Non-Inverting Gain

A non-inverting op-amp uses negative feedback to force the inverting input to sit at nearly the same voltage as the non-inverting input. Because the op-amp input current is ideally negligible, the feedback network acts like a simple voltage divider from the output to ground, so the output must rise until the divider voltage matches the input. Solving that divider relationship gives the closed-loop gain A_v = 1 + R_f/R_in, with the key feature that the output stays in phase with the input.

Use this when you need an op-amp stage that amplifies a signal without inverting its polarity, such as sensor conditioning, buffer-amplifier stages, and audio preamps. It is especially useful when you want a high input impedance and a predictable gain set by two resistors.

• Swapping R_f and R_in, which gives the wrong gain
• Forgetting the +1 term and using only R_f/R_in
• Using this formula for an inverting amplifier, where the sign and circuit behavior are different