In a non-inverting summing amplifier, what is the differential input voltage in linear operation?

In a non-inverting summing amplifier, what is the differential input voltage in linear operation?

• A. 5 V
• B. -5 V
• C. 0.7 V
• D. 0 V

Answer: (D)

In linear operation with negative feedback, the op-amp adjusts its output to make the voltages at its two input terminals as close as possible. In an ideal op-amp, that means they are exactly equal, so the differential input voltage is zero. In a real amplifier with finite open-loop gain, the difference is V+ − V− = Vout / A, which is still extremely small when the device is operating in its linear region. For a non-inverting summing amplifier, the negative feedback enforces V− to track V+, so the differential input voltage remains essentially 0 V.

In linear operation with negative feedback, the op-amp adjusts its output to make the voltages at its two input terminals as close as possible. In an ideal op-amp, that means they are exactly equal, so the differential input voltage is zero. In a real amplifier with finite open-loop gain, the difference is V+ − V− = Vout / A, which is still extremely small when the device is operating in its linear region. For a non-inverting summing amplifier, the negative feedback enforces V− to track V+, so the differential input voltage remains essentially 0 V.