BURR-BROWN INA126, INA2126 User Manual

®

40kΩ

10kΩ

10kΩ

40kΩ

INA2126

5

7

8

1

3

4

2

9
6

R

G

V

IN

–

V

IN

+

V+

V–

V

O

= (V

IN

– VIN) G

–

+

80k

R

G

G = 5 +

V

O

= (VIN – VIN) G

–

+

80k
R

G

G = 5 +

40kΩ

10kΩ

10kΩ

40kΩ

12

16

14

13

15

11

10

R

G

V

IN

–

V

IN

+

INA126

INA2126

INA126

INA126

INA2126

INA2126

INA2126

Micro

POWER INSTRUMENTATION AMPLIFIER

Single and Dual Versions

FEATURES

● LOW QUIESCENT CURRENT: 175µA/chan.

● WIDE SUPPLY RANGE:

● LOW OFFSET VOLTAGE: 250

● LOW OFFSET DRIFT: 3

● LOW NOISE: 35nV/√Hz

● LOW INPUT BIAS CURRENT: 25nA max

● 8-PIN DIP, SO-8, MSOP-8 SURFACE- MOUNT

DUAL: 16-Pin DIP, SO-16, SSOP-16

APPLICATIONS

● INDUSTRIAL SENSOR AMPLIFIER:

Bridge, RTD, Thermocouple

● PHYSIOLOGICAL AMPLIFIER:

ECG, EEG, EMG

● MULTI-CHANNEL DATA ACQUISITION

● PORTABLE, BATTERY OPERATED SYSTEMS

±1.35V to ±18V

µV max

µV/°C max

DESCRIPTION

The INA126 and INA2126 are precision instrumentation
amplifiers for accurate, low noise differential signal acquisi­tion. Their two-op-amp design provides excellent perfor­mance with very low quiescent current (175µA/chan.). This,
combined with wide operating voltage range of ±1.35V to
±18V, makes them ideal for portable instrumentation and data
acquisition systems.

Gain can be set from 5V/V to 10000V/V with a single
external resistor. Laser trimmed input circuitry provides
low offset voltage (250µV max), low offset voltage drift
(3µV/°C max) and excellent common-mode rejection.

Single version package options include 8-pin plastic DIP,
SO-8 surface mount, and fine-pitch MSOP-8 surface-mount.
Dual version is available in the space-saving SSOP-16 fine­pitch surface mount, SO-16, and 16-pin DIP. All are speci­fied for the –40°C to +85°C industrial temperature range.

V+

+

V

IN

–

V

IN

International Airport Industrial Park • Mailing Address: PO Box 11400, Tucson, AZ 85734 • Street Address: 6730 S. Tucson Blvd., Tucson, AZ 85706 • Tel: [phone] • Twx: 910-952-1111

Internet: http://www.burr-brown.com/ • FAXLine: [phone] (US/Canada Only) • Cable: BBRCORP • Telex: 066-6491 • FAX: [phone] • Immediate Product Info: [phone]

©1996 Burr-Brown Corporation PDS-1365C Printed in U.S.A. September, 1997

3

8

R

G

1

2

7

40kΩ

10kΩ

10kΩ

40kΩ

4

V–

INA126

6

5

= (VIN – VIN) G

V

O

G = 5 +

–+

80k

R

G

SPECIFICATIONS

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

INA126P, U, E INA126PA, UA, EA

INA2126P, U, E INA2126PA, UA, EA
PARAMETER CONDITIONS MIN TYP MAX MIN TYP MAX UNITS
INPUT

Offset Voltage, RTI ±100 ±250 ±150 ±500 µV

vs Temperature ±0.5 ±3 ✻ ±5 µV/°C

vs Power Supply (PSRR) V
Input Impedance 10
Safe Input Voltage R

Common-Mode Voltage Range V
Channel Separation (dual) G = 5, dc 130 dB
Common-Mode Rejection R

