Patent ID: 7335872

Claim:
A photocurrent amplifier circuit comprising: a differential amplifier circuit configured to have an input unit including amplifier devices which are connected in parallel; device selector switches, each of which is set for an associated one of said amplifier devices and applies an input voltage to said associated amplifier device, the input voltage deactivating said amplifier device; gain resistors, each of which connects an input of an associated one of said amplifier devices with an output of said differential amplifier circuit; light receiving circuits, each of which is set for an associated one of said amplifier devices and generates a voltage signal in accordance with an amount of received light; and input resistors, each of which connects an input of an associated one of said light receiving circuits with an output of each of said amplifier devices, wherein said differential amplifier circuit amplifies a current signal which flows from each of said light receiving circuits via an associated one of said input resistors into an associated one of said gain resistors.