Information signal reproducing system having amplifier with selectively decreased gain

摘要

An information signal reproducing circuit for use in an optical information recording/reproducing apparatus, includes a photo detector, a plurality of amplifiers and a plurality of couplings for connecting the amplifiers to each other in a serial manner. A gain of a signal produced by the photo detector is decreased only for a time period during which information is recorded or erased in the information recording/reproducing apparatus. Therefore, in case the amplifiers are serially connected to each other by means of AC couplings, information signal can be correctly read out without being influenced by transients of capacitors constituted of the AC couplings. In case the amplifiers are serially connected to each other by means of DC couplings, information signal can be correctly read out without causing a latch up.