John Pearson wrote:
> I have a 5v voltage regulator where the data sheet states the
> absolute maximum input voltage is 9v DC. I want to use transistor
> batteries on it and the voltage that the regulator sees on the input
> side, with the full circuit operating, with a new battery, is about
> 9.2 - 9.3 volts.
>
> I don't want to slip-in a diode because I want to get the maximum
> life out of the battery without a voltage drop penalty.
>
> What do you think. Am I looking for trouble?

Tell us how much current you need to draw.  Unless you need the 9V for
something else in the circuit, you are going to waste nearly half of
your usable battery by heating the regulator.  Perhaps you could use a
low dropout regulator and 4 or 5 AA's or AAA's.  Or design the circuit
to run at lower voltages (if possible) and skip the regulator all
together.  Maybe a switching regulator would be worthwhile considering?

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