INA

125
®
INA125
INA1
25

INSTRUMENTATION AMPLIFIER
With Precision Voltage Reference

FEATURES APPLICATIONS
● LOW QUIESCENT CURRENT: 460µA ● PRESSURE AND TEMPERATURE BRIDGE
● PRECISION VOLTAGE REFERENCE: AMPLIFIERS
1.24V, 2.5V, 5V or 10V ● INDUSTRIAL PROCESS CONTROL
● SLEEP MODE ● FACTORY AUTOMATION
● LOW OFFSET VOLTAGE: 250µV max ● MULTI-CHANNEL DATA ACQUISITION
● LOW OFFSET DRIFT: 2µV/°C max ● BATTERY OPERATED SYSTEMS
● LOW INPUT BIAS CURRENT: 20nA max ● GENERAL PURPOSE INSTRUMENTATION
● HIGH CMR: 100dB min
V+ SLEEP
● LOW NOISE: 38nV/√ Hz at f = 1kHz
● INPUT PROTECTION TO ±40V 1 2
INA125
● WIDE SUPPLY RANGE VREFCOM 12

Single Supply: 2.7V to 36V R

Dual Supply: ±1.35V to ±18V 13
VREFBG
● 16-PIN DIP AND SO-16 SOIC PACKAGES
R
14
VREF2.5

DESCRIPTION 2R
15
VREF5
The INA125 is a low power, high accuracy instrumen-
tation amplifier with a precision voltage reference. It 4R
VREF10 16
provides complete bridge excitation and precision dif-
ferential-input amplification on a single integrated 4 Ref
Amp Bandgap
circuit. 10V
VREFOut
VREF
A single external resistor sets any gain from 4 to
+
VIN
10,000. The INA125 is laser-trimmed for low offset
6 10
voltage (250µV), low offset drift (2µV/°C), and high A1 VO
common-mode rejection (100dB at G = 100). It oper- 9
ates on single (+2.7V to +36V) or dual (±1.35V to 30kΩ
11
±18V) supplies. 10kΩ Sense
RG
The voltage reference is externally adjustable with pin- 10kΩ
selectable voltages of 2.5V, 5V, or 10V, allowing use + –) G
VO = (VIN – VIN
with a variety of transducers. The reference voltage is 8 G = 4 + 60kΩ
accurate to ±0.5% (max) with ±35ppm/°C drift (max). A2
RG
7
Sleep mode allows shutdown and duty cycle operation –
VIN
30kΩ
to save power. IAREF
5
The INA125 is available in 16-pin plastic DIP and 3
SO-16 surface-mount packages and is specified for
the –40°C to +85°C industrial temperature range. V–

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/ • FAXLine: (800) 548-6133 (US/Canada Only) • Cable: BBRCORP • Telex: 066-6491 • FAX: (520) 889-1510 • Immediate Product Info: (800) 548-6132

©1997 Burr-Brown Corporation PDS-1361B Printed in U.S.A., February, 1998

SBOS060
SPECIFICATIONS: VS = ±15V
At TA = +25°C, VS = ±15V, IA common = 0V, VREF common = 0V, and RL = 10kΩ, unless otherwise noted.

