A process- and temperature-independent inverter-comparator for pulse widthmodulation applications

This paper presents a self-tuning inverter-comparator for a pulse width mod ulator (PWM) for Class D amplifiers. The inherent threshold voltage of the inverter-comparator, V, is independent of process- and temperature-variatio ns by means of a self-tuning mechanism. The measured duty cycle error of th e PWM at zero-input is typically 0.5%; an error less than or equal to2% is typically specified in practical realisations. This is achieved without any post-fabrication trimming or calibration. The PWM is realised by a very si mple circuit and can be readily fabricated in a low-cost CMOS process. The PWM prototype ICs met all design specifications and the proposed inverter-c omparator is suitable for micropower low-voltage applications including hea ring instruments.