13

LT1078/LT1079

Micropower, 10ppm/

°C, ±5V Reference

Gain of 10 Difference Amplifier

–

+

+

–

2M

220k

120k 3

2

1

8

4

1/2 LT1078

9V

1M

6

5

7

LT1034BC-1.2

510k

1M

–9V

510k

1%

20k

160k

1%

1/2 LT1078

SUPPLY CURRENT = 9V BATTERY = 115

µA

–9V BATTERY = 85

µA

OUTPUT NOISE = 36

THE LT1078 CONTRIBUTES LESS THAN 3% OF THE TOTAL OUTPUT NOISE AND

DRIFT WITH TIME AND TEMPERATURE. THE ACCURACY OF THE –5V OUTPUT

DEPENDS ON THE MATCHING OF THE TWO 1M RESISTORS

LT1078/79 • TA03

+

–

1M

1M

10M

OUTPUT

0.0035V TO 2.4V

1/2 LT1078

BANDWIDTH= 20kHz

OUTPUT OFFSET= 0.7mV

OUTPUT NOISE= 80

260

BANDWIDTH

THE USEFULNESS OF DIFFERENCE AMPLIFIERS IS LIMITED BY

THE FACT THAT THE INPUT RESISTANCE IS EQUAL TO THE SOURCE

RESISTANCE. THE PICOAMPERE OFFSET CURRENT AND LOW

CURRENT NOISE OF THE LT1078 ALLOWS THE USE OF 1M SOURCE

RESISTORS WITHOUT DEGRADATION IN PERFORMANCE. IN ADDITION,

WITH MEGOHM RESISTORS MICROPOWER OPERATION CAN BE MAINTAINED

LT1078/79 • TA04

–IN

+IN

10M

3V

Picoampere Input Current, Triple Op Amp Instrumentation Amplifier with Bias Current Cancellation

+

–

9

10

8

1/4 LT1079

–

+

+

–

–

+

R2

1M

R2

1M

1/4 LT1079

1/4 LT1079

1/4 LT1079

3

2

1

R1

1M

R1

1M

200k

6

5

7

12

13

14

R3

9.1M

R3

9.1M

9V

4

11

2R

20M

OUTPUT

4mV TO 8.2V

R

10M

2R

20M

–IN

+IN

GAIN = 1 +

()

2R1

R3

R2

= 100 FOR VALUES SHOWN

LT`1078/79 • TA05

INPUT BIAS CURRENT TYPICALLY < 150pA

INPUT RESISTANCE = 3R = 30M FOR VALUES SHOWN

GAIN BANDWIDTH PRODUCT = 1.8MHz