Patent ID: 8120387

Claim:
A receiving circuit, comprising: a comparing circuit which compares an input signal with a reference voltage and outputs a signal with either a first level when the input signal is larger than the reference voltage or a second level when the input signal is smaller than the reference voltage as a comparison result; a first storage circuit which stores an output level of the comparing circuit for a next one cycle; a second storage circuit which stores an output level of the first storage circuit for a next one cycle; and a voltage controlling circuit which controls a level of the reference voltage in each cycle on the basis of output levels of the first storage circuit and the second storage circuit, wherein the voltage controlling circuit makes a level of the reference voltage highest in case that output levels of the first storage circuit and the second storage circuit are the first level together, and makes a level of the reference voltage second highest in case that an output level of the first storage circuit is the first level and an output level of the second storage circuit is the second level, and makes a level of the reference voltage third highest in case that an output level of the first storage circuit is the second level and an output level of the second storage circuit is the first level, and makes a level of the reference voltage lowest in case that output levels of the first storage circuit and the second storage circuit are the second level together, and wherein the voltage controlling circuit comprises an electronic circuit in which a first resistor and a second resistor, which are connected in series together, are arranged between a power supply and the ground, and in which voltage at a connection point of the first resistor and the second resistor is provided to the comparing circuit as a reference voltage, and in which a third resistor and a first transistor, which is turned on and off by an output level of the first storage circuit, are connected in series together and are arranged between the connection point and the ground, and in which a fourth resistor and a second transistor, which is turned on and off by an output level of the second storage circuit, are connected in series together and are arranged between the connection point and the ground.