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I have an old laptop power supply that outputs 15vdc at 3amps.
Will your suggested circuit above work for a 12 vdc lead acid battery? I want to regulate its voltage since it spikes up to 17 to 18 volts. I want to have a regulated 12 vdc 500ma - 1 A source.
Dropout voltage of the LM7812 is 2.5V minimum!(minimum = "when the sun is shining and you are going downhill").You should never go that low, keep at least 3V overhead or suffer on line and load regulation as well as output noise and ripple.
This is for a high voltage programming of AVR circuit btw..
What is the difference between a 2N3903 and a 2N3904?
He doesn't need a tightly regulated 12.0V line for that. A volt or two out of range will be fine. My programmer's high voltage line is 13.something volts. Double check the datasheet for the acceptable range of Vpp.
With the circuit above I was able to get 11.86vdc...still not quite 12vdc, any way to bump it up a little more?