If a positive voltage is applied to the input of a noninverting op amp, the output voltage is

If a positive voltage is applied to the input of a noninverting op amp, the output voltage is

• A. Negative
• B. Positive
• C. Zero
• D. Undefined

Answer: (B)

A noninverting amplifier drives its output in the same phase as the input because the feedback network provides a positive, in-phase gain. With a positive voltage at the noninverting input, the op-amp adjusts its output upward so that the inverting input, which is connected to a portion of the output, matches the positive input voltage. In linear operation, this means the output must be positive as well. Only if the device is unpowered or the output hits the supply rails would you see saturation or undefined behavior; under normal conditions the output remains positive.

A noninverting amplifier drives its output in the same phase as the input because the feedback network provides a positive, in-phase gain. With a positive voltage at the noninverting input, the op-amp adjusts its output upward so that the inverting input, which is connected to a portion of the output, matches the positive input voltage. In linear operation, this means the output must be positive as well. Only if the device is unpowered or the output hits the supply rails would you see saturation or undefined behavior; under normal conditions the output remains positive.