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[SOLVED] Rail splitter / virtual ground using an audio amp?

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hughmanoid

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HAS ANYONE USED LM380, LM383, LM384, LM390, LM2002 ETC TO MAKE A RAIL SPLITTER ?

Typical VCC can go as high as 20 to 22 vdc for some of the chips.
No signal, no gain, just inputs pulled low and or tied together.

I would like to drive an Nfet or IGBT +15 or less and -15 or ''more'' (positive) for hard switching.
Rigging up an ISOLATED high side driver with DUAL SUPPLIES looks to be a pain.
Would also like to stay away from bootstrapping and have SOLID gate drive pulses.

I think I need a virtual ground on the source/emitter and After looking at several rail splitters and op amps that only sink/source 20 to a few hundred ma. I saw some discrete designs with npn and pnp totem pole (?) output.

Since these audio amps have the quiescent output at 1/2 VCC and should be able to source and sink current, I think grounding the inputs so all the output has to do is fight to keep the output at 1/2 VCC seems like it would work. Worst case is I may need to add a boost smps to boost to 22 volts or so with my virtual ground at 9 volts and 13 more volts or so to mash the gate/base on.

The fet will hopefully bucking 450 volts down to 165 volts to feed a modified sine inverter using two half bridge igbt modules as an H bridge to create a noisy dirty simulated 120VAC at hopefully a kilowatt (plus or minus 1 kilowatt). If that works I may try to simulate a true sine inverter...

Brian In santa cruz
 

Frequently.

Just wire for unity gain (make sure the device you choose is unity gain stable) and use two resistors of the same value to incoming -Ve and to incoming +ve, connected to the amplifiers non-inverting input.
Use the amplifier output as ground and the original +/- as the two supply rails. The biggest problem you will have is stability, remember that the amplifier will almost certainly have to drive directly into decoupling capacitors and most can't drive a heavily capacitive load. You might need resistors in the + and - lines to isolate the capacitive load.

Brian.
 
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