High-Speed, Precision
DIFFERENCE AMPLIFIER
1999 Burr-Brown Corporation
PDS-1483B
Printed in U.S.A. March, 1999
FEATURES
q
DESIGNED FOR LOW COST
q
LOW OFFSET VOLTAGE:
500
V max
q
LOW OFFSET DRIFT:
2
V/
C
q
LOW GAIN ERROR:
0.05% max
q
WIDE BANDWIDTH: 3MHz
q
HIGH SLEW RATE: 14V/
s
q
FAST SETTLING TIME: 3
s to 0.01%
q
WIDE SUPPLY RANGE:
4V to
18V
q
LOW QUIESCENT CURRENT: 2.4mA
q
SO-8 SURFACE-MOUNT PACKAGE
INA157
DESCRIPTION
The INA157 is a high slew rate, G = 1/2 or G = 2
difference amplifier consisting of a precision op amp
with a precision resistor network. The on-chip resis-
tors are laser trimmed for accurate gain and high
common-mode rejection. Excellent TCR tracking of
the resistors maintains gain accuracy and common-
mode rejection over temperature. The input common-
mode voltage range extends beyond the positive and
negative supply rails. It operates on
4V to
18V
supplies.
The difference amplifier is the foundation of many
commonly used circuits. The INA157 provides this
circuit function without using an expensive precision
resistor network. The INA157 is available in a SO-8
surface-mount package and is specified for operation
over the extended industrial temperature range, 40
C
to +85
C.
APPLICATIONS
q
DIFFERENTIAL INPUT AMPLIFIER
q
INSTRUMENTATION AMPLIFIER
BUILDING BLOCK
q
G = 1/2 AMPLIFIER
q
G = 2 AMPLIFIER
q
DIFFERENTIAL CURRENT RECEIVER
q
VOLTAGE-CONTROLLED CURRENT SOURCE
q
GROUND LOOP ELIMINATOR
q
CURRENT SHUNT MONITOR
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
2
3
4
In
+In
V
6k
12k
6k
12k
5
1
Sense
Ref
6
Output
7
V+
INA157
For most current data sheet and other product
information, visit www.burr-brown.com
2
INA157
SPECIFICATIONS: V
S
=
15V
At T
A
= +25
C, V
S
=
15V, R
L
= 2k
connected to ground, and reference pin connected to ground, unless otherwise noted.
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.
INA157U
INA157UA
PARAMETER
CONDITIONS
MIN
TYP
MAX
MIN
TYP
MAX
UNITS
OFFSET VOLTAGE
(1)
RTO
Initial
(1)
100
500
V
1000
V
vs Temperature
2
20
V
V
V/
C
vs Power Supply
V
S
=
4V to
18V
5
60
V
V
V/V
vs Time
0.25
V
V/mo
INPUT IMPEDANCE
(2)
Differential
24
V
k
Common-Mode
18
V
k
INPUT VOLTAGE RANGE
Common-Mode Voltage Range
Positive
V
O
= 0V
3(V+)7.5
3(V+)6
V
V
V
Negative
V
O
= 0V
3(V)+7.5
3(V)+3
V
V
V
Common-Mode Rejection Ratio
V
CM
= 37.5V to 37.5V, R
S
= 0
86
96
80
V
dB
OUTPUT VOLTAGE NOISE
(3)
RTO
f = 0.1Hz to 10Hz
1.3
V
Vp-p
f = 1kHz
26
V
nV/
Hz
GAIN
Initial
0.5
V
V/V
Error
V
O
= 10V to +10V
0.01
0.05
V
0.1
%
vs Temperature
1
10
V
V
ppm/
C
Nonlinearity
V
O
= 10V to +10V
0.0001
0.001
V
0.002
% of FS
OUTPUT
Voltage, Positive
(V+)2
(V+)1.8
V
V
V
Negative
(V)+2
(V)+1.6
V
V
V
Current Limit, Continuous to Common
60
V
mA
Capacitive Load (stable operation)
500
V
pF
FREQUENCY RESPONSE
Small-Signal Bandwidth
3dB
4
V
MHz
Slew Rate
14
V
V/
s
Settling Time: 0.1%
10V Step, C
L
= 100pF
2
V
s
0.01%
10V Step, C
L
= 100pF
3
V
s
Overload Recovery Time
50% Overdrive
3
V
s
POWER SUPPLY
Rated Voltage
15
V
V
Operating Voltage Range
4
18
V
V
V
Quiescent Current
I
O
= 0mA
2.4
2.9
V
V
mA
TEMPERATURE RANGE
Specified
40
+85
V
V
C
Operation
55
+125
V
V
C
Storage
55
+125
V
V
C
Thermal Resistance,
JA
SO-8 Surface-Mount
150
V
C/W
V
Specifications the same as INA157U.
