Gate supply for regulating transistor derived from vehicle battery - comprising voltage multiplier and limiter to provide constant potential source

The regulating transistor is a MOS type power device. To provide the required constant and sufficiently high gate voltage a voltage multiplier is connected between the widely varying main power supply (U1) for the vehicle and the transistor gate. Typically the voltage multiplier circuit comprises an oscillator driving a switching transistor (11). The resulting chopped output is applied to a conventional diode and capacitor multiplier which terminates in a smoothing capacitor (21). The multiplier can be with advantage made as an integrated circuit of the n-channel MOS type, and thus be part of the regulating transistor chip. The oscillator may be one used in common with other circuits on the vehicle. The output voltage (U2) of the multiplier is normally regulated, for example by a Zener diode.