0V in a schematic

[Eeyore]

"virtual ground" normally refers to a point which is maintained at
ground potential by feedback, e.g. the inverting input of an op-amp whose
non-inverting input is tied to ground.

But it may not be so simple.

Graham

 

[ian field]

But it may not be so simple.

Graham

A fun situation is the reference point of a mains powered SMPSU, usually
being the negative end of the bridge rectifier - makes quite a loud "pop" if
you accidentally ground it!

 

[Jamie]

---
**** you, Graham.

At least he's laying it all out so that we can see what he understands
and where he's weak so that those of us who care can help him along on
his way to enlightenment.

And you?

Instead of helping, you try to make him feel bad about himself by
insulting him.

Why would you do that?

Because he's ignorant? Which comes in various colors btw.




http://webpages.charter.net/jamie_5"

 

[Jamie]

Well, what I'm saying is that the input source is connected to GND, or a
point that we call 0V. The source is connected to one side of Rin. It's
essential that the other side of Rin is either connected to GND, or 0V
for the source to see it's being connected across Rin. With a virtual
ground arrangement, if the "earthy" one side of Rin got to be at 5V,
then source will not see Rin, but some other terminating value. That's
what I understand.

0 volts found in a circuit normally indicates the circuit's common
"COM" reference point to all other nodes of that circuit. It does not
mean how ever, that it would be a common to a remote circuit. when I
say remote, I refer to a device that allows external connection from
some other devices.

Hence, the 0V ref is a point to where all other nodes in that circuit
are in common with it.

Keep in mind that the "Common" supplied, for external/remote
connection does not have to be this same 0V ref, It could be a virtual
ground derived from this circuit or an isolated unit.

0V ref normally indicates a point of reference (com) for that circuit
and does not necessarily mean it's the global common.


And to confuse things more, a Virtual ground could also be the 0V ref
which would also be the common through out. This is normally found where
only a single stand alone rail supply is available, for example, a
battery or xformer with only 1 rail output. Both would offer isolation
from ground conflicts when connecting to external "common" sources, but
offer a way of creating a dual rail scenario to generate signals of +/-
with respect to ground/common.

assuming the (+)&(-) is from a single battery or Single rail isolated
supply.


(+)-------[1k]-------(V-Grnd/0V Ref)-------[1k]--------(-)



The above VG could be used as a common in an op-amp circuit while
the (+) and (-) terminals of our isolated single rail supply creates
the (+) and (-) rails with respect to the VG (virtual Ground) for the
Op-amp's Vcc and Vee supply terminals.


The resulting output of the op-amp could generate a true
+/- signal.

The only limitations of a VG, you need twice the voltage to obtain
the dual rail voltages..

12 Battery would yield 6V +/- for example minus the losses from other
things, we'll not get into.

http://webpages.charter.net/jamie_5"