INTEGRATED CIRCUIT POWER SUPPLY

A power supply circuit for supplying current to a MOS depletion load transistor logic circuit for use in programmers for washing machines or controllers for tumble driers. The power supply circuit comprises a depletion MOS transistor having its drain-source path connected between first and second power supply rails. The conductivity of the depletion transistor is controlled by a long tail pair amplifier which compares a reference voltage derived from a source with a voltage derived from the second supply rail using a voltage divider. The voltage divider is constructed to compensate for the effects of process variations on parameters such as threshold voltage and thereby hold the voltage divider ratio substantially constant. The voltage divider comprises two enhancement MOS transistors connected in series between the second supply rail and ground and a current source in the form of a depletion MOS transistor and an enhancement transistor connected in series between the first and second supply rails. The gates of all the transistors are connected to a junction of the current source transistor and the drain of the transistor connected thereto. The voltage across the drain-source of this latter transistor varies with threshold voltage and is added to the voltage on the second rail. Further the voltage at the gates of the enhancement transistors of the voltage divider is used to vary their conductivity.