Patent ID: 7259631
Filing Date: 2007-08-21
Classification: H03F

Abstract:
1. A photoreceptor amplifier circuit comprising: a differential amplifier circuit, which includes a differential transistor pair constituted of two transistors and active loads corresponding to said differential transistor pair, said differential amplifier circuit outputting a voltage according to an output current of a photoreceptor; and a correcting current generation circuit for generating a correcting current based on a current difference between said two transistors and supplying the correcting current to said differential amplifier circuit, wherein said correcting current generation circuit generates said correcting current by dividing a collector voltage difference between said two transistors by a common collector output resistance of said two transistors, wherein said correcting current generation circuit includes: a first current mirror circuit including a first and second transistors each having a collector output resistance same as the common collector output resistance; a voltage difference generation circuit for generating a voltage difference between two outputs of said first current mirror circuit, said voltage difference being same as the collector voltage difference; and a current difference generation circuit for generating a difference between two output currents of said first current mirror circuit.