Abstract: A class D amplifier and a method of pulse width modulation are provided. The class D amplifier includes a sigma delta modulator, a reference signal generator, a pulse width modulator and an amplifier. The sigma delta modulator converts an M bit input signal into N bit pulse code modulation data (M and N are integers and M>N). The reference signal generator counts a system clock and generates an N bit reference signal having 2N data blocks in a sampling period of the pulse code modulation data. The pulse width modulator generates a plurality of pulse width modulation signals having at least two switching periods within the sampling period of the pulse code modulation data. The pulse width modulation signals have pulse widths varied based on a unit time interval of the reference signal. The unit time interval corresponds to one of the data blocks of the reference signal.

Abstract: Disclosed is a digital PWM input D class amplifier by PWM negative feedback. The amplifier includes: digital modulation part for modulating PCM signal of input audio to PWM signal; pulse width generating and correcting part for comparing difference between the PWM signal and output signal negatively fed back, with PWM ramp signal to generate PWM switching signal; output part for generating an amplified output audio signal in response to the PWM switching signal of the pulse width generating and correcting part; and voltage negative feedback loop for negatively feeding back signal of the output part and decreasing a harmonic component to provide the signal to the pulse width generating and correcting part. Thus, the invention compares the negative feedback signal with positive/negative (+/?) saw tooth PWM ramp signal to control On/Off time period of switching transistor and the PWM pulse width and thereby enhance the linearity of the output PWM.