INA2126U (dual SO-16) 80 94 dB
INPUT BIAS CURRENT –10 –25 ✻ –50 nA

vs Temperature ±30 ✻ pA/°C
Offset Current ±0.5 ±2 ✻ ±5nA

vs Temperature ±10 ✻ pA/°C
GAIN G = 5 to 10k ✻ V/V

Gain Equation G = 5 + 80kΩ/R
Gain Error V

vs Temperature G = 5 ±2 ±10 ✻✻ppm/°C
Gain Error V

vs Temperature G = 100 ±25 ±100 ✻✻ppm/°C
Nonlinearity G = 100, V

NOISE

Voltage Noise, f = 1kHz 35 ✻ nV/√Hz

f = 100Hz 35 ✻ nV/√Hz
f = 10Hz 45 ✻ nV/√Hz

= 0.1Hz to 10Hz 0.7 ✻ µVp-p

f

Current Noise, f = 1kHz 60 ✻ fA/√Hz

B

= 0.1Hz to 10Hz 2 ✻ pAp-p

f

B

OUTPUT

Voltage, Positive R

Negative R
Short-Circuit Current Short-Circuit to Ground +10/–5 ✻ mA
Capacitive Load Drive 1000 ✻ pF

FREQUENCY RESPONSE

Bandwidth, –3dB G = 5 200 ✻ kHz

Slew Rate V
Settling Time, 0.01% 10V Step, G = 5 30 ✻ µs

Overload Recovery 50% Input Overload 4 ✻ µs

POWER SUPPLY

Voltage Range ±1.35 ±15 ±18 ✻✻✻ V
Current (per channel) I

TEMPERATURE RANGE

Specification Range –40 +85 ✻✻°C
Operation Range –55 +125 ✻✻°C
Storage Range –55 +125 ✻✻°C
Thermal Resistance,

8-Pin DIP 100 ✻ °C/W

θ

JA

SO-8 Surface-Mount 150 ✻ °C/W
MSOP-8 Surface-Mount 200 ✻ °C/W
16-Pin DIP (dual) 80 ✻ °C/W
SO-16 (dual) 100 ✻ °C/W
SSOP-16 (dual) 100 ✻ °C/W

✻ Specification same as INA126P, INA126U, INA126E; INA2126P, INA2126U, INA2126E.

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.

®

INA126, INA2126

= ±1.35V to ±18V 5 15 ✻ 50 µV/V

S

= 0 (V–)–0.5 (V+)+0.5 ✻✻V

S

= 1kΩ (V–)–10 (V+)+10 ✻✻V

R

S

= 0V ±11.25 ±11.5 ✻✻ V

O

= 0, VCM = ±11.25V 83 94 74 90 dB

S

= ±14V, G = 5 ±0.02 ±0.1 ✻ ±0.18 %

O

= ±12V, G = 100 ±0.2 ± 0.5 ✻ ±1%

O

= ±14V ±0.002 ±0.012 ✻✻ %

O

= 25kΩ (V+)–0.9 (V+)–0.75 ✻✻ V

L

= 25kΩ (V–)+0.95 (V–)+0.8 ✻✻ V

L

9

|| 4 ✻ Ω || pF

G

✻ V/V

G = 100 9 ✻ kHz
G = 500 1.8 ✻ kHz

= ±10V, G = 5 0.4 ✻ V/µs

O

10V Step, G = 100 160 ✻ µs
10V Step, G = 500 1500 ✻ µs

= 0 ±175 ±200 ✻✻ µA

O

2

PIN CONFIGURATION (Single)

Top View 8-Pin DIP, SO-8, MSOP-8

1

R

G

–

2

V

IN

+

3

V

IN

4

V–

8

R

G

7

V+

6

V

O

5

Ref

PIN CONFIGURATION (Dual)

Top View 16-Pin DIP, SO-16, SSOP-16

V
V

R
R

Ref

V

Sense

–
INA

+
INA

V–

1
2
3

GA

4

GA

5

A

6

OA

7

A

8

–

16

V

INB
+

15

V

INB

14

R

GB

13

R

GB

12

Ref

B

11

V

OB

10

Sense

B

9

V+

ABSOLUTE MAXIMUM RATINGS

Power Supply Voltage, V+ to V– ........................................................ 36V

Input Signal Voltage
Input Signal Current

(2)

........................................... (V–)–0.7 to (V+)+0.7V

(2)

...................................................................... 10mA

(1)

Output Short Circuit ................................................................. Continuous

Operating Temperature ................................................. –55°C to +125°C

Storage Temperature ..................................................... –55°C to +125°C

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

NOTES: (1) Stresses above these ratings may cause permanent damage.
(2) Input signal voltage is limited by internal diodes connected to power
supplies. See text.

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.