NOTES: (1) Includes effects of amplifier's input bias and offset currents. (2) Internal resistors are ratio matched but have
20% absolute value. (3) Includes effects
of amplifier's input current noise and thermal noise contribution of resistor network.
3
INA157
PIN CONFIGURATION
TOP VIEW
SO-8
Supply Voltage, V+ to V .................................................................... 40V
Input Voltage Range ..........................................................................
80V
Output Short Circuit (to ground) ............................................. 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
NOTE: (1) Stresses above these ratings may cause permanent damage.
Exposure to absolute maximum conditions for extended periods may degrade
device reliability.
ABSOLUTE MAXIMUM RATINGS
(1)
ELECTROSTATIC
DISCHARGE SENSITIVITY
This integrated circuit can be damaged by ESD. Burr-Brown
recommends that all integrated circuits be handled with ap-
propriate 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.
PACKAGE
SPECIFIED
DRAWING
TEMPERATURE
PACKAGE
ORDERING
TRANSPORT
PRODUCT
PACKAGE
NUMBER
(1)
RANGE
MARKING
NUMBER
(2)
MEDIA
INA157U
SO-8 Surface-Mount
182
40
C to +85
C
INA157U
INA157U
Rails
"
"
"
"
"
INA157U/2K5
Tape and Reel
INA157UA
SO-8 Surface-Mount
182
40
C to +85
C
INA157UA
INA157UA
Rails
"
"
"
"
"
INA157UA/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 "INA157U/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.
PACKAGE/ORDERING INFORMATION
Ref
In
+In
V
NC
V+
Output
Sense
NC = No Connection
1
2
3
4
8
7
6
5
4
INA157
TYPICAL PERFORMANCE CURVES
At T
A
= +25
C, V
S
=
15V, and G = 1/2, unless otherwise noted.
GAIN vs FREQUENCY
Frequency (Hz)
Voltage Gain (dB)
1k
10k
100k
1M
10M
10
0
10
20
30
COMMON-MODE REJECTION RATIO vs FREQUENCY
Frequency (Hz)
Common-Mode Rejection Ratio (dB)
1k
10k
100k
1M
100
80
60
40
RTO
POWER SUPPLY REJECTION RATIO vs FREQUENCY
Frequency (Hz)
Power Supply Rejection (dB)
100
1k
10k
100k
1M
120
100
80
60
40
20
0
PSRR
RTO
+PSRR
MAXIMUM OUTPUT VOLTAGE vs FREQUENCY
Frequency (Hz)
Output Voltage (Vp-p)
100
1k
10k
100k
1M
10M
40
30
20
10
0
INPUT COMMON-MODE VOLTAGE
vs OUTPUT VOLTAGE
Output Voltage (V)
Common-Mode Voltage (V)
20
15
10
5
0
5
10
15
20
80
60
40
20
0
20
40
60
80
V
REF
= 0V
R
L
= 2k
G = 1/2
V
S
=
15V
TOTAL HARMONIC DISTORTION + NOISE
vs FREQUENCY
Frequency (Hz)
THD+Noise (%)
20
100
1k
10k
20k
0.1
0.010
0.001
0.0001
V
O
= 5Vrms
R
L
= 600
R
L
= 100k
R
L
= 2k
5
INA157
TYPICAL PERFORMANCE CURVES
(CONT)
At T
A
= +25
C, V
S
=
15V, and G = 1/2, unless otherwise noted.
