This paper presents a new concept for a pulse width modulator based on a voltage-variable phase shifter. A square waveform and a phase shifted version of itself is fed to a logic AND gate, which generates an output signal with 0 to 50% duty cycle. By using a network of inverters after the AND gate, the duty cycle can reach up to 100%. The phase shifter circuit is implemented using a novel phase-locked loop approach and it has a range of -180/spl deg/ to +180/spl deg/.