A process-independent threshold voltage inverter-comparator for pulse width modulation applications

This paper presents a novel self-tuning inverter-comparator for a pulse width modulator. The inherent threshold voltage of the inverter-comparator is made independent of temperature and process 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 /spl les/2% is typically specified. This is achieved without any post-fabrication trimming. The PWM is realized by a very simple circuit and can be readily fabricated in a low-cost digital CMOS process. The prototype IC met all design specifications and is suitable for micropower low-voltage applications including hearing instruments.