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.