REV. A

Information furnished by Analog Devices is believed to be accurate and

reliable. However, no responsibility is assumed by Analog Devices for its

use, nor for any infringements of patents or other rights of third parties that

may result from its use. No license is granted by implication or otherwise

under any patent or patent rights of Analog Devices.

a

OP227

One Technology Way, P.O. Box 9106, Norwood, MA 02062-9106, U.S.A.

Tel: 781/329-4700

www.analog.com

Fax: 781/326-8703

© Analog Devices, Inc., 2002

Dual, Low Noise, Low Offset

Instrumentation Operational Amplifier

PIN CONNECTIONS

NOTE

DEVICE MAY BE OPERATED EVEN IF INSERTION

IS REVERSED; THIS IS DUE TO INHERENT SYMMETRY

OF PIN LOCATIONS OF AMPLIFIERS A AND B

V–(A) AND V–(B) ARE INTERNALLY CONNECTED VIA

SUBSTRATE RESISTANCE

1.

2.

NULL (A)

NULL (A)

–IN (A)

+IN (A)

V– (B)

OUT (B)

V+ (B)

1

V+ (A)

OUT (A)

V– (A)

+IN (B)

–IN (B)

NULL (B)

NULL (B)

A

B

2

3

4

5

6

7

14

13

12

11

10

9

8

FEATURES

Excellent Individual Amplifier Parameters

V Max

Offset Voltage Match, 80

V Max

Offset Voltage Match vs. Temperature, 1

V/ C Max

Low Voltage Noise, 3.9 nV/

÷Hz Max

Fast, 2.8 V/ s Typ

High Gain, 1.8 Million Typ

High Channel Separation, 154 dB Typ

GENERAL DESCRIPTION

The OP227 is the first dual amplifier to offer a combination of

low offset, low noise, high speed, and guaranteed amplifier matching

25

of only 2.7 Hz is an excellent choice for precision low noise designs.

These dc characteristics, coupled with a slew rate of 2.8 V/

ms

typical and a small-signal bandwidth of 8 MHz typical, allow the

designer to achieve ac performance previously unattainable with

op amp based instrumentation designs.

When used in a three op amp instrumentation configuration, the

OP227 can achieve a CMRR in excess of 100 dB at 10 kHz. In

addition, this device has an open-loop gain of 1.5 M typical with

a 1 k

SIMPLIFIED SCHEMATIC

NON

INVERTING

INPUT (+)

INVERTING

INPUT (–)

Q3

Q6

Q1A Q1B

Q2B

Q2A

R3

NULL

R4

Q21

Q11

Q12

Q27

C2

Q23

Q24

R23

R24

Q28

R5

C3

R11 C4

R12

R9

Q22

C1

Q20 Q19

Q26

Q45

Q46

OUTPUT

V-

V+

between amplifiers. These outstanding input current specifications

are realized through the use of a unique input current cancellation

±20 nA and 15 nA

respectively over the full military temperature range.

Other sources of input referred errors, such as PSRR and CMRR,

are reduced by factors in excess of 120 dB for the individual

amplifiers. DC stability is assured by a long-term drift application

of 1.0

mV/month.

Matching between channels is provided on all critical param-

eters including offset voltage, tracking of offset voltage versus

temperature, noninverting bias current, CMRR, and power

supply rejection ratio. This unique dual amplifier allows the

elimination of external components for offset nulling and

frequency compensation.