PACKAGE INFORMATION

PRODUCT PACKAGE NUMBER

PACKAGE DRAWING TRANSPORT

Single

INA126PA 8-Pin DIP 006 INA126PA INA126PA Rails
INA126P 8-Pin DIP 006 INA126P INA126P Rails

INA126UA SO-8 182 INA126UA INA126UA Rails or Reel
INA126U SO-8 182 INA126U INA126U Rails or Reel

INA126EA

INA126E

(2)

" " " " INA126EA-2500 "

(2)

MSOP-8 337 A26

MSOP-8 337 A26

" " " " INA126E-2500 "

Dual

INA2126PA 16-Pin DIP 180 INA2126PA INA2126PA Rails
INA2126P 16-Pin DIP 180 INA2126P INA2126P Rails

INA2126UA SO-16 265 INA2126UA INA2126UA Rails
INA2126U SO-16 265 INA2126U INA2126U Rails

INA2126EA

INA2126E

(2)

" " " " INA2126EA-2500 "

(2)

SSOP-16 322 INA2126EA INA2126EA-250 Reel Only

SSOP-16 322 INA2126E INA2126E-250 Reel Only

" " " " INA2126E-2500 "

NOTES: (1) For detailed drawing and dimension table, see end of data sheet, or Appendix C of Burr-Brown IC Data Book. (2) MSOP-8 and SSOP-16 packages are
available only on 250 or 2500 piece reels. (3) Grade designation is marked on reel.

(1)

PACKAGE MARKING ORDERING NUMBER MEDIA

(3)

(3)

INA126EA-250 Reel Only

INA126E-250 Reel Only

®

3

INA126, INA2126

TYPICAL PERFORMANCE CURVES

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

70

G = 1000

60

GAIN vs FREQUENCY

50

G = 100

40
30

Gain (dB)

20

G = 20

G = 5

10

0

–10

100 1k 10k 100k 1M

Frequency (Hz)

POSITIVE POWER SUPPLY REJECTION

vs FREQUENCY

120

G = 1000

100

80

60

40

20

Power Supply Rejection (dB)

G = 5

G = 100

110

COMMON-MODE REJECTION vs FREQUENCY

100

90
80
70

G = 1000

60
50

G = 100

40
30
20

Common-Mode Rejection (dB)

10

0

10 100 1k 10k 100k 1M

Frequency (Hz)

NEGATIVE POWER SUPPLY REJECTION

vs FREQUENCY

120

100

80

G = 1000

60

40

20

Power Supply Rejection (dB)

G = 5

G = 5

G = 100

0

10 100 1k 10k 100k 1M

Frequency (Hz)

INPUT COMMON-MODE RANGE

15

vs OUTPUT VOLTAGE, V

output swing—see text

10

Limited by A

2

5

V

0

–5

Common-Mode Voltage (V)

–10

V

+

V

–15

+

D/2

–
+

D/2

–

CM

Limited by A

–15V

= ±15V

S

+15V

V

O

Ref

output swing—see text

2

–15 –10 0 5 15–5

Output Voltage (V)

®

INA126, INA2126

0

10 100 1k 10k 100k 1M

Frequency (Hz)

INPUT COMMON-MODE VOLTAGE RANGE

5

vs OUTPUT VOLTAGE, V

4
3
2

Limited by A

VS = ±5V

output swing—see text

2

1
0

= ±5V

S

VS = +5V/0V

V

= 2.5V

REF

–1
–2
–3

Input Common-Mode Voltage (V)

–4

Limited by A

output swing—see text

2

–5

10

–5 –4 5–3 –2 –1 0 1 2 3 4

Output Voltage (V)

4

TYPICAL PERFORMANCE CURVES (CONT)

SETTLING TIME vs GAIN

Gain (V/V)

Settling Time (µs)

1000

100

10

1 10 100 1k

0.01%

0.1%

OUTPUT VOLTAGE SWING

vs OUTPUT CURRENT

012345

Output Current (mA)

Output Voltage (V)

Sourcing Current

Sinking Current

V+

(V+)–1

(V+)–2

(V–)+2

(V–)+1

V–

QUIESCENT CURRENT AND SLEW RATE

vs TEMPERATURE

Temperature (°C)

Quiescent Current (µA)

Slew Rate (V/µs)

300

250

200

150

100

50

0

0.6

0.5

0.4

0.3

0.2

0.1

0

–75 –50 –25 0 25 50 75 100 125

+SR

–SR

VS = ±5V

VS = ±1.35V

I

Q

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

100

10

Input Voltage Noise (nV/√Hz)

