Datasheet INA129UA-2K5, INA129U, INA129PA, INA128UA, INA128U-2K5 Datasheet (Burr Brown)

©1995 Burr-Brown Corporation PDS-1296C Printed in U.S.A. October, 1996

A

1

A

2

A

3

40kΩ40kΩ

40kΩ40kΩ

V

IN

2

1

8

3

6

5

V

IN

R

G

V+

V–

INA128, INA129

Ref

V

O

INA128:

G = 1 +

50kΩ

R

G

INA129:

G = 1 +

49.4kΩ
R

G

–

+

Over-Voltage

Protection

25kΩ

(1)

25kΩ

(1)

Over-Voltage

Protection

4

7

NOTE: (1) INA129: 24.7kΩ

FEATURES

● LOW OFFSET VOLTAGE: 50µV max

● LOW DRIFT: 0.5

µV/°C max

● LOW INPUT BIAS CURRENT: 5nA max

● HIGH CMR: 120dB min

● INPUTS PROTECTED TO

±40V

● WIDE SUPPLY RANGE:

±2.25 to ±18V

● LOW QUIESCENT CURRENT: 700

µA

● 8-PIN PLASTIC DIP, SO-8

DESCRIPTION

The INA128 and INA129 are low power, general
purpose instrumentation amplifiers offering excellent
accuracy. Their versatile 3-op amp design and small
size make them ideal for a wide range of applications.
Current-feedback input circuitry provides wide band­width even at high gain (200kHz at G = 100).

A single external resistor sets any gain from 1 to
10,000. INA128 provides an industry standard gain
equation; INA129’s gain equation is compatible with
the AD620.

The INA128/INA129 is laser trimmed for very low
offset voltage (50µV), drift (0.5µV/°C) and high com­mon-mode rejection (120dB at G ≥ 100). It operates
with power supplies as low as ±2.25V, and quiescent
current is only 700µA—ideal for battery operated
systems. Internal input protection can withstand up to
±40V without damage.

The INA128/INA129 is available in 8-pin plastic
DIP, and SO-8 surface-mount packages, specified for
the –40°C to +85°C temperature range. The INA128
is also available in dual configuration, the INA2128.

Precision, Low Power

INSTRUMENT ATION AMPLIFIERS

®

INA128
INA129

APPLICA TIONS

● BRIDGE AMPLIFIER

● THERMOCOUPLE AMPLIFIER

● RTD SENSOR AMPLIFIER

● MEDICAL INSTRUMENTATION

● DATA ACQUISITION

INA128

INA128

INA129

INA129

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SPECIFICATIONS

At TA = +25°C, VS = ±15V, RL = 10kΩ, unless otherwise noted.

INA128P, U INA128PA, UA
INA129P, U INA129PA, UA

PARAMETER CONDITIONS MIN TYP MAX MIN TYP MAX UNITS

✻ Specification same as INA128P, U or INA129P, U.
NOTE: (1) Input common-mode range varies with output voltage—see typical curves. (2) Guaranteed by wafer test. (3) Temperature coefficient of the 50kΩ (or 49.4kΩ)
term in the gain equation. (4) Nonlinearity measurements in G = 1000 are dominated by noise. Typical nonlinearity is ±0.001%.

INPUT

Offset Voltage, RTI

Initial T

A

= +25°C ±10 ±100/G ±50 ±500/G ±25 ±100/G ±125 ±1000/G µV

vs Temperature T

A

= T

MIN

to T

MAX

±0.2 ± 2/G ±0.5 ± 20/G ±0.2 ± 5/G ±1 ± 20/G µV/°C

vs Power Supply V

S

= ±2.25V to ±18V ±0.2 ±20/G ±1 ±100/G ✻ ±2 ±200/G µV/V

Long-Term Stability ±0.1 ±3/G ✻ µV/mo

Impedance, Differential 10

10

|| 2 ✻ Ω || pF

Common-Mode 10

11

|| 9 ✻ Ω || pF

Common-Mode Voltage Range

(1)

