Abstract: A constant current source is provided by a circuit of two metal oxide semiconductor field effect transistors (MOSFET) of the enhancement type having opposite conductivities. One transistor constitutes an input transistor. The other transistor is the output transistor. The drain terminals are connected to the respective polarities of an operating voltage source. The gate terminal of the input transistor is connected to a control voltage source. The source terminals are interconnected and grounded through a resistor. The constant current is available at the drain electrode of the output transistor. If it is desired to produce constant output currents of alternating directions, two such circuits may be interconnected in mirror symmetrical fashion.