INA125P, U INA125PA, UA

PARAMETER CONDITIONS MIN TYP MAX MIN TYP MAX UNITS

INPUT
Offset Voltage, RTI
Initial ±50 ±250 ✻ ±500 µV
vs Temperature ±0.25 ±2 ✻ ±5 µV/°C
vs Power Supply VS = ±1.35V to ±18V, G = 4 ±3 ±20 ✻ ±50 µV/V
Long-Term Stability ±0.2 ✻ µV/mo
Impedance, Differential 1011 || 2 ✻ Ω || pF
Common-Mode 1011 || 9 ✻ Ω || pF
Safe Input Voltage ±40 ✻ V
Input Voltage Range See Text ✻
Common-Mode Rejection VCM = –10.7V to +10.2V
G=4 78 84 72 ✻ dB
G = 10 86 94 80 ✻ dB
G = 100 100 114 90 ✻ dB
G = 500 100 114 90 ✻ dB
BIAS CURRENT VCM = 0V 10 25 ✻ 50 nA
vs Temperature ±60 ✻ pA/°C
Offset Current ±0.5 ±2.5 ✻ ±5 nA
vs Temperature ±0.5 ✻ pA/°C
NOISE, RTI RS = 0Ω
Voltage Noise, f = 10Hz 40 ✻ nV/√Hz
f = 100Hz 38 ✻ nV/√Hz
f = 1kHz 38 ✻ nV/√Hz
f = 0.1Hz to 10Hz 0.8 ✻ µVp-p
Current Noise, f = 10Hz 170 ✻ fA/√Hz
f = 1kHz 56 ✻ fA/√Hz
f = 0.1Hz to 10Hz 5 ✻ pAp-p
GAIN
Gain Equation 4 + 60kΩ/RG ✻ V/V
Range of Gain 4 10,000 ✻ ✻ V/V
Gain Error VO = –14V to +13.3V
G=4 ±0.01 ±0.075 ✻ ±0.1 %
G = 10 ±0.03 ±0.3 ✻ ±0.5 %
G = 100 ±0.05 ±0.5 ✻ ±1 %
G = 500 ±0.1 ✻ %
Gain vs Temperature
G=4 ±1 ±15 ✻ ✻ ppm/°C
G > 4(1) ±25 ±100 ✻ ✻ ppm/°C
Nonlinearity VO = –14V to +13.3V
G=4 ±0.0004 ±0.002 ✻ ±0.004 % of FS
G = 10 ±0.0004 ±0.002 ✻ ±0.004 % of FS
G = 100 ±0.001 ±0.01 ✻ ✻ % of FS
G = 500 ±0.002 ✻ % of FS
OUTPUT
Voltage: Positive (V+)–1.7 (V+)–0.9 ✻ ✻ V
Negative (V–)+1 (V–)+0.4 ✻ ✻ V
Load Capacitance Stability 1000 ✻ pF
Short-Circuit Current –9/+12 ✻ mA
VOLTAGE REFERENCE VREF = +2.5V, +5V, +10V
Accuracy IL = 0 ±0.15 ±0.5 ✻ ±1 %
vs Temperature IL = 0 ±18 ±35 ✻ ±100 ppm/°C
vs Power Supply, V+ V+ = (VREF + 1.25V) to +36V ±20 ±50 ✻ ±100 ppm/V
vs Load IL = 0 to 5mA 3 75 ✻ ✻ ppm/mA
Dropout Voltage, (V+) – VREF(2) Ref Load = 2kΩ 1.25 1 ✻ ✻ V
Bandgap Voltage Reference 1.24 ✻ V
Accuracy IL = 0 ±0.5 ✻ %
vs Temperature IL = 0 ±18 ✻ ppm/°C

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.

INA125 2
SPECIFICATIONS: VS = ±15V (CONT)
At TA = +25°C, VS = ±15V, IA common = 0V, VREF common = 0V, and RL = 10kΩ, unless otherwise noted.

INA125P, U INA125PA, UA

PARAMETER CONDITIONS MIN TYP MAX MIN TYP MAX UNITS

FREQUENCY RESPONSE
Bandwidth, –3dB G=4 150 ✻ kHz
G = 10 45 ✻ kHz
G = 100 4.5 ✻ kHz
G = 500 0.9 ✻ kHz
Slew Rate G = 4, 10V Step 0.2 ✻ V/µs
Settling Time, 0.01% G = 4, 10V Step 60 ✻ µs
G = 10, 10V Step 83 ✻ µs
G = 100, 10V Step 375 ✻ µs
G = 500, 10V Step 1700 ✻ µs
Overload Recovery 50% Overdrive 5 ✻ µs
POWER SUPPLY
Specified Operating Voltage ±15 ✻ V
Specified Voltage Range ±1.35 ±18 ✻ ✻ V
Quiescent Current, Positive IO = IREF = 0mA 460 525 ✻ ✻ µA
Negative IO = IREF = 0mA –280 –325 ✻ ✻ µA
Reference Ground Current(3) 180 ✻ µA
Sleep Current (VSLEEP ≤ 100mV) RL = 10kΩ, Ref Load = 2kΩ ±1 ±25 ✻ ✻ µA
SLEEP MODE PIN(4)
VIH (Logic high input voltage) +2.7 V+ ✻ ✻ V
VIL (Logic low input voltage) 0 +0.1 ✻ ✻ V
IIH (Logic high input current) 15 ✻ µA
IIL (Logic low input current) 0 ✻ µA
Wake-up Time(5) 150 ✻ µs
TEMPERATURE RANGE
Specification Range –40 +85 ✻ ✻ °C
Operation Range –55 +125 ✻ ✻ °C
Storage Range –55 +125 ✻ ✻ °C
Thermal Resistance, θJA
16-Pin DIP 80 ✻ °C/W
SO-16 Surface-Mount 100 ✻ °C/W
✻ Specification same as INA125P, U.
NOTES: (1) Temperature coefficient of the "Internal Resistor" in the gain equation. Does not include TCR of gain-setting resistor, RG. (2) Dropout voltage is the
positive supply voltage minus the reference voltage that produces a 1% decrease in reference voltage. (3) VREFCOM pin. (4) Voltage measured with respect to
Reference Common. Logic low input selects Sleep mode. (5) IA and Reference, see Typical Performance Curves.

