Can you drive two rails from one transformer output?

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u mean voltage doubler?
yes ,ii will work .
but the output voltage will be half wave rectified ,soits not that "clean"
to drive an op amp (if its amplifiying audio signals) u'll need to use some heavy filtering ...🙂
 
There is a way, half wave using 2 diodes. If current is not high, you won't get problems in getting a clean output with reasonable capacitance.
- Use one of the outputs as GND
- Connect the other output to the anode of one diode (its cathode is the positive output) and to the cathode of the other diode (its anode is the negative output).
- Connect at least 1000uF capacitor in parallel with each output, to GND.

This worked for me in a switching power supply, at 80KHz but the principle is just the same, but you need more filtering.
 
What DC rails are you after?

Rectification of 14VAC (whichever way you do it) gives you 19.75V DC minus the volt drop of the recitifier. Rectifiers typically drop 1.1V to 1.5V. You want complimentary rails so I'd sugest a virtual earth circuit (google it for more detail).

A good virtual earth is basically a resistor divider pair in series across the supply (giving you half of your DC supply at the mid point) feeding a non-inverting unity gain opamp (to handle current through the virtual earth).


Sam.
 
samborambo said:
What DC rails are you after?

A good virtual earth is basically a resistor divider pair in series across the supply (giving you half of your DC supply at the mid point) feeding a non-inverting unity gain opamp (to handle current through the virtual earth).


Sam.

Good in theory, but only works when the supply loads are reasonably balanced; any difference greater than the op-amp Iout(max) causing the rails to shift.

But I know you knew that 😉
 
sss said:
u mean voltage doubler?
yes ,ii will work .
but the output voltage will be half wave rectified ,soits not that "clean"
to drive an op amp (if its amplifiying audio signals) u'll need to use some heavy filtering ...🙂


good rejection linear regulator/amplifier to drop each side to 12V. Add a series current source/limiters, and you have a great balanced PS for Op-amps.🙂
 
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