The purpose of controlling the speed of dc motors can be accomplished by various methods. Phase-locked loop control is one of the most convenient and efficient methods for the same. The Phase-locked loop principle has been used in applications such as FM (frequency modulation), stereo decoders, frequency synthesized transmitters and receivers, FM demodulators and frequency shift keying (FSK) decoders. This paper explains the phase-locked loop based speed control of a dc motor.