SPECIFICATIONS: VS = +5V
At TA = +25°C, VS = +5V, IA common at VS /2, VREF common = VS /2, VCM = VS/2, and RL = 10kΩ to VS/2, unless otherwise noted.

INA125P, U INA125PA, UA

PARAMETER CONDITIONS MIN TYP MAX MIN TYP MAX UNITS

INPUT
Offset Voltage, RTI
Initial ±75 ±500 ✻ ±750 µV
vs Temperature ±0.25 ✻ µV/°C
vs Power Supply VS = +2.7V to +36V 3 20 ✻ 50 µV/V
Input Voltage Range See Text ✻
Common-Mode Rejection VCM = +1.1V to +3.6V
G=4 78 84 72 ✻ dB
G = 10 86 94 80 ✻ dB
G = 100 100 114 90 ✻ dB
G = 500 100 114 90 ✻ dB
GAIN
Gain Error VO = +0.3V to +3.8V
G=4 ±0.01 ✻ %
OUTPUT
Voltage, Positive (V+)–1.2 (V+)–0.8 ✻ ✻ V
Negative (V–)+0.3 (V–)+0.15 ✻ ✻ V
POWER SUPPLY
Specified Operating Voltage +5 ✻ V
Operating Voltage Range +2.7 +36 ✻ ✻ V
Quiescent Current IO = IREF = 0mA 460 525 ✻ ✻ µA
Sleep Current (VSLEEP ≤ 100mV) RL = 10kΩ, Ref Load = 2kΩ ±1 ±25 ✻ ✻ µA

✻ Specification same as INA125P, U.

®

3 INA125
PIN CONFIGURATION ABSOLUTE MAXIMUM RATINGS(1)
Top View 16-Pin DIP, SO-16 Power Supply Voltage, V+ to V– ........................................................ 36V
Input Signal Voltage .......................................................................... ±40V
Output Short Circuit ................................................................. Continuous
Operating Temperature ................................................. –55°C to +125°C
V+ 1 16 VREF10
Storage Temperature ..................................................... –55°C to +125°C
SLEEP 2 15 VREF5 Lead Temperature (soldering, 10s) ............................................... +300°C

V– 3 14 VREF2.5 NOTE: Stresses above these ratings may cause permanent damage.

VREFOUT 4 13 VREFBG

IAREF 5 12 VREFCOM
PACKAGE INFORMATION
+ PACKAGE DRAWING
VIN 6 11 Sense
PRODUCT PACKAGE NUMBER(1)
–
VIN 7 10 VO INA125PA 16-Pin Plastic DIP 180
INA125P 16-Pin Plastic DIP 180
RG 8 9 RG
INA125UA SO-16 Surface-Mount 265
INA125U SO-16 Surface-Mount 265
NOTES: (1) For detailed drawing and dimension table, please see end of data
sheet, or Appendix C of Burr-Brown IC Data Book.

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.

INA125 4
TYPICAL PERFORMANCE CURVES
At TA = +25°C and VS = ±15V, unless otherwise noted.

GAIN vs FREQUENCY COMMON-MODE REJECTION vs FREQUENCY

60 120
G = 500 G = 100, 500

Common-Mode Rejection (dB)

50 100

G = 100
40 80
Gain (dB)

G = 10
30 60
G = 500
G=4
G = 10
20 40 G = 100
G=4
10 20

0 0
1 10 100 1k 10k 100k 1M 1 10 100 1k 10k 100k 1M
Frequency (Hz) Frequency (Hz)

POSITIVE POWER SUPPLY REJECTION NEGATIVE POWER SUPPLY REJECTION

vs FREQUENCY vs FREQUENCY
140 120

120
Power Supply Rejection (dB)

100
Power Supply Rejection (dB)

G = 500
100 80 G = 100
G = 100 G = 500
80 60
G=4
60 G = 10 40
G = 10
40 20
G=4
20 0
1 10 100 1k 10k 100k 1M 1 10 100 1k 10k 100k 1M
Frequency (Hz) Frequency (Hz)

INPUT COMMON-MODE VOLTAGE INPUT COMMON-MODE VOLTAGE

vs OUTPUT VOLTAGE, VS = ±15V vs OUTPUT VOLTAGE, VS = ±5V
15 5
text
tput swing—see IAREF = 0V
Limited by A2 ou text
Input Common-Mode Voltage (V)

4 tput swing—see
Input Common-Mode Voltage (V)