QUIESCENT CURRENT vs TEMPERATURE
Temperature (
C)
Quiescent Current (mA)
75
50
25
0
25
50
75
100
125
4
3
2
1
0
SLEW RATE vs TEMPERATURE
Temperature (
C)
Slew Rate (V/
s)
75
50
25
0
25
50
75
100
+SR
125
16
14
12
10
8
SR
OUTPUT VOLTAGE NOISE SPECTRAL DENSITY
vs FREQUENCY
Frequency (Hz)
Voltage Noise (nV/
Hz)
1
10
100
1k
10k
100k
1M
10k
1k
100
10
OUTPUT NOISE VOLTAGE
vs NOISE BANDWIDTH
Frequency (Hz)
Noise Voltage (
Vrms)
1
10
100
1k
10k
100k
100
10
1
0.1
SHORT-CIRCUIT CURRENT vs TEMPERATURE
Temperature (
C)
Short-Circuit Current (mA)
75
50
25
0
25
50
75
100
125
80
60
40
20
0
20
40
60
80
+I
SC
I
SC
OUTPUT VOLTAGE SWING vs OUTPUT CURRENT
14
13
12
11
10
9
9
10
11
12
13
14
0
20
40
60
80
Output Current (mA)
Output Voltage Swing (V)
55
C
55
C
25
C
85
C
85
C
125
C
125
C
25
C
6
INA157
TYPICAL PERFORMANCE CURVES
(CONT)
At T
A
= +25
C, V
S
=
15V, and G = 1/2, unless otherwise noted.
SMALL-SIGNAL STEP RESPONSE
1
s/div
50mV/div
LARGE-SIGNAL STEP RESPONSE
1
s/div
5V/div
C
L
= 100pF
C
L
= 500pF
SMALL-SIGNAL OVERSHOOT
vs LOAD CAPACITANCE
Load Capacitance (pF)
Overshoot (%)
0
200
400
600
800
1000
1200
70
60
50
40
30
20
10
0
R
L
= 2k
100mV Step
OFFSET VOLTAGE
PRODUCTION DISTRIBUTION
Percent of Units (%)
Offset Voltage (
V)
1000
900
800
700
600
500
400
300
200
100
0
100
200
300
400
500
600
700
800
900
1000
35
30
25
20
15
10
5
0
Typical Production
Distribution of
Packaged Units.
OFFSET VOLTAGE DRIFT
PRODUCTION DISTRIBUTION
Percent of Units (%)
Offset Voltage Drift (
V/
C)
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20
25
20
15
10
5
0
Typical production distribution
of packaged units.
C
L
= 500pF
7
INA157
APPLICATIONS INFORMATION
The INA157 is a difference amplifier suitable for a wide
range of general-purpose applications. Figure 1 shows the
basic G = 1/2 configuration. The input and feedback resis-
tors can be reversed to achieve G = 2, as shown in Figure 2.
For applications requiring G = 1, the INA154 is recom-
mended.
Decoupling capacitors are strongly recommended for appli-
cations with noisy or high impedance power supplies. The
capacitors should be placed close to the device pins as
shown in Figure 1.
As shown in Figure 1, the output is referred to the reference
terminal (pin 1). A voltage applied to this pin will be
summed with the output signal. The differential input signal
is connected to pins 2 and 3. The source impedances con-
nected to the inputs must be nearly equal to assure good
common-mode rejection. A 5
mismatch in source imped-
ance will degrade the common-mode rejection of a typical
device to approximately 77dB (RTO). If the source has a
known impedance mismatch, an additional resistor in series
with the opposite input can be used to preserve good com-
mon-mode rejection.
V
3
5
6
3
1
Ref
INA157
V
O
= 1/2 (V
3
V
2
)
2
R
3
12k
R
1
12k
R
2
6k
R
4
6k
R
L
V
2
In
+In
1
F
V
4
1
F
V+
7
FIGURE 1. G = 1/2 Differential Amplifier (basic power
supply and signal connections).
