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US 4,096,382 AGranted
Photo-current log-compression circuit
AssigneeFuji Photo Optical Co., Ltd.
InventorsSaburo Numata, Shinichiro Okazaki
Life of this patent
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Abstract
A photoelectric current log-compression circuit includes a log-conversion diode, a photodiode and an operational amplifier for log-compression. In the negative feedback circuit of the operational amplifier is inserted a thermistor to control the amplification degree of the operational amplifier according to the current flowing through the log-conversion diode. Further, a forward voltage of a temperature compensating diode biased with a constant current is applied to the reference voltage of the operational amplifier.
Claims3
A photoelectric current log-compression circuit comprising:
- a reference voltage source and a constant current source, an operational amplifier, a log-conversion diode connected to a non-inversion input terminal of said operational amplifier, a photodetector connected between the non-inversion input terminal and an inversion input terminal of the operational amplifier, a temperature compensating element which changes the resistance thereof inserted in a negative feedback circuit of the operational amplifier to control the amplification degree, and a temperature compensating diode connected between said sources and biased with a predetermined current therefrom, said log-conversion diode being connected between the operational amplifier and a connecting point between said constant current source and said temperature compensating diode whereby a forward voltage of the temperature compensating diode is applied to the operational amplifier.
Dependencies are inferred from the claim text.