Electronics > Beginners

Virtual ground circuit

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David Hess:

--- Quote from: aheid on January 10, 2019, 10:01:44 am ---I thought about mismatch between the regulators, but I wasn't sure about the implications.
--- End quote ---

There are improved replacements for the 317/337 from companies like Linear Technology (now Analog Devices) which would allow lower valued output resistors because of greater accuracy but they come with a premium price.  One of the old Linear Technology application notes discusses being able to use their regulators in parallel with just the circuit board resistance for current sharing.

spec:

--- Quote from: aheid on January 10, 2019, 10:01:44 am ---I got some MC34063's inbound, might try to create a voltage inverter with one of those. Though ideally I was hoping to avoid rolling my own SMPS for now (never done it before). From what I understand layout is important, breadboarding is a no-go, and I don't have the equipment for making custom PCBs yet. Can I do it by using prototyping PCBs?
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Very wise. :) Yes, because of the relatively low power involved, with care, you can make a decent SMPS with a prototype construction. 

One approach is to use a piece of copper clad fiberglass PCB and outline the unwanted copper with a scalpel. Then, any copper you wish to remove, just heat with the tip of a soldering iron and peel off. Conversely you can add traces/ground planes, by  aralditing  tinned copper wire (TCC) or copper foil to the PCB.

But, as you imply, it would be better to buy a ready made PSU.

soldar:
I cannot see the need (in general) for two OpAmps or that much complication. In its simplest form the attached circuit will do. If you need higher current sourcing or sinking then emmitter follower amplifier can follow.

spec:

--- Quote from: soldar on January 11, 2019, 01:13:25 pm ---I cannot see the need (in general) for two OpAmps or that much complication. In its simplest form the attached circuit will do. If you need higher current sourcing or sinking then emmitter follower amplifier can follow.
--- End quote ---
There are a few issues:

Most opamps will not be happy driving large capacitors.

The opamp maximum supply voltage and power dissipation limits the applicability.

None these rail splutters, provide a solid 0V. Just imagine using a class AB audio power amplifier with a rail splitter.

I am not sure how the frequency stability would work out if you did an analysis.

It is hard enough getting your 0V connections correct, even without the added complication of a rail splitter.

soldar:

--- Quote from: spec on January 11, 2019, 02:45:15 pm ---There are a few issues:

Most opamps will not be happy driving large capacitors.

The opamp maximum supply voltage and power dissipation limits the applicability.

None these rail splutters, provide a solid 0V. Just imagine using a class AB audio power amplifier with a rail splitter.

I am not sure how the frequency stability would work out if you did an analysis.

It is hard enough getting your 0V connections correct, even without the added complication of a rail splitter.

--- End quote ---
Well, I agree that it is better to have a split power supply and not need a rail splitter but this thread is about using a splitter for whatever reasons.

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