10 Limited by A2 ou
3

5 2 VS = +5V
+15V
+
VD/2 1
–
0 + VO 0
VD/2
+ – IAREF
–1
–5 VCM
–15V –2 VS = ±5V

–10 –3
text
tput swing—see –4 tput swing—see
text
Limited by A2 ou Limited by A2 ou
–15 –5
–15 –10 –5 0 5 10 15 –5 –4 –3 –2 –1 0 1 2 3 4 5
Output Voltage (V) Output Voltage (V)

5 INA125
TYPICAL PERFORMANCE CURVES (CONT)
At TA = +25°C and VS = ±15V, unless otherwise noted.

INPUT-REFERRED VOLTAGE AND CURRENT NOISE

vs FREQUENCY SETTLING TIME vs GAIN
1k 1k 10k
Input-Referred Voltage Noise (nV/√Hz)

Input Bias Current Noise (fA/√Hz)

Current Noise 0.01%

Settling Time (µs)

100 100 1k

Voltage Noise 0.1%

10 10 100

1 1 10
1 10 100 1k 10k 100k 1 10 100 1k
Frequency (Hz) Gain (V/V)

INPUT-REFERRED OFFSET VOLTAGE QUIESCENT CURRENT AND SLEEP CURRENT

vs SLEEP TURN-ON TIME vs TEMPERATURE
100 550
80 500
Quiescent and Sleep Current (µA)

450
Offset Voltage Change (µV)

60 G = 100
400 +IQ
40
350
20 300
0 250 ±ISLEEP
200 –IQ
–20
150 VSLEEP = 100mV
–40 +ISLEEP
100
–60 VSLEEP = 0V
50
–80 0 –ISLEEP
–100 –50
0 50 100 150 200 250 –75 –50 –25 0 25 50 75 100 125
Time From Turn-On (µs) Temperature (°C)

INPUT BIAS AND OFFSET CURRENT

SLEW RATE vs TEMPERATURE vs TEMPERATURE
0.30 16
Input Bias and Offset Current (nA)

14
0.25
12
Slew Rate (V/µs)

0.20
10

0.15 8
IB
6
0.10
4
0.05 IOS
2

0 0
–75 –50 –25 0 25 50 75 100 125 –75 –50 –25 0 25 50 75 100 125
Temperature (°C) Temperature (°C)

INA125 6
 TYPICAL PERFORMANCE CURVES (CONT)
At TA = +25°C and VS = ±15V, unless otherwise noted.

SMALL-SIGNAL RESPONSE LARGE-SIGNAL RESPONSE

G=4 G=4
200mV/div

5V/div
G = 100 G = 100

100µs/div 100µs/div

INPUT BIAS CURRENT

INPUT-REFERRED NOISE, 0.1Hz to 10Hz vs INPUT OVERLOAD VOLTAGE
200
160
All Gains
120
Input Bias Current (µA)

80
40
200nV/div

0
–40
–80
–120
–160
–200
1µs/div –40 0 40
Overload Voltage (V)

OUTPUT VOLTAGE SWING

vs OUTPUT CURRENT DELTA VOS vs REFERENCE CURRENT
V+ 25
(V+)–1 +75°C
(V+)–2 20
+25°C
(V+)–3 +125°C Sinking
Delta VOS, RTI (µV)
Output Voltage (V)

(V+)–4 15
–55°C
(V+)–5
10
(V–)+5
(V–)+4 +75°C 5
–55°C Sourcing
(V–)+3
(V–)+2 +125°C 0
(V–)+1 +25°C
V– –5
0 ±2 ±4 ±6 ±8 ±10 –8 –6 –4 –2 0 2 4 6 8
Output Current (mA) Reference Current (mA)

7 INA125
TYPICAL PERFORMANCE CURVES (CONT)
At TA = +25°C and VS = ±15V, unless otherwise noted.

INPUT-REFERRED OFFSET VOLTAGE INPUT-REFERRED OFFSET VOLTAGE

PRODUCTION DISTRIBUTION, VS = ±15V PRODUCTION DISTRIBUTION, VS = +5V
30 35
Typical production Typical production
25 distribution of 30 distribution of
packaged units. packaged units.
Percent of Amplifiers (%)

Percent of Amplifiers (%)

25
20
20
15
15
10
10
0.1% 0.02% 0.1% 0.1%
0.02% 0.05%
5 5
0.02% 0.1%

0 0
–500
–450
–400
–350
–300
–250
–200
–150
–100
–50
0
50
100
150
200
250
300
350
400
450
500

–750
–675
–600
–525
–450
–375
–300
–225
–150
–75
0
75
150
225
300
375
450
525
600
675
750
Input-Referred Offset Voltage (µV) Input-Referred Offset Voltage (µV)