VO = 0V (V+) – 2 (V+) – 1.4 ✻✻ V

(V–)

+ 2 (V–) + 1.7 ✻✻ V
Safe Input Voltage ±40 ✻ V
Common-Mode Rejection V

CM

= ±13V, ∆RS = 1kΩ

G=1 80 86 73 ✻ dB

G=10 100 106 93 ✻ dB

G=100 120 125 110 ✻ dB

G=1000 120 130 110 ✻ dB

BIAS CURRENT ±2 ±5 ✻ ±10 nA

vs Temperature ±30 ✻ pA/°C

Offset Current ±1 ±5 ✻ ±10 nA

vs Temperature ±30 ✻ pA/°C

NOISE VOLTAGE, RTI G = 1000, R

S

= 0Ω
f = 10Hz 10 ✻ nV/√Hz
f = 100Hz 8 ✻ nV/√Hz
f = 1kHz 8 ✻ nV/√Hz
f

B

= 0.1Hz to 10Hz 0.2 ✻ µVp-p

Noise Current

f=10Hz 0.9 ✻ pA/√Hz
f=1kHz 0.3 ✻ pA/√Hz
f

B

= 0.1Hz to 10Hz 30 ✻ pAp-p

GAIN

Gain Equation, INA128 1 + (50kΩ/R

G

) ✻ V/V

INA129

1 + (49.4kΩ/RG)

✻

V/V
Range of Gain 1 10000 ✻✻V/V
Gain Error G=1 ±0.01 ±0.024 ✻ ±0.1 %

G=10 ±0.02 ±0.4 ✻ ±0.5 %

G=100 ±0.05 ±0.5 ✻ ±0.7 %

G=1000 ±0.5 ±1 ✻ ±2%

Gain vs Temperature

(2)

G=1 ±1 ±10 ✻✻ppm/°C

50kΩ (or 49.4kΩ) Resistance

(2, 3)

±25 ±100 ✻✻ppm/°C

Nonlinearity V

O

= ±13.6V, G=1 ±0.0001 ±0.001 ✻ ±0.002 % of FSR

G=10 ±0.0003 ±0.002 ✻ ±0.004 % of FSR

G=100 ±0.0005 ±0.002 ✻ ±0.004 % of FSR

G=1000 ±0.001 (Note 4) ✻✻% of FSR

OUTPUT

Voltage: Positive R

L

= 10kΩ (V+) – 1.4 (V+) – 0.9 ✻✻ V

Negative R

L

= 10kΩ (V–) + 1.4 (V–) + 0.8 ✻✻ V
Load Capacitance Stability 1000 ✻ pF
Short-Circuit Current +6/–15 ✻ mA

FREQUENCY RESPONSE

Bandwidth, –3dB G=1 1.3 ✻ MHz

G=10 700 ✻ kHz

G=100 200 ✻ kHz

G=1000 20 ✻ kHz

Slew Rate V

O

= ±10V, G=10 4 ✻ V/µs

Settling Time, 0.01% G=1 7 ✻ µs

G=10 7 ✻ µs

G=100 9 ✻ µs

G=1000 80 ✻ µs

Overload Recovery 50% Overdrive 4 ✻ µs

POWER SUPPLY

Voltage Range ±2.25 ±15 ±18 ✻✻ ✻V
Current, Total V

IN

= 0V ±700 ±750 ✻✻µA

TEMPERATURE RANGE

Specification –40 85 ✻✻°C
Operating –40 125 ✻✻°C

θ

JA

8-Pin Dip 80 ✻ °C/W
SO-8 SOIC 150 ✻ °C/W

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 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.

