At 07:54 AM 01/04/2003 -0500, you wrote:
>Another common practice, as long as your normal load is constant and the
>source is somewhat stable, is to put a resistor across the input and
>output to take some of the primary task off the 7805. The peak loads
>will be handled by the regulator. This is only effective if you run the
>numbers. Calculate your resistor value by taking your average
>unregulated voltage and average load current. Increase the resistor
>value somewhere between 10 and 30%. (This may vary and depend upon
>unregulated voltage and load current.)

Another common solution is to put a smallish resistor on the input to the
7805, and a PNP transistor across the whole lot.

Emitter goes to resistor input,
Base goes to resistor, regulator input junction,
Collector goes to regulator output.

Not sure what size of resistor you need to put there, but it will make a
difference, and depends on the Hfe of the transistor.

--Brendan

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