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LM723 precision regulator:


LM327 is the old workhorse of the power supply industry. It includes precision regulation and over-current
protection on a 16 pin DIP. All the early big supplies used it, including Astron, Pyramid, Yaesu, Radio Shack,
etc. Occasionally they'd pop, so I kept a few on-hand in case. Most of the time they weren't in a chip
socket, so I'd add a socket when replacing them, in case it needed replacing again later.

These chips used a single (9.1v iirc) zener for reference, and could be selected to operate in either 0-7v
or 7-35v range. They could directly power a single 3055, or use that as a driver to run multiple 3055's for
a very high current capacity. If current was exceeded, they'd go into automatical fail-safe, usually tweeting
a beeper, and would reset automatically once the overload/short was removed. They didn't have any over-voltage
protection though, so this was usually added at the posts using a zener/resistor/SCR as a crowbar, usually set
to 15.0 volts. One time I had a pass transistor fail short, and the crowbar protected my radio, holding the
LM327 in overcurrent mode due to the scr's short, until I disconnected the shorted 3055.


LM723 precision regulator.pdf (470 KB)



last updated 11/30/2023 at 20:09:55