Semiconductor integrated circuit which generates waveforms which are out of phase with each other

Abstract

A semiconductor integrated circuit comprises a phase control unit for shifting the phase of an input signal by two or more different fixed phases so as to generate two or more output signals out of phase. A phase detector detects phase differences among the two or more output signals from the phase control unit, and generates one or more correction signals each having a value corresponding to a deviation of one of the detected phase differences from a desired phase difference. The phase detector feeds the one or more correction signals back to the phase control unit so as to make the detected phase differences equal to desired phase differences, respectively. Preferably, the phase control unit can include first and second phase shifters each for shifting the phase of the input signal by a fixed phase, a variable capacitor for capacity adjustment connected in parallel to the first phase shifter and having a control terminal, a first amplifier connected to the first phase shifter, and a second amplifier connected to the second phase shifter. In this case, amplifiers included in the phase control unit are only the first and second amplifiers which are front-end amplifiers. Accordingly, the chip area can be reduced, and the amount of current flowing in the semiconductor integrated circuit can be reduced.