ORDERING INFORMATION

PACKAGE
DRAWING TEMPERATURE

PRODUCT PACKAGE NUMBER

(1)

RANGE

INA128PA 8-Pin Plastic DIP 006 –40°C to +85°C
INA128P 8-Pin Plastic DIP 006 –40°C to +85°C
INA128UA SO-8 Surface-Mount 182 –40°C to +85°C
INA128U SO-8 Surface-Mount 182 –40°C to +85°C

INA129PA 8-Pin Plastic DIP 006 –40°C to +85°C
INA129P 8-Pin Plastic DIP 006 –40°C to +85°C
INA129UA SO-8 Surface-Mount 182 –40°C to +85°C
INA129U SO-8 Surface-Mount 182 –40°C to +85°C

NOTE: (1) For detailed drawing and dimension table, please see end of data
sheet, or Appendix C of Burr-Brown IC Data Book.

PIN CONFIGURATION

8-Pin DIP and SO-8

R

G

V

–

IN

V

+

IN

V–

R

G

V+
V

O

Ref

1
2
3
4

8
7
6
5

Top View

Supply Voltage .................................................................................. ±18V

Analog Input Voltage Range .............................................................±40V

Output Short-Circuit (to ground) .............................................. Continuous

Operating Temperature ................................................. –40°C to +125°C

Storage Temperature ..................................................... –40°C to +125°C

Junction Temperature .................................................................... +150°C

Lead Temperature (soldering, 10s)............................................... +300°C

ABSOLUTE MAXIMUM RATINGS

TYPICAL PERFORMANCE CURVES

At TA = +25°C, VS = ±15V, unless otherwise noted.

COMMON-MODE REJECTION vs FREQUENCY

Frequency (Hz)

Common-Mode Rejection (dB)

10 100 10k 1M1k

140

120

100

80

60

40

20

0

100k

G = 1V/V

G = 10V/V

G = 100V/V

G = 1000V/V

POSITIVE POWER SUPPLY REJECTION

vs FREQUENCY

Frequency (Hz)

Power Supply Rejection (dB)

140

120

100

80

60

40

20

0

10 100 1k 10k 100k 1M

G = 100V/V

G = 1000V/V

G = 1V/V

G = 10V/V

INPUT COMMON-MODE RANGE

vs OUTPUT VOLTAGE, V

S

= ±5, ±2.5V

Output Voltage (V)

Common-Mode Voltage (V)

–5

5
4
3
2
1

0
–1
–2
–3
–4
–5

–4 –3 –2 –1 0 1 2 3 4 5

VS = ±5V
V

S

= ±2.5V

G = 1

G = 1

G ≥ 10

G ≥ 10

G ≥ 10

G = 1

NEGATIVE POWER SUPPLY REJECTION

vs FREQUENCY

Frequency (Hz)

Power Supply Rejection (dB)

140

120

100

80

60

40

20

0

10 100 1k 10k 100k 1M

G = 100V/V

G = 1000V/V

G = 1V/V

G = 10V/V

INPUT COMMON-MODE RANGE

vs OUTPUT VOLTAGE, V

S

= ±15V

Output Voltage (V)

Common-Mode Voltage (V)

–15 –10 0 5 15–5

15

10

5

0

–5

–10

–15

10

G = 1 G = 1

G ≥ 10

G ≥ 10

V

D/2

–
+

–
+

V

CM

V

O

V

D/2

Ref

–15V

+15V

+

GAIN vs FREQUENCY

60
50
40
30
20
10

0
–10
–20

Gain (dB)

Frequency (Hz)

1k 10k 100k 1M 10M

G = 100V/V

G = 10V/V

G = 1V/V

G = 1000V/V

INPUT OVER-VOLTAGE V/I CHARACTERISTICS

5
4
3
2
1

0
–1
–2
–3
–4
–5

Input Current (mA)

Input Voltage (V)

–50 –40 –30 –20 –10 10 20 30 40050

G = 1V/V

G = 1V/V

G = 1000V/V

G = 1000V/V

V

IN

I

IN

–15V

+15V

Flat region represents
normal linear operation.

TYPICAL PERFORMANCE CURVES (CONT)

At TA = +25°C, VS = ±15V, unless otherwise noted.