INPUT-REFERRED OFFSET VOLTAGE DRIFT VOLTAGE REFERENCE DRIFT

PRODUCTION DISTRIBUTION PRODUCTION DISTRIBUTION
90 100
Typical production Typical production
80 90
distribution of packaged units. distribution of packaged units.
80
Percent of Amplifiers (%)

70
Percent of Amplifiers (%)

70
60
VS = ±15V or +5V 60
50
50
40
40
30 30
0.3% 0.2%
20 20
0.05%
10 10

0 0
10

20

30

40

50

60

70

80

90

100
±0.25
±0.50
±0.75
±1.00
±1.25
±1.50
±1.75
±2.00
±2.25
±2.50
±2.75
±3.00
±3.25
±3.50
±3.75
±4.00

Voltage Reference Drift (ppm/°C)

Input-Referred Offset Voltage Drift (µV/°C)

REFERENCE VOLTAGE DEVIATION

REFERENCE TURN-ON SETTLING TIME vs TEMPERATURE
15 50
Reference Voltage Deviation (ppm)

12 VREF = VBG, 2.5V, 5V, or 10V

9 0
Reference Error (%)

6
4 –50
0
–3 –100
–6 VREF = 10V

–9 VREF = 5V –150
–12 VREF = 2.5V
–15 –200
0 10 20 30 40 50 –75 –50 –25 0 25 50 75 100 125
Time From Power Supply Turn-On (µs) Temperature (°C)

INA125 8
TYPICAL PERFORMANCE CURVES (CONT)
At TA = +25°C and V S = ±15V, unless otherwise noted.

0.1Hz to 10Hz REFERENCE NOISE REFERENCE TRANSIENT RESPONSE

VREF = 2.5V, CL = 100pF VREF = 2.5V, CL = 100pF

1mA/div
+1mA

0mA

–1mA
2µV/div

Reference
Output
50mV/div
1µs/div 10µs/div

POSITIVE REFERENCE AC LINE REJECTION NEGATIVE REFERENCE AC LINE REJECTION

vs FREQUENCY vs FREQUENCY
120 120
VREF = 2.5V VREF = 2.5V
VREF = 5V Negative AC Line Rejection (dB)
Positive AC Line Rejection (dB)

100 100

80 VREF = 5V
80
VREF = 10V VREF = 10V
60 C = 0.01µF 60

C = 0.1µF
40 40

20 Capacitor connected between 20

VREFOUT and VREFCOM.

0 0
1 10 100 1k 10k 100k 1M 1 10 100 1k 10k 100k 1M
Frequency (Hz) Frequency (Hz)

9 INA125
APPLICATION INFORMATION For example, in Figure 1 VREFOUT is connected to VREF10
thus supplying 10V to the bridge. It is recommended that
Figure 1 shows the basic connections required for operation VREFOUT be connected to one of the reference voltage pins
of the INA125. Applications with noisy or high impedance even when the reference is not being utilized to avoid
power supplies may require decoupling capacitors close to saturating the reference amplifier. Driving the SLEEP pin
the device pins as shown. LOW puts the INA125 in a shutdown mode.
The output is referred to the instrumentation amplifier refer-
ence (IAREF) terminal which is normally grounded. This SETTING THE GAIN
must be a low impedance connection to assure good com-
Gain of the INA125 is set by connecting a single external
mon-mode rejection. A resistance of 12Ω in series with the
resistor, RG, between pins 8 and 9:
IAREF pin will cause a typical device to degrade to approxi-
mately 80dB CMR (G = 4). 60kΩ (1)
G =4+
Connecting VREFOUT (pin 4) to one of the four available RG
reference voltage pins (VREFBG, VREF2.5, VREF5, or VREF10) Commonly used gains and RG resistor values are shown in
provides an accurate voltage source for bridge applications. Figure 1.

V+
SLEEP(1)
0.1µF

1 2
INA125
VREFCOM 12
DESIRED GAIN RG NEAREST 1%
(V/V) (Ω) RG VALUE (Ω)
R(2)
4 NC NC
5 60k 60.4k 13
VREFBG
10 10k 10k
20 3750 3740 R
50 1304 1300 14
100 625 619 VREF2.5
200 306 309
500 121 121 2R
1000 60 60.4 15
2000 30 30.1 VREF5
10000 6 6.04
4R
NC: No Connection. VREF10 16

4 Ref
VREFOut Amp Bandgap + – V –) G
10V VO = (VIN IN
VREF
G = 4 + 60kΩ
RG
+
VIN
6 10
A1

9
30kΩ
11
Sense +
10kΩ
RG

10kΩ

Load
8 VO

A2
7
–
VIN 30kΩ IAREF –
5
NOTE: (1) SLEEP pin should be connected 3
to V+ if shutdown function is not being used. 0.1µF
(2) Nominal value of R is 21kΩ, ±25%.

