pseudo ground generation

[[email protected]]

I'm curious what people are doing for the pseudo ground (mid-rail) in
single supply analog circuits. Simple resistor divider? Divider
buffered with amp? LDO?

 

[Eeyore]

I'm curious what people are doing for the pseudo ground (mid-rail) in
single supply analog circuits. Simple resistor divider?

I've done that in the past for sure. Plus a large cap to ground.

Divider buffered with amp?
Ditto.


LDO?

TI make dedicated ICs for this purpose.

Why not use a split supply though ?

Graham

 

[Fred Bloggs]

I'm curious what people are doing for the pseudo ground (mid-rail) in
single supply analog circuits. Simple resistor divider? Divider
buffered with amp? LDO?

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.

 

[Eeyore]

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.

WhooossshhhHHH

Graham

 

[Vladimir Vassilevsky]

I'm curious what people are doing for the pseudo ground (mid-rail) in
single supply analog circuits. Simple resistor divider? Divider
buffered with amp? LDO?

TLE2426


Vladimir Vassilevsky
DSP and Mixed Signal Design Consultant
http://www.abvolt.com

 

[John Devereux]

I'm curious what people are doing for the pseudo ground (mid-rail) in
single supply analog circuits. Simple resistor divider? Divider
buffered with amp? LDO?

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.

 

[[email protected]]

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.

 

[john jardine]

[...]

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.

 

[Jamie]

I'm curious what people are doing for the pseudo ground (mid-rail) in
single supply analog circuits. Simple resistor divider? Divider
buffered with amp? LDO?

You can get small package virtual grounds or make one via an op-amp
etc..
http://tangentsoft.net/elec/vgrounds.html

 

[John Larkin]

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

That's what I call Fred!


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

John

 

[Nemo]

John Devereux suggested...

It depends on the application - for me it often ends up being a
resistive divider with bypass cap. ....
in fact often you
can use the 2.5V reference of an ADC or microcontroller

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.