INPUT- REFERRED NOISE vs FREQUENCY

Frequency (Hz)

Input-Referred Voltage Noise (nV/√ Hz)

110 1k100

1k

100

10

1

10k

G = 1V/V

G = 10V/V

100

10

1

0.1

Input Bias Current Noise (pA/√ Hz)

Current Noise

G = 100, 1000V/V

SETTLING TIME vs GAIN

Gain (V/V)

Settling Time (µs)

100

10

1

1 10 100 1000

0.01%

0.1%

INPUT OFFSET VOLTAGE WARM-UP

10

8
6
4
2

0
–2
–4
–6
–8

–10

0

100

200

300

400

500

Time (µs)

Offset Voltage Change (µV)

INPUT BIAS CURRENT vs TEMPERATURE

2

1

0

–1

–2

–75 –50 –25 0 25 50 75 100 125

Temperature (°C)

Input Bias Current (nA)

I

OS

I

B

Typical IB and I

OS

Range ±2nA at 25°C

QUIESCENT CURRENT and SLEW RATE

vs TEMPERATURE

Temperature (°C)

Quiescent Current (µA)

0.85

0.8

0.75

0.7

0.65

0.6

6

5

4

3

2

1

–75 –50 –25 0 25 50 75 100 125

Slew Rate (V/µs)

I

Q

Slew Rate

TYPICAL PERFORMANCE CURVES (CONT)

At TA = +25°C, VS = ±15V, unless otherwise noted.

OUTPUT VOLTAGE SWING

vs OUTPUT CURRENT

(V+)
(V+)–0.4
(V+)–0.8
(V+)–1.2

(V+)+1.2
(V–)+0.8
(V–)+0.4

V–

01234

Output Current (mA)

Output Voltage (V)

OUTPUT VOLTAGE SWING

vs POWER SUPPLY VOLTAGE

V+

(V+)–0.4

(V+)–0.8

(V+)–1.2

(V–)+1.2

(V–)+0.8

(V–)+0.4

V–

0 5 10 15 20

Power Supply Voltage (V)

Output Voltage Swing (V)

+25°C

+85°C

–40°C

+25°C

–40°C

+85°C

RL = 10kΩ

+85°C

–40°C

SHORT-CIRCUIT OUTPUT CURRENT

vs TEMPERATURE

18
16
14
12
10

8
6
4
2
0

–75 –50 –25 0 25 50 75 100 125

Temperature (°C)

Short Circuit Current (mA)

–I

SC

+I

SC

MAXIMUM OUTPUT VOLTAGE vs FREQUENCY

Frequency (Hz)

Peak-to-Peak Output Voltage (Vpp)

30

25

20

15

10

5

0

1k 10k 100k 1M

G = 1

G = 10, 100

G = 1000

TOTAL HARMONIC DISTORTION + NOISE

vs FREQUENCY

Frequency (Hz)

THD + N (%)

100 1k 10k

1

0.1

0.01

0.001
100k

VO = 1Vrms

G = 1

R

L

= 10kΩ

G = 10V/V

R

L

= 100kΩ

G = 100, RL = 100kΩ

G = 1, RL = 100kΩ

500kHz Measurement
Bandwidth

Dashed Portion
is noise limited.

TYPICAL PERFORMANCE CURVES (CONT)

At TA = +25°C, VS = ±15V, unless otherwise noted.

LARGE-SIGNAL

(G = 1, 10)

SMALL-SIGNAL

(G = 100, 1000)

SMALL-SIGNAL

(G = 1, 10)

LARGE-SIGNAL
(G = 100, 1000)

VOLTAGE NOISE 0.1 to 10Hz

INPUT-REFERRED, G ≥ 100

20µs/div

5µs/div

20µs/div

5µs/div

1s/div

0.1µV/div

5V/div

G = 1

G = 10

5V/div

G = 100

G = 1000

20mV/div

G = 1

G = 10

20mV/div

G = 100

G = 1000

A

1

A

2

A

3

6

40kΩ40kΩ

40kΩ40kΩ

7

4

3

8

1

2

V

IN

V

IN

R

G

V+

V–

INA128, INA129

–

+

5

Over-Voltage

Protection

25kΩ

(1)

25kΩ

(1)

Over-Voltage

Protection

Load

V

O

= G • (VIN – VIN)

+

–

0.1µF

0.1µF

+

–

V

O

R

G

Also drawn in simplified form:

INA128

Ref

V

O

V

IN

–

V

IN

+

Ref

NOTE: (1) INA129: 24.7kΩ

APPLICATION INFORMATION

Figure 1 shows the basic connections required for operation
of the INA128/INA129. Applications with noisy or high
impedance power supplies may require decoupling capaci­tors close to the device pins as shown.

