pseudo ground generation

Gnd is gnd for single supply amps, there is no pseudo ground...seems a bit late in the game to be confused by this elementary issue.

TLE2426

Vladimir Vassilevsky DSP and Mixed Signal Design Consultant

It depends on the application - for me it often ends up being a resistive divider with bypass cap. (By the way watch out for microphony in ceramic capacitors when doing this - tantalums seem OK though).

I think Fred is probably right, in that it usually does not help to think of it as "ground". I usually call it "ref", in fact often you can use the 2.5V reference of an ADC or microcontroller, or sometimes half of this.

Well, that's why I called it "pseudo." ;-)

I've used the TI chip Vladimir mentioned, but was wondering what people who do volume board products do.

Thanks all for the comments.

For opamp mid rail biasing etc, two resistors and a cap are fine. Only need an opamp (=cost) low R output in wholly DC arrangements.

You can get small package virtual grounds or make one via an op-amp etc..

That's what I call Fred!

Check out the LM8261. It's not especially cheap, but it can sure drive a bypassed rail.

John

John Devereux suggested...

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I would advise against this latter idea as they act like simple linear voltage regulators. Thus they can source current and pull UP to 2.5V, but in a micropower circuit, cannot SINK current if RFI pumps energy in and raises their output above 2.5V. So, unless there is a significant load (say 2mA) on their output, mobile phones and suchlike in the vicinity make your readings go awry.

In micropower / cost sensitive circuits, I've found that an op-amp-buffered resistive divider with two 100k resistors provides a much stabler ref rail than the 1.5V or 2.5V ref from a microcontroller, when there's RFI around.