[R-390] OT: Pass Transistor Question
Barry
n4buq at knology.net
Tue Oct 14 20:18:52 EDT 2008
A few weeks ago, I mentioned I wanted to build a regulated, low-voltage
power supply that uses an LM317 with some pass transistors to enable it to
handle a larger current than the LM317 can handle. The circuit uses a
2N2905 to drive a 2N3055 in a "pass transistor" configuration around the
LM317 and the circuit description states it's capable of delivering up to 3
amps in this configuration.
I have a transformer with a 6-amp capacity and I would like the power supply
to deliver up to 5 (maybe all 6 amps) if I want. Is it possible to put
another 2N3055 in parallel with the one in the circuit allowing thus
allowing the pass transistors to deliver the extra amperage. Will this
work?
I ran across something like it here:
http://ourworld.compuserve.com/homepages/Bill_Bowden/page12.htm
(Scroll down to the middle of the page). The two 2N3055s are paralled and
have 0.1-ohm resistors in the emitter lines. Not sure what these equalizing
resistors do, but perhaps that's all I need to add?
By the way, the original circuit is on page 127 of the 1978 ARRL handbook.
Thanks guys for the OT help.
Barry
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