The output is referred to the output reference (Ref) terminal
which is normally grounded. This must be a low-impedance
connection to assure good common-mode rejection. A resis­tance of 8Ω in series with the Ref pin will cause a typical
device to degrade to approximately 80dB CMR (G = 1).

SETTING THE GAIN

Gain is set by connecting a single external resistor, R

G

,

connected between pins 1 and 8:

INA129: (2)

Commonly used gains and resistor values are shown in
Figure 1.

The 50kΩ term in Equation 1 (49.4kΩ in Equation 2) comes
from the sum of the two internal feedback resistors of A

1

and

A

2

. These on-chip metal film resistors are laser trimmed to

INA128: (1)

G = 1+

50 kΩ

R

G

FIGURE 1. Basic Connections.

accurate absolute values. The accuracy and temperature
coefficient of these internal resistors are included in the gain
accuracy and drift specifications of the INA128/INA129.

The stability and temperature drift of the external gain
setting resistor, R

G

, also affects gain. RG’s contribution to
gain accuracy and drift can be directly inferred from the gain
equation (1). Low resistor values required for high gain can
make wiring resistance important. Sockets add to the wiring
resistance which will contribute additional gain error (possi­bly an unstable gain error) in gains of approximately 100 or
greater.

DYNAMIC PERFORMANCE

The typical performance curve “Gain vs Frequency” shows
that, despite its low quiescent current, the INA128/INA129
achieves wide bandwidth, even at high gain. This is due to
the current-feedback topology of the input stage circuitry.
Settling time also remains excellent at high gain.

NOISE PERFORMANCE

The INA128/INA129 provides very low noise in most appli­cations. Low frequency noise is approximately 0.2µVp-p
measured from 0.1 to 10Hz (G ≥ 100). This provides
dramatically improved noise when compared to state-of-the­art chopper-stabilized amplifiers.

G =1+

49. 4 kΩ

R

G

DESIRED RGNEAREST RGNEAREST
GAIN (V/V) (

Ω) 1% R

G

(Ω)(Ω) 1% RG (Ω)

1NCNCNCNC
2 50.00k 49.9k 49.4k 49.9k

5 12.50k 12.4k 12.35k 12.4k
10 5.556k 5.62k 5489 5.49k
20 2.632k 2.61k 2600 2.61k
50 1.02k 1.02k 1008 1k

100 505.1 511 499 499
200 251.3 249 248 249

500 100.2 100 99 100
1000 50.05 49.9 49.5 49.9
2000 25.01 24.9 24.7 24.9
5000 10.00 10 9.88 9.76

10000 5.001 4.99 4.94 4.87

NC: No Connection.

INA128 INA129

50kΩ

R

G

INA128:

G = 1 +

INA129:

G = 1 +

49.4kΩ
R

G

OFFSET TRIMMING

The INA128/INA129 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
trimming the output offset voltage. The voltage applied to
Ref terminal is summed with the output. The op amp buffer
provides low impedance at the Ref terminal to preserve good
common-mode rejection.

INPUT BIAS CURRENT RETURN PATH

The input impedance of the INA128/INA129 is extremely
high—approximately 10

10

Ω. However, a path must be pro-

vided for the input bias current of both inputs. This input
bias current is approximately ±2nA. High input impedance
means that this input bias current changes very little with
varying input voltage.

