7

LT1024

1024fa

The LT1024 may be inserted directly into OP-10, OP-207

or 0P227 sockets with or without removal of external

nulling components.

The LT1024 is specified over a wide range of power supply

voltages from ±2V to ±18V. Operation with lower supplies

is possible down to ±1.2V (two NiCad batteries).

Advantages of Matched Dual Op Amps

In many applications, the performance of a system

depends on the matching between two operational

amplifiers rather than the individual characteristics of the

two op amps. Two or three op amp instrumentation

amplifiers, tracking voltage references, and low drift active

filters are some of the circuits requiring matching between

two op amps.

The well-known triple op amp configuration illustrates

these concepts. Output offset is a function of the dif-

ference between the offsets of the two halves of the

LT1024. This error cancellation principle holds for a

considerable number of input-referred parameters in

addition to offset voltage and its drift with temperature.

Input bias current will be the average of the two

instrumentation amplifier. Common mode and power

supply rejections will be dependent only on the match

between the two amplifiers (assuming perfect resistor

matching).

The concepts of common mode and power supply rejec-

tion ratio match (∆CMRR and ∆PSRR) are best demon-

strated with a numerical example:

then ∆CMRR = 0.5µV/V or 126dB

then ∆CMRR = 1.5µV/V or 116.5dB.

Typical performance of the instrumentation amplifier:

Input offset voltage = 25µV.

Input bias current = 30pA.

Input offset current = 30pA.

Clearly, the LT1024, by specifying and guaranteeing all of

these matching parameters, can significantly improve the

performance of matching dependent circuits.

Three Op Amp Instrumentation Amplifier

LT1024 • AI01

TRIM R8 FOR GAIN

TRIM R9 FOR DC COMMON MODE REJECTION

TRIM R10 FOR AC COMMON MODE REJECTION

3

2

3

4

11

10

5

6

7

4

6

7

12

OUTPUT

13

14

R4

100Ω

1%

R6

10k

1%

R5

100Ω

1%

R1

10k

1%

R3

2.1k

1%

R7

9.76k

1%

R2

10k

1%

R10

100k

R9

500Ω

R8

200Ω

C1

100pF

LT1037

A

1/2 LT1024

B

1/2 LT1024

–INPUT

+INPUT

15V

15V

–15V

–15V

15V

–15V

GAIN = 1000

–

+

–

+

–

+

APPLICATIO S I FOR ATIO