simple stabiliser

elektorjuly/august 1983 72 simple stabiliser This is a very simple but nonethe- less reliable stabiliser circuit which can be used in place of a 78XX series IC regulator. The heart of the circuit is based on a type CA 3130 operational amplifier, Al, and one transistor. The reference voltage, Uref, is derived from the output by means of R1 and zener diode Dl and is therefore very stable. Operation cl 150p 1 CA 3130 T1 R1 R2 is simple: if the output voltage, Uout, shows a tendency to rise, the potential difference at junction R2/R3 will increase. The voltage at the non-inverting input of Al will then become higher than that at the inverting input, because the latter is held at Uref by zener D1. The output of Al therefore increases resulting in T1 being cut off and in a reduction in the output voltage of the stabiliser. If Uout drops below the nomina) value, the above oper- ation is reversed. The advantage of this circuit is the low voltage drop between input and output, which is dep...