V–

FIGURE 1. Basic Connections.

®

INA125 10
The 60kΩ term in equation 1 comes from the internal metal INPUT COMMON-MODE RANGE
film resistors which are laser trimmed to accurate absolute The input common-mode range of the INA125 is shown in
values. The accuracy and temperature coefficient of these the typical performance curves. The common-mode range is
resistors are included in the gain accuracy and drift specifi- limited on the negative side by the output voltage swing of
cations of the INA125. A2, an internal circuit node that cannot be measured on an
The stability and temperature drift of the external gain external pin. The output voltage of A2 can be expressed as:
setting resistor, RG, also affects gain. RG’s contribution to V = 1.3V – – (V + – V – ) (10kΩ/R )
02 IN IN IN G
gain accuracy and drift can be directly inferred from the gain
equation (1). Low resistor values required for high gain can (voltages referred to IAREF terminal, pin 5)
make wiring resistance important. Sockets add to the wiring The internal op amp A2 is identical to A1. Its output swing
resistance, which will contribute additional gain error (pos- is limited to approximately 0.8V from the positive supply
sibly an unstable gain error) in gains of approximately 100 and 0.25V from the negative supply. When the input com-
or greater. mon-mode range is exceeded (A2’s output is saturated), A1
can still be in linear operation, responding to changes in the
OFFSET TRIMMING non-inverting input voltage. The output voltage, however,
will be invalid.
The INA125 is laser trimmed for low offset voltage and
offset voltage drift. Most applications require no external
offset adjustment. Figure 2 shows an optional circuit for PRECISION VOLTAGE REFERENCE
trimming the output offset voltage. The voltage applied to The on-board precision voltage reference provides an accu-
the IAREF terminal is added to the output signal. The op amp rate voltage source for bridge and other transducer applica-
buffer is used to provide low impedance at the IAREF tions or ratiometric conversion with analog-to-digital con-
terminal to preserve good common-mode rejection. verters. A reference output of 2.5V, 5V or 10V is available
by connecting VREFOUT (pin 4) to one of the VREF pins
(VREF2.5, VREF5, or VREF10). Reference voltages are laser-
–
VIN
V+
trimmed for low inital error and low temperature drift.
RG INA125 VO
Connecting VREFOUT to VREFBG (pin 13) produces the
100µA bandgap reference voltage (1.24V ±0.5%) at the reference
IAREF 1/2 REF200
V+
IN output.
Positive supply voltage must be 1.25V above the desired
OPA237 10kΩ 100Ω reference voltage. For example, with V+ = 2.7V, only the
±10mV 1.24V reference (VREFBG) can be used. If using dual sup-
Adjustment Range plies VREFCOM can be connected to V–, increasing the
100Ω

100µA Microphone,
1/2 REF200 Hydrophone INA125
etc.
V–

FIGURE 2. Optional Trimming of Output Offset Voltage. 47kΩ 47kΩ

INPUT BIAS CURRENT RETURN

The input impedance of the INA125 is extremely high—
approximately 1011Ω. However, a path must be provided for
the input bias current of both inputs. This input bias current Thermocouple INA125
flows out of the device and is approximately 10nA. High
input impedance means that this input bias current changes
very little with varying input voltage. 10kΩ

Input circuitry must provide a path for this input bias current
for proper operation. Figure 3 shows various provisions for
an input bias current path. Without a bias current path, the
inputs will float to a potential which exceeds the common- INA125
mode range, and the input amplifiers will saturate.
If the differential source resistance is low, the bias current
return path can be connected to one input (see the thermo-
Center-tap provides
couple example in Figure 3). With higher source impedance, bias current return.
using two equal resistors provides a balanced input with
possible advantages of lower input offset voltage due to bias FIGURE 3. Providing an Input Common-Mode Current Path.
current and better high frequency common-mode rejection. ®

