Patent ID: 6841771
Filing Date: 2005-01-11
Classification: H01L,H04B

Abstract:
1. An optical coupling device, comprising a primary side circuit including a light emitting element to convert an input electric signal to an optical and signal; and a secondary side circuit including a light-receiving element arranged in a vicinity of the light emitting element so as to face the light emitting element, the light-receiving element accepting the optical signal to convert the optical signal into an electric signal for output, wherein the secondary side circuit includes an impedance variable circuit arranged in a negative feedback path of a current-to-voltage converting amplifier for amplifying the photoelectric current produced from photo-electric conversion by the light-receiving element to generate a voltage, the impedance variable circuit changing an impedance based on a level of the input photoelectric current, the impedance variable circuit lowering a given gain of the converting amplifier with a rising level of input photoelectric current.