What does the concept of a virtual short imply in an op-amp circuit with negative feedback?

What does the concept of a virtual short imply in an op-amp circuit with negative feedback?

• A. The input voltages are equal (approximately)
• B. The output equals the input
• C. The input voltages differ by a large amount
• D. The op-amp saturates if there is no feedback

Answer: (A)

Virtual short means the two input terminals of an op-amp sit at essentially the same voltage when negative feedback is present. Because the open-loop gain is enormous, the output moves to drive the difference between the noninverting and inverting inputs toward zero. So V+ is approximately equal to V-, even though there isn’t a real wire connecting them. This makes the input node at the inverting input behave like a near-ground (virtual ground) node in many configurations, simplifying analysis. It’s important to remember the equality is in voltage, not a physical short, and a tiny input current can still flow. The concept relies on negative feedback; without it, the inputs wouldn’t be forced to be equal and the output could saturate.

Virtual short means the two input terminals of an op-amp sit at essentially the same voltage when negative feedback is present. Because the open-loop gain is enormous, the output moves to drive the difference between the noninverting and inverting inputs toward zero. So V+ is approximately equal to V-, even though there isn’t a real wire connecting them. This makes the input node at the inverting input behave like a near-ground (virtual ground) node in many configurations, simplifying analysis. It’s important to remember the equality is in voltage, not a physical short, and a tiny input current can still flow. The concept relies on negative feedback; without it, the inputs wouldn’t be forced to be equal and the output could saturate.