Abstract: A digital current regulator circuit, especially useful for a DC motor, is described which is fed directly, i.e., without power transformers, from the AC mains, via power transistors (T1-T4) that are controlled by pulse modulation and which can work in four-quadrant operation. An A/D converter (12) generates from samples of the motor current, an actual-value signal in the form of a multi-bit parallel binary code; and a binary comparator (20) compares the actual-value code with a theoretical-value code and generates binary error signals if the actual value is greater or less than the theoretical value. To provide DC-isolation of the power transistors and associated circuitry from the control circuitry that generates the error signals, the parallel bits of the actual-value code are transmitted to the control circuitry through an opto-electronic coupler (14). Other opto-electronic couplers (16, 30) can be provided to transmit other control signals.