What is the difference between real ground and virtual ground in opamp?

I understand what a real ground for a Opamp is.It is a terminal which is physically connected to ground or earth which acts as the reference point for the entire circuit.

But what do we mean by a virtual ground?

And how do we explain it with the help of opamps?

And finally is my understanding of real ground correct or is there something more specific that i can add.

• They call it virtual ground because it is not directly connected to ground. Virtual ground is only kept at 0V by op-amp feedback. Certain assumptions have to remain true in order for it to be a virtual ground, one of which is that the op-amp is used with negative feedback. Apr 24, 2020 at 19:14
• Take a look here electronics.stackexchange.com/questions/441184/…
– G36
Apr 25, 2020 at 7:32
• Virtual, in this sense, means 'almost, but not exactly'.
– Chu
Apr 26, 2020 at 0:32

In the context of an op-amp circuit, ‘real’ ground is the common zero-volt referenced to the power supplies and rest of the system.

‘Virtual’ ground is a reference used for op-amp signals that represents a signal zero-volt reference.

Virtual ground comes up mainly when using a single-ended supply with an op-amp. In order to represent signals that have negative and positive swing, the op-amp’s input and output signals need to be offset so that they fit between ‘real’ ground connected to -V, and positive supply connected to +V.

So most often, a low-impedance midpoint reference is used as ‘ground’ to give the desired offset to the op-amp.

In fact the virtual ground can be any offset with respect to real ground (including no offset). What makes it virtual is that it’s a driven, low-impedance signal reference and not a direct connection to any ground or supply voltage.

• We can explain this by infinite voltage gain too? Apr 25, 2020 at 5:13

Virtual ground means a node that has the same potential as ground but is not passively or inherently equal ground. i.e. a point that is actively being driven to be equal to ground.

Ground by definition is a ZERO VOLT REFERENCE. Earth Bonding is a common 0V reference while in electronics it can be floating.

Op Amps use negative feedback to force the difference input to become near zero and drive the output in the linear region. So we call the differential null input a virtual ground. Often Vin+ also goes to GND so Vin- must also be near 0V but that's only by design choice.