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 common­mode 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 thermo­couple example in Figure 3). With higher source impedance,
using two equal resistors provides a balanced input with
possible advantages of lower input offset voltage due to bias
current and better high-frequency common-mode rejection.

INPUT COMMON-MODE RANGE

The linear input voltage range of the input circuitry of the
INA128/INA129 is from approximately 1.4V below the
positive supply voltage to 1.7V above the negative supply.
As a differential input voltage causes the output voltage
increase, however, the linear input range will be limited by
the output voltage swing of amplifiers A

1

and A2. So the

FIGURE 2. Optional Trimming of Output Offset Voltage.

10kΩ

OPA177

±10mV

Adjustment Range

100Ω

100Ω

100µA

1/2 REF200

100µA

1/2 REF200

V+

V–

R

G

INA128

Ref

V

O

V

IN

–

V

IN

+

FIGURE 3. Providing an Input Common-Mode Current Path.

47kΩ47kΩ

10kΩ

Microphone,
Hydrophone

etc.

Thermocouple

Center-tap provides

bias current return.

INA128

INA128

INA128

linear common-mode input range is related to the output
voltage of the complete amplifier. This behavior also de­pends on supply voltage—see performance curves “Input
Common-Mode Range vs Output Voltage”.

Input-overload can produce an output voltage that appears
normal. For example, if an input overload condition drives
both input amplifiers to their positive output swing limit, the
difference voltage measured by the output amplifier will be
near zero. The output of A

3

will be near 0V even though both

inputs are overloaded.

LOW VOLTAGE OPERATION

The INA128/INA129 can be operated on power supplies as
low as ±2.25V. Performance remains excellent with power
supplies ranging from ±2.25V to ±18V. Most parameters
vary only slightly throughout this supply voltage range—see
typical performance curves. Operation at very low supply
voltage requires careful attention to assure that the input
voltages remain within their linear range. Voltage swing
requirements of internal nodes limit the input common­mode range with low power supply voltage. Typical perfor­mance curves, “Input Common-Mode Range vs Output
Voltage” show the range of linear operation for ±15V, ±5V,
and ±2.5V supplies.

INA128

R

G

V

O

C

1

0.1µF

OPA130

Ref

R

1

1MΩ

f

–3dB

=

1

2πR

1C1

= 1.59Hz

V

IN

+

–

FIGURE 4. ECG Amplifier With Right-Leg Drive.

FIGURE 8. Differential Voltage to Current Converter.

A

1

IB Error

OPA177 ±1.5nA
OPA131 ±50pA
OPA602 ±1pA
OPA128 ±75fA

SEEBECK
ISA COEFFICIENT
TYPE MATERIAL (

µV/°C) R

1

, R

2

E + Chromel 58.5 66.5kΩ

– Constantan

J + Iron 50.2 76.8kΩ

– Constantan

K + Chromel 39.4 97.6kΩ

– Alumel

T + Copper 38.0 102kΩ

– Constantan

FIGURE 7. Thermocouple Amplifier With RTD Cold-

Junction Compensation.

FIGURE 5. Bridge Amplifier.

FIGURE 6. AC-Coupled Instrumentation Amplifier.

REF102

R

2

R

1

R

3

Pt100

Cu

Cu

V+

K

6

10.0V

4

2

INA128

V

O

Ref

100Ω = Pt100 at 0°C

R

G

INA128

R

G

I

B

R

1

V

IN

–

+

A

1

I

O

Load

I

O

= • G

V

IN

R

1

Ref

INA128

R

G

/2

R

G

= 5.6kΩ

V

O

LA

RL

RA

10kΩ

Ref

NOTE: Due to the INA128’s current-feedback
topology, V

G

is approximately 0.7V less than
the common-mode input voltage. This DC offset
in this guard potential is satisfactory for many
guarding applications.

G = 10

2.8kΩ

V

G

V

G

2.8kΩ

1/2

OPA2131

390kΩ

390kΩ

1/2

OPA2131

300Ω

+5V

2.5V – ∆V

2.5V + ∆V

R

G

INA128

V

O

Ref