RECTIFYING CIRCUIT FOR TELEPHONE SET

PURPOSE:To assure the operation of an internal circuit by providing a MOS transistor (TR) with a low forward voltage connecting its gate and source to use its drain and source as a diode as a rectifying element for a full wave rectifying circuit so as to compensate the line voltage drop through the reduction in the voltage drop of the rectifier even if the line voltage drops up to the vicinity of the operation enable voltage of the internal circuit. CONSTITUTION:A DC loop is closed by giving a loop current having a prescribed polarity by a REC 1 to a TKC 3 in response to a hook switch HS turned on, an exchange responds to in response to the operation of a DK 6 to apply exchange connection. TRs Q1-Q4 of VMOS type used for the REC 1 are connected in parallel with a 601 type telephone set or the like, and even if a line voltage drops depending on the relation of the resistance of the telephone line in case of simultaneous off-hook, the voltage drop of the RE 1 is reduced by nearly 0.2V and the applied voltage of the internal circuit is increased by the decrement. Thus, even in using a semiconductor element and an integrated circuit for the internal circuit, then the internal circuit is operated sufficiently and the operating state of a transmission amplifier and a reception amplifier in the TKC 3 is maintained especially to assure the talking.