12V

1k

10k

10k

1k

1M

5V

100k

R210M

R110M

IC1AMAX4477 IC1B

MAX4477

C14.7 pF

0.1 �F1000 pF

100 pF0.1 �F

0.1 �F

0.1 �F

0.01 �F

PINDIODE

–

+–

+

GAMMARADIATION

5V

IC2AMAX4477

100 pF

0.1 �F0.01 �F–

+

5V

28

36

52

1

4

4

1

18

3

IC3MAX987

0.1 �F

–

+

5V

4

5

2

3

7

1k

10k

150k

10k

IC2BMAX4477

0.01 �F

100 pF

–

+

6

57

VOUT

TEST POINT 1

F igure 1

When a single gamma photon with sufficient energy strikes the PIN photodiode in this circuit, the output of the com-parator pulses high.