1

10

–2
–4
–6

Offset Voltage Change (µV)

–8

–10

INPUT-REFERRED NOISE vs FREQUENCY

Voltage Noise

Current Noise

1 10 100 10k1k

Frequency (Hz)

INPUT-REFERRED OFFSET VOLTAGE WARM-UP

8
6
4
2
0

01 1023456789

Time After Turn-On (ms)

1k

100

Input Current Noise (fA/√Hz)

10

(Noise)

TOTAL HARMONIC DISTORTION+NOISE

1

0.1

THD+N (%)

0.01

0.001
10 100 1k

vs FREQUENCY

Frequency (Hz)

G = 5

RL = 10kΩ

RL = 100kΩ

10k

®

5

INA126, INA2126

TYPICAL PERFORMANCE CURVES (CONT)

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

SMALL-SIGNAL RESPONSE, G = 5

20mV/div

5V/div

50µs/div

SMALL-SIGNAL RESPONSE, G = 100

20mV/div

50µs/div

VOLTAGE NOISE, 0.1Hz to 10HzLARGE-SIGNAL RESPONSE, G = 5

0.2µV/div

50µs/div

®

INA126, INA2126

CHANNEL SEPARATION vs FREQUENCY, RTI

160
150
140
130
120
110
100

Separation (dB)

RL = 25kΩ

90
80
70
60

100 1k 10k 100k 1M

Measurement limited
by amplifier or
measurement noise.

(Dual Version)

G = 100

G = 5

Frequency (Hz)

6

500ms/div

G = 1000

APPLICATION INFORMATION

10kΩ

OPA237

±10mV

Adjustment Range

100Ω

100Ω

100µA

1/2 REF200

100µA

1/2 REF200

V+

V–

R

G

INA126

Ref

V

O

✻

V

IN

–

V

IN

+

✻ Dual version has
external sense connection.

Figure 1 shows the basic connections required for operation
of the INA126. 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 ensure 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.

Dual versions (INA2126) have feedback sense connections,

and SenseB. These must be connected to their respec-

Sense

A

tive output terminals for proper operation. The sense con­nection can be used to sense the output voltage directly at the
load for best accuracy.

SETTING THE GAIN

Gain is set by connecting an external resistor, R

, as shown:

G

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 in
gains of approximately 100 or greater.

OFFSET TRIMMING

The INA126 and INA2126 are 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 the Ref terminal is added to the output signal. An
op amp buffer is used to provide low impedance at the Ref
terminal to preserve good common-mode rejection.

G =5+

80kΩ

Commonly used gains and R

R

G

resistor values are shown in

G

(1)

Figure 1.
The 80kΩ term in equation 1 comes from the internal metal film

resistors which are laser trimmed to accurate absolute values.
The accuracy and temperature coefficient of these resistors are
included in the gain accuracy and drift specifications.

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

, also affects gain. RG’s contribution to

G

gain accuracy and drift can be directly inferred from the gain

DESIRED GAIN RGNEAREST 1%

(V/V) (Ω)R

5NCNC
10 16k 15.8k
20 5333 5360
50 1779 1780

100 842 845
200 410 412

500 162 162
1000 80.4 80.6
2000 40.1 40.2
5000 16.0 15.8

10000 8.0 7.87

NC: No Connection.

FIGURE 1. Basic Connections.

Also drawn in simplified form:

VALUE

G

+

V

IN

R

–

V

IN

INA126

G

✻

Ref

FIGURE 2. Optional Trimming of Output Offset Voltage.

V+

Pin numbers are
for single version

3

+

V

IN

8

R

G

1

–

V

IN

2

V

O

✻ Dual version has
external sense connection.

7

0.1µF

7

INA126

A

1

10kΩ

A

2

V–

4

40kΩ

10kΩ

40kΩ

0.1µF

6

✻

5

Ref

INA126, INA2126

G = 5 +

VO = (VIN – VIN) G

Load

80k
R

G

–+

+

V

O

–

®

INPUT BIAS CURRENT RETURN

The input impedance of the INA126/2126 is extremely
high—approximately 10

9

Ω. However, a path must be pro-

vided for the input bias current of both inputs. This input
bias current is typically –10nA (current flows out of the
input terminals). 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
advantages of lower input offset voltage due to bias current
and better high-frequency common-mode rejection.

Microphone,

Hydrophone

etc.

