DC Converter 12V to 1.5V at 4A by 78S40
The 78S40 is a very old, but still useful power conversion chip. It contains a 1.25V reference, comparator, gating, output transistor, flyback diode and an uncommitted operational amplifier, which is not used here, and draws very little power. As the internal transistor and diode are good only for 1A maximum, I had to use external parts instead. Even so, the circuit is simple enough! A P-channel MOSFET was used as power switch, and an unknown toroid from my junk box was pressed into service for the filter choke. The circuit works very well, with an efficiency of better than 60%, which is superb for such a low voltage output! [....] Link
