Photelectric amplifier having plural actuable feedback paths

Details Photelectric amplifier having plural actuable feedback paths Photelectric amplifier having plural actuable feedback paths

1987-06-24

1988-12-06

Nelms, David C.

Radiant energy

Photocells; circuits and apparatus

Photocell controlled circuit

330 59, H01J 4014

Patent

active

047897775

ABSTRACT:
A photoelectric amplifier in a camera exposure system, in which a photodiode is connected across the inputs of an operational amplifier and charges an integrating circuit in a feedback path across the operational amplifier. The resistance of the feedback path can be varied in response to the film sensitivity. The output of the operational amplifier is compared against a films speed reference voltage. Thereby, a reduced range of film speed reference voltages need to be provided because of the optional gain of the photovoltage.

REFERENCES:
patent: 4216434 (1980-08-01), Wermuth
patent: 4426624 (1984-01-01), Beauducel et al.
patent: 4439739 (1984-03-01), Kilian et al.
patent: 4459475 (1984-07-01), Flint et al.
patent: 4508686 (1985-01-01), Shaber et al.
patent: 4626677 (1986-12-01), Browne
patent: 4673807 (1987-06-01), Kobayashi et al.

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