11 INA125
amount of supply voltage headroom available to the refer- A transition region exists when VSLEEP is between 400mV
ence. Approximately 180µA flows out of the VREFCOM and 2.7V (with respect to VREFCOM) where the output is
terminal, therefore, it is recommended that it be connected unpredictable. Operation in this region is not recommended.
through a low impedance path to sensor common to avoid The INA125 achieves high accuracy quickly following wake-
possible ground loop problems. up (VSLEEP ≥ 2.7V). See the typical performance curve
Reference noise is proportional to the reference voltage “Input-Referred Offset Voltage vs Sleep Turn-on Time.” If
selected. With VREF = 2.5V, 0.1Hz to 10Hz peak-to-peak shutdown is not being used, connect the SLEEP pin to V+.
noise is approximately 9µVp-p. Noise increases to 36µVp-p
for the 10V reference. Output drive capability of the voltage LOW VOLTAGE OPERATION
reference is improved by connecting a transistor as shown in The INA125 can be operated on power supplies as low as
Figure 4. The external transistor also serves to remove power ±1.35V. Performance remains excellent with power sup-
from the INA125. plies ranging from ±1.35V to ±18V. Most parameters vary
Internal resistors that set the voltage reference output are only slightly throughout this supply voltage range—see
ratio-trimmed for accurate output voltages (±0.5% max). The typical performance curves. Operation at very low supply
absolute resistance values, however, may vary ±25%. Adjust- voltage requires careful attention to ensure that the com-
ment of the reference output voltage with an external resistor mon-mode voltage remains within its linear range. See
is not recommended because the required resistor value is “Input Common-Mode Voltage Range.” As previously men-
uncertain. tioned, when using the on-board reference with low supply
voltages, it may be necessary to connect VREFCOM to V– to
ensure VS – VREF ≥ 1.25V.

INA125
VREFCOM 12 SINGLE SUPPLY OPERATION
The INA125 can be used on single power supplies of +2.7V
to +36V. Figure 5 shows a basic single supply circuit. The
13
VREFBG IAREF, VREFCOM, and V– terminals are connected to ground.
Zero differential input voltage will demand an output volt-
14 age of 0V (ground). When the load is referred to ground as
VREF2.5
shown, actual output voltage swing is limited to approxi-
mately 150mV above ground. The typical performance curve
15 “Output Voltage Swing vs Output Current” shows how the
VREF5
output swing varies with output current.
VREF10 16 With single supply operation, careful attention should be
paid to input common-mode range, output voltage swing of
V+ both op amps, and the voltage applied to the IAREF terminal.
VIN+ and VIN– must both be 1V above ground for linear
operation. You cannot, for instance, connect the inverting
4 Ref
TIP29C input to ground and measure a voltage connected to the non-
VREFOut Amp Bandgap
VREF
inverting input.
10V
to load
(transducer)

+3V +3V
FIGURE 4. Reference Current Boost.
1.5V – ∆V

SHUTDOWN RG VO
INA125
1000Ω 12
The INA125 has a shutdown option. When the SLEEP pin 5 RL
is LOW (100mV or less), the supply current drops to 1.5V + ∆V 3
approximately 1µA and output impedance becomes approxi-
mately 80kΩ. Best performance is achieved with CMOS
logic. To maintain low sleep current at high temperatures,
VSLEEP should be as close to 0V as possible. This should not
be a problem if using CMOS logic unless the CMOS gate is FIGURE 5. Single Supply Bridge Amplifier.
driving other currents. Refer to the typical performance
curve, “Sleep Current vs Temperature.”

INA125 12
INPUT PROTECTION
The inputs of the INA125 are individually protected for excessive noise. If the input is overloaded, the protection
voltage up to ±40V. For example, a condition of –40V on circuitry limits the input current to a safe value of approxi-
one input and +40V on the other input will not cause mately 120µA to 190µA. The typical performance curve
damage. Internal circuitry on each input provides low series “Input Bias Current vs Input Overload Voltage” shows this
impedance under normal signal conditions. To provide input current limit behavior. The inputs are protected even if
equivalent protection, series input resistors would contribute the power supplies are disconnected or turned off.

+5V SLEEP

1 2
INA125
VREFCOM 12

13
VREFBG

VREF2.5 14

15
VREF5

16
VREF10
Ref
4 Amp Bandgap
2.5V VREF

+
VIN
6 10
A1

9
30kΩ
11
Sense +
10kΩ
RG

10kΩ

60kΩ
Load VO = +2.5V + [(VIN
+ –
– VIN ) (4 + )]
8 RG

A2
7
–
VIN
30kΩ IAREF –
5
3
2.5V(1)
(Psuedoground)

NOTE: (1) “Psuedoground” is at +2.5V above actual ground.

This provides a precision reference voltage for succeeding
single-supply op amp stages.

FIGURE 6. Psuedoground Bridge Measurement, 5V Single Supply.

