D-class signal amplification circuit

Abstract

A D-class signal amplification circuit of the invention intends to repress the influence by a fluctuations of the power supply voltage with a simplified circuit construction and inexpensive components. The D-class signal amplification circuit includes: a multiplier that multiplies an input signal by a correction coefficient, a first modulator that executes a delta-sigma modulation to an output signal from the multiplier, a D-class amplifier supplied with a power supply voltage VDD, which amplifies an output signal from the first modulator, a voltage conversion circuit that generates a power supply voltage VDD/2 from the power supply voltage VDD, a first low pass filter that inputs a signal converted into a level of VDD/2 on the basis of the output signal outputted from the D-class amplifier, a reference signal generation circuit supplied with VDD/2, which generates a reference signal on the basis of the input signal, a second low pass filter that inputs the reference signal, a first comparator that compares levels of the signals outputted from the first with the second low pass filters, and a coefficient control circuit that increases or decreases the correction coefficient by a predetermined modifying breadth, on the basis of the comparison result.