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The concept of virtual ground allows us to approximate both input terminals of an op amp at the same potential. People say that both the terminals are 'shorted'. Do this mean that the current can flow between these terminals like they were really short circuited? Or this concept of 'shorting' is valid just for voltage equivalence at the two terminals?

Bhuvnesh
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The notion of a "virtual short" means that the voltages at the inverting and non-inverting op amp inputs are at the same voltage. This is true for an ideal op amp and a reasonably close approximation for a real op amp, provided that they are in a circuit with negative feedback and within their specified limits.

The virtual short does not allow current to flow between the two inputs. In an ideal op amp there is zero current into or out of either of the inputs.

jusaca
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Elliot Alderson
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The concept of a 'virtual short' is not complete without understanding feedback. An opamp without feedback cannot maintain a virtual ground.

In the picture below, Vp is equalized with Vn only through the output changing. If Vn is greater than Vp then the output will be adjusted down until Vp and Vn are equal (and vice versa if Vp is greater than Vn).

Very little current actually goes into the terminals, the terminals are high impedance in many modern opamps the current into the terminals is less than 1uA and sometimes in the pA range, in most cases, the current flowing into the terminals can be neglected because it is so small.

The current that does make a difference in changing the terminals value is the current from the output.

enter image description here
Source: https://www.dummies.com/education/science/science-electronics/analyze-noninverting-op-amp-circuits/

Voltage Spike
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  • Specifically, it is **negative** feedback that is required to create the virtual short. As shown in your example, the effect is better called a "virtual short" than a "virtual ground"...neither of the inputs is at ground. – Elliot Alderson Oct 15 '19 at 18:25
  • I've seen one amp that does not require negative feedback itself (but the outer loop does) – Voltage Spike Oct 15 '19 at 18:26