The term describing equal voltages at the inputs due to feedback is?

The term describing equal voltages at the inputs due to feedback is?

• A. Virtual ground
• B. Open loop
• C. Saturation
• D. Virtual short

Answer: (D)

When an op-amp is in a configuration with negative feedback, the amplifier’s high gain drives the input voltages to become nearly the same. The output adjusts itself so that the difference between the noninverting and inverting inputs is pushed toward zero. Because of this, the two input terminals act as if they are connected by a very small short, even though no real conductor ties them together. This is called a virtual short. It’s important to note that it’s not a real short and no current flows between the inputs; the op-amp input currents are still typically very small due to high input impedance. A related term, virtual ground, is a special case where one input is at zero volts, which can occur in certain configurations like the inverting amplifier. The other options describe different situations: open loop means no feedback and typically large input difference, and saturation means the output has swung to the supply limits, neither of which describes the equal-input condition. In real devices the equality is approximate, since the gain is finite, but in standard negative-feedback analysis the virtual short assumption holds well.

When an op-amp is in a configuration with negative feedback, the amplifier’s high gain drives the input voltages to become nearly the same. The output adjusts itself so that the difference between the noninverting and inverting inputs is pushed toward zero. Because of this, the two input terminals act as if they are connected by a very small short, even though no real conductor ties them together. This is called a virtual short. It’s important to note that it’s not a real short and no current flows between the inputs; the op-amp input currents are still typically very small due to high input impedance. A related term, virtual ground, is a special case where one input is at zero volts, which can occur in certain configurations like the inverting amplifier. The other options describe different situations: open loop means no feedback and typically large input difference, and saturation means the output has swung to the supply limits, neither of which describes the equal-input condition. In real devices the equality is approximate, since the gain is finite, but in standard negative-feedback analysis the virtual short assumption holds well.