[NLRS] Variable bench supply

[Dr. Gerald N. Johnson, electrical engineer]

The LM-337 does a few amps by itself and is adjustable from 1.2 volts up
to a couple volts below 35 volts, its maximum input voltage. Just
connect the usual stabilizing capacitors from input and output to
ground, connect a 120 ohm resistor from output to common or control on
the chip (the chip works without a ground then) and put a variable
resistor from that common to ground. The output voltage should be
approximately 1.2 volts plus the resistance to ground in 100's of ohms.
E.g. 1K to ground should give close to 11.2 volts.

I've used several. One of my favorite for small currents uses a fixed
supply, about 18 volts unregulated. Then there's a series resistor that
limits the short circuit current to 220 ma. There's a simple shunt
regulator. A series resistor and a pot (probably 5 K pot) to ground. The
pot has a 15 volt zener to regulate its voltage. Then the emitter of a
PNP power transistor (could be germanium, I've used this supply since
about 1963) to the output +, collector to output - (or ground) and base
to the wiper of the pot. I suppose it could do more current with more
robust components. Or the circuit could be inverted to use a 2N3055 as
the shunt regulator emitter follower.

Take a look at the National Semiconductor linear regulator data book for
many more useful circuits.

73, Jerry, K0CQ
-- 
Entire content copyright Dr. Gerald N. Johnson, electrical engineer.
Reproduction by permission only.