Patent ID: 8227739

Claim:
A photodetector amplifier circuit that converts a photodetector signal photoelectrically into a photocurrent and controls an on state or an off state of an output transistor according to the photocurrent, the photodetector amplifier circuit comprising: a first control circuit that is connected to a control terminal of the output transistor and controls the on state or the off state of the output transistor according to the photocurrent; and a switch that is connected between the control terminal of the output transistor and a ground voltage terminal and if the output transistor is turned off, discharges the control terminal of the output transistor by making the control terminal of the output transistor conductive with the ground voltage terminal, a first resistance device connected between a second control circuit and a control terminal of a second transistor, wherein the first control circuit comprises the second control circuit and a third control circuit, and the switch is made up of the second transistor.