INA126

The internal op amp A2 is identical to A1 and its output
swing is limited to typically 0.7V from the supply rails.
When the input common-mode range is exceeded (A2’s
output is saturated), A1 can still be in linear operation and
respond to changes in the non-inverting input voltage. The
output voltage, however, will be invalid.

LOW VOLTAGE OPERATION

The INA126/2126 can be operated on power supplies as low
as ±1.35V. Performance remains excellent with power sup­plies ranging from ±1.35V 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 ensure that the common­mode voltage remains within its linear range. See “Input
Common-Mode Voltage Range.”

The INA126/2126 can be operated from a single power
supply with careful attention to input common-mode range,
output voltage swing of both op amps and the voltage
applied to the Ref terminal. Figure 4 shows a bridge ampli­fier circuit operated from a single +5V power supply. The
bridge provides an input common-mode voltage near 2.5V,
with a relatively small differential voltage.

47kΩ47kΩ

Thermocouple

10kΩ

Center-tap provides

bias current return.

INA126

INA126

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

INPUT COMMON-MODE RANGE

The input common-mode range of the INA126/2126 is
shown in typical performance curves. The common-mode
range is limited on the negative side by the output voltage
swing of A

, an internal circuit node that cannot be measured

2

on an external pin. The output voltage of A2 can be ex­pressed as:

= 1.25 VIN – (VIN – VIN) (10kΩ/RG) (2)

V

O2

–+–

(Voltages referred to Ref terminal, pin 5)

INPUT PROTECTION

The inputs are protected with internal diodes connected to
the power supply rails. These diodes will clamp the applied
signal to prevent it from exceeding the power supplies by
more than approximately 0.7V. If the signal source voltage
can exceed the power supplies, the source current should be
limited to less than 10mA. This can generally be done with
a series resistor. Some signal sources are inherently current­limited and do not require limiting resistors.

CHANNEL CROSSTALK—DUAL VERSION

The two channels of the INA2126 are completely indepen­dent, including all bias circuitry. At DC and low frequency
there is virtually no signal coupling between channels.
Crosstalk increases with frequency and is dependent on
circuit gain, source impedance and signal characteristics.

As source impedance increases, careful circuit layout will
help achieve lowest channel crosstalk. Most crosstalk is
produced by capacitive coupling of signals from one channel
to the input section of the other channel. To minimize
coupling, separate the input traces as far as practical from
any signals associated with the opposite channel. A grounded
guard trace surrounding the inputs helps reduce stray cou­pling between channels. Carefully balance the stray capaci­tance of each input to ground, and run the differential inputs
of each channel parallel to each other, or directly adjacent on
top and bottom side of a circuit board. Stray coupling then
tends to produce a common-mode signal that is rejected by
the IA’s input.

®

INA126, INA2126

8

+5V

The ADS7817’s V
conversion rate 10kS/s or slower assures enough current to turn on the

input current is proportional to conversion rate. A

REF

reference diode. Converter input range is ±1.2V. Output swing limitation of
INA126 limits the A/D converter to somewhat greater than 11 bits of range.

7

INA126

A

1

10kΩ

A

2

40k

10kΩ

40kΩ

Ω

Bridge
Sensor

2.5V + ∆V

2.5V – ∆V

R

3

8

G

1

2

4

A similar instrumentation amplifier, INA125, provides
an internal reference voltage for sensor excitation
and/or A/D converter reference.

FIGURE 4. Bridge Signal Acquisition—Single 5V Supply.

6

5

✻

1.2V

68

4

R

, C1, R2:

1

340Hz LP

R

1

1kΩ

C

1

0.47µF

R

2

1kΩ

33µA

REF1004C-1.2

8

2

+IN

ADS7817

3

–IN

12-Bit

A/D

1

V

REF

4

✻ Dual version has external
sense connection. Pin numbers
shown are for single version.

INA126 and ADS7817
are available in fine-pitch
MSOP-8 package

6

Serial

Data

5

Chip

Select

7

Clock

C

Ck

D

S

A

1

IB Error

OPA177 ±1.5nA
OPA130 ±20pA
OPA602 ±1pA
OPA129 ±100fA

FIGURE 5. Differential Voltage-to-Current Converter.

–

V

IN

+

R

INA126

G

✻

Ref

R

1

I

B

A

1

V

I

= • G

O

IN

R

1

I

O

Load

✻ Dual version has external sense connection.

®

9

INA126, INA2126