13 INA125
 PACKAGE OPTION ADDENDUM

www.ti.com 7-Oct-2021

PACKAGING INFORMATION

Orderable Device Status Package Type Package Pins Package Eco Plan Lead finish/ MSL Peak Temp Op Temp (°C) Device Marking Samples
(1) Drawing Qty (2) Ball material (3) (4/5)
(6)

INA125P ACTIVE PDIP N 16 25 RoHS & Green Call TI N / A for Pkg Type -40 to 85 INA125P

INA125PA ACTIVE PDIP N 16 25 RoHS & Green Call TI N / A for Pkg Type INA125P
A
INA125PAG4 ACTIVE PDIP N 16 25 RoHS & Green Call TI N / A for Pkg Type INA125P
A
INA125U ACTIVE SOIC D 16 40 RoHS & Green Call TI Level-3-260C-168 HR INA125U
A
INA125U/2K5 ACTIVE SOIC D 16 2500 RoHS & Green Call TI Level-3-260C-168 HR INA125U
A
INA125UA ACTIVE SOIC D 16 40 RoHS & Green Call TI Level-3-260C-168 HR INA125U
A
INA125UA/2K5 ACTIVE SOIC D 16 2500 RoHS & Green Call TI Level-3-260C-168 HR INA125U
A

(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)
RoHS: TI defines "RoHS" to mean semiconductor products that are compliant with the current EU RoHS requirements for all 10 RoHS substances, including the requirement that RoHS substance
do not exceed 0.1% by weight in homogeneous materials. Where designed to be soldered at high temperatures, "RoHS" products are suitable for use in specified lead-free processes. TI may
reference these types of products as "Pb-Free".
RoHS Exempt: TI defines "RoHS Exempt" to mean products that contain lead but are compliant with EU RoHS pursuant to a specific EU RoHS exemption.
Green: TI defines "Green" to mean the content of Chlorine (Cl) and Bromine (Br) based flame retardants meet JS709B low halogen requirements of <=1000ppm threshold. Antimony trioxide based
flame retardants must also meet the <=1000ppm threshold requirement.

(3)
MSL, Peak Temp. - The Moisture Sensitivity Level rating according to the JEDEC industry standard classifications, and peak solder temperature.

(4)
There may be additional marking, which relates to the logo, the lot trace code information, or the environmental category on the device.

(5)
Multiple Device Markings will be inside parentheses. Only one Device Marking contained in parentheses and separated by a "~" will appear on a device. If a line is indented then it is a continuation
of the previous line and the two combined represent the entire Device Marking for that device.

Addendum-Page 1
 PACKAGE OPTION ADDENDUM

www.ti.com 7-Oct-2021

(6)
Lead finish/Ball material - Orderable Devices may have multiple material finish options. Finish options are separated by a vertical ruled line. Lead finish/Ball material values may wrap to two
lines if the finish value exceeds the maximum column width.

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.

Addendum-Page 2
 PACKAGE MATERIALS INFORMATION

www.ti.com 3-Jun-2022

TAPE AND REEL INFORMATION

REEL DIMENSIONS TAPE DIMENSIONS

K0 P1

B0 W
Reel
Diameter
Cavity A0
A0 Dimension designed to accommodate the component width
B0 Dimension designed to accommodate the component length
K0 Dimension designed to accommodate the component thickness
W Overall width of the carrier tape
P1 Pitch between successive cavity centers

Reel Width (W1)

QUADRANT ASSIGNMENTS FOR PIN 1 ORIENTATION IN TAPE

Sprocket Holes

Q1 Q2 Q1 Q2

Q3 Q4 Q3 Q4 User Direction of Feed

Pocket Quadrants

*All dimensions are nominal

Device Package Package Pins SPQ Reel Reel A0 B0 K0 P1 W Pin1
Type Drawing Diameter Width (mm) (mm) (mm) (mm) (mm) Quadrant
(mm) W1 (mm)
INA125U/2K5 SOIC D 16 2500 330.0 16.4 6.5 10.3 2.1 8.0 16.0 Q1
INA125UA/2K5 SOIC D 16 2500 330.0 16.4 6.5 10.3 2.1 8.0 16.0 Q1

Pack Materials-Page 1
 PACKAGE MATERIALS INFORMATION

www.ti.com 3-Jun-2022

TAPE AND REEL BOX DIMENSIONS

Width (mm)
H
W

*All dimensions are nominal

Device Package Type Package Drawing Pins SPQ Length (mm) Width (mm) Height (mm)
INA125U/2K5 SOIC D 16 2500 356.0 356.0 35.0
INA125UA/2K5 SOIC D 16 2500 356.0 356.0 35.0

Pack Materials-Page 2
 PACKAGE MATERIALS INFORMATION

www.ti.com 3-Jun-2022

TUBE

T - Tube
height L - Tube length

W - Tube
width

B - Alignment groove width

*All dimensions are nominal

Device Package Name Package Type Pins SPQ L (mm) W (mm) T (µm) B (mm)
INA125P N PDIP 16 25 506 13.97 11230 4.32
INA125PA N PDIP 16 25 506 13.97 11230 4.32
INA125PAG4 N PDIP 16 25 506 13.97 11230 4.32
INA125U D SOIC 16 40 506.6 8 3940 4.32
INA125UA D SOIC 16 40 506.6 8 3940 4.32

Pack Materials-Page 3
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