Low Dissipation Regulator

30V 1>5pA D1 le 3mm red Cl Tant. T 2p 16 O *see text ELEKTOR ELECTRONICS JULY 1989 SUPPLEMENT LOW DISSIPATION REGULATOR With the advent of the now well-known three-pin voltage reg- ulators, power supplies are taken for granted. Yet, there are cases where such a regulator is not wholly satisfactory. This type of reg- ulator needs a fairly large potential drop across it (typically not less than 3 V) and draws a relatively high quiescent current (typi- cally 6 mA for a 78xx). The regulator presented here is particularly attractive for battery-operated equipments and offers: • variable, very stable output voltage; • low potential drop (some tenths of a volt); • very small quiescent current (20-30 pA). In principle, the regulator is a normal series type. The voltage reference is obtained from a common or garden red LED that must draw not less, nor much more, than 5 [LA. Even at that low cur- rent, an LED has a fairly stable voltage drop. To improve that sta- bility, the current i...