Just recently I needed to reduce 50V to 24V (and in another application 12V), normally I would just use a 78xx three-terminal regulator and be done with it, but these aren't happy with primary voltages much above 35V.
What I came up with was this simple circuit:
I'm using a TIP 111 - good for a couple of Amp, and with a HFE = 50 - but really any NPN of suitable power handling capability can be used. The zener diode can be any ½W type with voltage around 1V more than you need, e.g. the one in the picture is 12V yielding 10.8V on the output. The resistor is a 2W type.
The PCB layout, on the left, is simply cut with a Dremel tool on single sided piece of PCB material according to the drawing on the left.
Not a circuit as such, but still - I needed a means of making measurements on small SMD (Small Mysterious Devices), so I deviced a measumement pincet for them:
I order to interface my SignalinkUSB to the Yaesu FT-847 Data port you need two components in order to bias the tip for PTT as well as AF, these won't go easily in the 3.5mm plug, so I put them in a "lump" in the cable instead:
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Last modified 25.06.2011, Peter Frenning