Joe, I need a 3 volt Dc supply!!


Chief Journeyman
Jun 20, 2013
Kapiti Coast, New Zealand
Path under Coastlands overbridge
Then put a 1N4004 series diode on the output Lee if your application cannot tolerate that. Are you sure that is the issue? Cobalt Oxide based Lithium batteries usually charge at 4V and above which will be seen by your electronics. I assume this is a rechargeable application.

Another thought if it is just to much voltage, just put the 1N4004 in the battery output before the transmitter. That is your cheapest, easiest solution.

Clearly voltage regulation is not key to this application if it is running on a battery.
Recently, I converted electronic scales from running on expensive 3 volt lithium button cell battery with a low capacity to running on high capacity 3 x AA rechargeable ready to use nickel metal hydride cells in series. (3.6 volt)
I connected a 1N4001 diode in series to drop the voltage to approximately 3.0V and a 500mA PTC switch in series with the 1N4001 diode for short circuit protection.

This can be used in combination with the LM317 version of the Automatic Battery Charger for Boombox if required.
Set LM317 adjustable voltage regulator at 4.26 volts or slightly less for 3 x Low Self Discharge NIMH AA or AAA cells in series, with a 2.2 ohm resistor on the output to limit overcharge rate and prevent thermal runaway.
The LM317 version of this circuit has far better accuracy and thermal stability than the emitter follower version.

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