Question

The potential difference between the input terminals of an op-amp can be treated as nearly zero if:

• A. The two supply voltages are balanced
• B. The output voltage is not saturated
• C. The op-amp used in a circuit has negative feedback
• D. There is a DC bias path from terminals to ground

Hint:

For virtual short (i.e., \(V_+ \approx V_-\)), negative feedback must be present.

Answer 1

The Correct Option is C

In the context of operational amplifiers (op-amps), the potential difference between the input terminals can be considered nearly zero under specific conditions due to the properties of negative feedback. Here's the reasoning:

• Negative Feedback Principle: When an op-amp is used with negative feedback, it operates in a closed-loop configuration. This causes the op-amp to adjust its output to minimize the difference between its input terminals.
• Virtual Short Concept: In a negatively fed-back op-amp, the concept of a "virtual short" exists. This means that, although the input terminals are not physically shorted, the voltage difference across them is nearly zero due to the high open-loop gain striving to achieve equilibrium.
• Impact on Input Terminals: The high open-loop gain of the op-amp makes even tiny differences between the input voltages significant, resulting in a response that drives the inputs to the same potential, effectively rendering the potential difference negligible.

Thus, with negative feedback, an op-amp maintains this characteristic where the input terminals' potential difference is practically zero, confirming the correct answer:

The op-amp used in a circuit has negative feedback