FIGURE 2. G = 2 Differential Amplifier.
V
3
5
6
3
V
O
INA157
V
O
= 1/2 (V
3
V
2
)
Offset Adjustment
Range =
1mV
G = 1/2
2
R
4
6k
V
2
20
250k
10
100k
+15V
15V
1
R
3
12k
R
1
12k
R
2
6k
FIGURE 3. Offset Adjustment.
OPERATING VOLTAGE
The INA157 operates from
4V to
18V supplies with
excellent performance. Most behavior remains unchanged
throughout the full operating voltage range. Parameters
which vary significantly with operating voltage are shown in
the Typical Performance Curves.
INPUT VOLTAGE RANGE
The INA157 can accurately measure differential signals
that are above the positive or negative power supply rail. In
a gain of 1/2, the linear common-mode range extends from
3(V+) 7.5V to 3(V) +7.5V. See the Typical Perfor-
mance Curve, "Input Common-Mode Range vs Output
Voltage."
OFFSET VOLTAGE TRIM
The INA157 is laser trimmed for low offset voltage and
drift. Most applications require no external offset adjust-
ment. Figure 3 shows an optional circuit for trimming the
output offset voltage. The output is referred to the output
reference terminal (pin 1), which is normally grounded. A
voltage applied to the Ref terminal will be summed with the
output signal. This can be used to null offset voltage as
shown in Figure 3. The source impedance of a signal
applied to the Ref terminal should be less than 10
to
maintain good common-mode rejection.
V
3
2
6
1
INA157
V
O
= 2 (V
3
V
2
)
5
R
4
6k
R
3
12k
R
2
6k
R
1
12k
V
2
In
+In
3
Ref
R
L
8
INA157
The INA157 can be combined with op amps to form a complete instru-
mentation amplifier with specialized performance characteristics. Burr-
Brown offers many complete high performance IAs. Products with related
performances are shown at the right.
SIMILIAR COMPLETE
A
1
, A
2
FEATURE
BURR-BROWN IAs
OPA227
Low Noise
INA103
OPA129
Ultra Low Bias Current (fA)
INA116
OPA277
Low Offset Drift, Low Noise
INA114, INA128
OPA2134
FET Input (pA)
INA111, INA121
FIGURE 6. Boosting Output Current.
FIGURE 5. Precision Instrumentation Amplifier.
FIGURE 4. Precision Summing Amplifier.
V
1
V
2
5
6
1
3
V
0
= 2V
1
+ V
2
INA157
2
6k
6k
12k
12k
5
6
1
3
INA157
2
V
1
V
O
A
2
A
1
R
2
R
2
R
1
In
V
2
+In
V
O
= (1 + 2R
2
/R
1
) (V
2
V
1
)
5
6
1
INA157
BUF634
2
3
V
O
R
L
In
+In
(Low I
Q
mode)
BUF634 inside feedback
loop contributes no error.
The difference amplifier is a highly versatile building
block that is useful in a wide variety of applications. See
the INA105 data sheet for additional applications ideas,
including:
Current Receiver with Compliance to Rails
10V Precision Voltage Reference
5V Precision Voltage Reference
Precision Average Value Amplifier
Precision Bipolar Offsetting
Precision Summing Amplifier with Gain
Instrumentation Amplifier Guard Drive Generator
Precision Summing Instrumentation Amplifier
Precision Absolute Value Buffer
Precision Voltage-to-Current Converter with Differential
Inputs
Differential Input Voltage-to-Current Converter for Low
I
OUT
Isolating Current Source
Differential Output Difference Amplifier
Isolating Current Source with Buffering Amplifier for
Greater Accuracy
Window Comparator with Window Span and Window
Center Inputs
Precision Voltage-Controlled Current Source with Buff-
ered Differential Inputs and Gain
Digitally Controlled Gain of
1 Amplifier
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