Figure 29. High input Z, DC differential amplifier

1/4

LM2902

R1

100 kΩ

R2

100 kΩ

R4

100 kΩ

R3

100 kΩ

+V 2

+V 1

Vo

1/4

LM2902

eo = [ 1 +

] (e2 - e1)

As shown eo = (e2 - e1)

R4

R3

Figure 30. Low drift peak detector

I B

2N 92 9

0.00 1 µF

I B

3R

3 MΩ

I B

Input current

compensation

eo

I B

e I

1/4

LM2902

Zo

Z I

C

1 µF

2I B

R

1 MΩ

2I B

*

1/4

LM2902

1/4

LM2902

* Polycarbonate or polyethylene

Figure 31. Using symmetrical amplifiers to reduce input current (general concept)

1/4

LM2902

I B

2N 929

0.001µF

I B

3 MΩ

I B

e o

I I

e I

I B

I B

Aux. amplifier for input

current compensation

1.5 MΩ

1/4

LM2902

LM2902W

Typical single-supply applications

DS3575 - Rev 11

page 12/20