noninverting

Noninverting describes an amplifier configuration in which the input signal is applied to the noninverting input of an operational amplifier. The output is in phase with the input, unlike inverting configurations where the output is inverted by 180 degrees. In many contexts, noninverting denotes a stage where feedback preserves the input’s polarity.

In a typical noninverting op-amp amplifier, the input is connected to the + input. Feedback is provided from the output to the - input via a resistor network consisting of R1 from the - input to ground and R2 from the output to the - input. The closed-loop gain is 1 + R2/R1. A unity-gain configuration (voltage follower) is achieved by placing the output directly to the - input (R2 = 0).

The noninverting configuration offers very high input impedance, because the signal is fed into the op-amp input. This makes it suitable for buffering and interfacing with high-impedance sources. However, the gain is limited by the op-amp’s open-loop gain and finite bandwidth; the product of closed-loop gain and bandwidth is approximately constant (gain-bandwidth trade-off). Real devices also introduce offset voltage and input bias currents, which can contribute to output errors.

Applications include signal amplification with minimal phase distortion, sensor conditioning, active filters, and audio preamplification. Compared with inverting stages, noninverting amplifiers have higher input impedance and noninverting gain, at the cost of potentially higher noise and lower stage isolation in some designs.

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