Patent ID: 6392450
Filing Date: 2002-05-21
Classification: H03K

Abstract:
A comparing circuit comprising:a reference voltage generating part having voltage generating means to which an AC signal whose DC potential fluctuates is supplied and which detects a DC offset potential on the basis of said AC signal and generates a reference potential and first control means for shutting off a power current flowing in said voltage generating means and controlling said voltage generating means to a power down state; and a voltage comparing part having comparing means to which said AC signal and said reference potential are supplied and which compares a voltage level of said AC signal with a voltage level of said reference potential and generates an output signal at a logic level according to a result of said comparison and second control means for shutting off a power current flowing in said comparing means and controlling said comparing means to the power down state, wherein in a receiving mode, said reference voltage generating part and said voltage comparing part are made operative, in a transmitting mode, said reference voltage generating part is made operative and said voltage comparing part is set to the power down state by said second control means, and in a pause mode, said reference voltage generating part and said voltage comparing part are set to the power down state by said first and second control means.