks.
FIGURE 3. Input Current Protection for Voltages Exceeding
the Supply Voltage.
RAIL-TO-RAIL OUTPUT
A class AB output stage with common-source transistors is
used to achieve rail-to-rail output. For light resistive loads
(>10k
), the output voltage swing is typically ten millivolts
from the supply rails. With heavier resistive loads (600
to
10k
), the output can swing to within a few tens of milli-
volts from the supply rails and maintain high open-loop
gain. See the typical performance curves "Output Voltage
Swing vs Output Current" and "Open-Loop Gain vs Output
Voltage."
CAPACITIVE LOAD AND STABILITY
OPA353 series op amps can drive a wide range of capacitive
loads. However, all op amps under certain conditions may
become unstable. Op amp configuration, gain, and load
value are just a few of the factors to consider when determin-
ing stability. An op amp in unity gain configuration is the
most susceptible to the effects of capacitive load. The
capacitive load reacts with the op amp's output impedance,
along with any additional load resistance, to create a pole in
the small-signal response which degrades the phase margin.
In unity gain, OPA353 series op amps perform well with
large capacitive loads. Increasing gain enhances the
amplifier's ability to drive more capacitance. The typical
performance curve "Small-Signal Overshoot vs Capacitive
Load" shows performance with a 1k
resistive load. In-
creasing load resistance improves capacitive load drive ca-
pability.
FIGURE 4. Feedback Capacitor Improves Dynamic Perfor-
mance.
It is suggested that a variable capacitor be used for the
feedback capacitor since input capacitance may vary be-
tween op amps and layout capacitance is difficult to
determine. For the circuit shown in Figure 4, the value of
the variable feedback capacitor should be chosen so that
the input resistance times the input capacitance of the
OPA353 (typically 9pF) plus the estimated parasitic layout
capacitance equals the feedback capacitor times the feed-
back resistor:
R
IN
C
IN
= R
F
C
F
where C
IN
is equal to the OPA353's input capacitance
(sum of differential and common-mode) plus the layout
capacitance. The capacitor can be varied until optimum
performance is obtained.
DRIVING A/D CONVERTERS
OPA353 series op amps are optimized for driving medium
speed (up to 500kHz) sampling A/D converters. However,
they also offer excellent performance for higher speed
converters. The OPA353 series provides an effective means
of buffering the A/D's input capacitance and resulting
charge injection while providing signal gain. For applica-
tions requiring high accuracy, the OPA350 series is recom-
mended.
5k
OPAx353
10mA max
V+
V
IN
V
OUT
I
OVERLOAD
OPA353
V+
V
OUT
V
IN
R
IN
R
IN
C
IN
= R
F
C
F
R
F
C
L
C
IN
C
IN
C
F
Where C
IN
is equal to the OPA353's input
capacitance (approximately 9pF) plus any
parastic layout capacitance.
10
OPA353, 2353, 4353
Figure 5 shows the OPA353 driving an ADS7861. The
ADS7861 is a dual, 12-bit, 500kHz sampling converter in
the small SSOP-24 package. When used with the miniature
package options of the OPA353 series, the combination is
ideal for space-limited and low power applications. For
further information consult the ADS7861 data sheet.
OUTPUT IMPEDANCE
The low frequency open-loop output impedance of the
OPA353's common-source output stage is approximately
1k
. When the op amp is connected with feedback, this
value is reduced significantly by the loop gain of the op
amp. For example, with 122dB of open-loop gain, the
output impedance is reduced in unity-gain to less than
0.001
. For each decade rise in the closed-loop gain, the
loop gain is reduced by the same amount which results in
a ten-fold increase in output impedance (see the typical
performance curve, "Output Impedance vs Frequency").
At higher frequencies, the output impedance will rise as
the open-loop gain of the op amp drops. However, at these
frequencies the output also becomes capacitive due to
parasitic capacitance. This prevents the output impedance
from becoming too high, which can cause stability prob-
lems when driving capacitive loads. As mentioned previ-
ously, the OPA353 has excellent capacitive load drive
capability for an op amp with its bandwidth.
VIDEO LINE DRIVER
Figure 6 shows a circuit for a single supply, G = 2 com-
posite video line driver. The synchronized outputs of a
composite video line driver extend below ground. As
shown, the input to the op amp should be ac-coupled and
shifted positively to provide adequate signal swing to
account for these negative signals in a single-supply con-
figuration.
The input is terminated with a 75
resistor and ac-coupled
with a 47
F capacitor to a voltage divider that provides the
dc bias point to the input. In Figure 6, this point is
approximately (V) + 1.7V. Setting the optimal bias point
requires some understanding of the nature of composite
video signals. For best performance, one should be careful
to avoid the distortion caused by the transition region of
the OPA353's complementary input stage. Refer to the
discussion of rail-to-rail input.
FIGURE 5. OPA4353 Driving Sampling A/D Converter.
1/4
OPA4353
V
IN
B1
2
3
4
2k
2k
C
B1
CH B1+
CH B1
CH B0+
CH B0
CH A1+
CH A1
CH A0+
CH A0
REF
IN
REF
OUT
Serial Data A
Serial Data B
BUSY
CLOCK
CS
RD
CONVST
A0
M0
M1
2
3
4
5
6
7
8
9
10
11
23
22
21
20
19
18
17
16
15
14
1/4
OPA4353
V
IN
B0
+5V
6
5
2k
2k
C
B0
1/4
OPA4353
V
IN
A1
9
10
8
7
2k
2k
C
A1
1/4
OPA4353
V
IN
A0
14
11
1
12
2k
2k
C
A0
0.1
F
0.1
F
+V
A
+V
D
24
13
Serial
Interface
DGND
AGND
ADS7861
V
IN
= 0V to 2.45V for 0V to 4.9V output.
Choose C
B1
, C
B0
, C
A1
, C
A0
to filter high frequency noise.
11
OPA353, 2353, 4353
FIGURE 6. Single-Supply Video Line Driver.
FIGURE 7. Two Op-Amp Instrumentation Amplifier With Improved High Frequency Common-Mode Rejection.
OPA353
V
O
10M
<1pF (prevents gain peaking)
+V
FIGURE 9. 10kHz Low-Pass Filter.
FIGURE 8. Transimpedance Amplifier.
FIGURE 10. 10kHz High-Pass Filter.
OPA353
+5V
V
OUT
+5V (pin 7)
Video
In
R
OUT
R
L
Cable
R
F
1k
R
G
1k
R
4
5k
R
3
5k
C
3
10
F
0.1
F
10
F
+
6
7
4
C
4
0.1
F
C
5
1000
F
C
2
47
F
R
2
5k
R
1
75
C
1
220
F
+2.5V
V
IN
C
2
270pF
C
1
1830pF
2.5V
R
2
49.9k
R
L
20k
OPA353
V
OUT
R
1
10.5k
+2.5V
V
IN
R
2
19.6k
R
1
2.74k
2.5V
C
2
1nF
R
L
20k
OPA353
V
OUT
C
1
4.7
F
1/2
OPA2353
1/2
OPA2353
R
3
25k
R
2
25k
R
G
R
1
100k
R
4
100k
R
L
10k
V
OUT
50k
G = 5 +
200k
R
G
+5V
+5V
REF1004-2.5
4
8
(2.5V)
PDF 
ZIP