This circuit utilizes a triangle wave generator and comparator to generate a 500 kHz pulse-width modulated (PWM) waveform with a duty cycle that is inversely proportional to the input voltage. An op amp and comparator generate a triangle waveform which is applied to the inverting input of a second comparator. The input voltage is applied to the non-inverting input of this second comparator. By comparing the input waveform to the triangle wave, a PWM waveform is produced.