A process- and temperature-independent inverter-comparator for pulse width modulation applications

This paper presents a self-tuning inverter-comparator for a pulse width modulator (PWM) for Class D amplifiers. The inherent threshold voltage of the inverter-comparator, V sub(THC), is independent of process- and temperature-variations by means of a self-tuning mechanism. The measured duty cycle error of the PWM at zero-input is typically 0.5%; an error less than or equal to 2% is typically specified in practical realisations. This is achieved without any post-fabrication trimming or calibration. The PWM is realised by a very simple circuit and can be readily fabricated in a low-cost CMOS process. The PWM prototype ICs met all design specifications and the proposed inverter-comparator is suitable for micropower low-voltage applications including hearing instruments.