In this paper, the hardware and the software design and also the realization of a PWM transistor inverter control circuit are given. A mathematical analysis for computing the switching angles is performed for both a single-phase and a three-phase inverters. The pre-calculated switching patterns which eliminate low order harmonics of the inverter output are stored in the EPROM. A simple digital control circuit associated with an EPROM is used to generate the control signals for the switching transistors of the inverter. The description of the designed digital control circuit for single - and three-phase inverter are included. Output waveforms for the designed circuit and the PWM inverter circuits are presented.