Inverting and non-inverting amplifiers
An inverting amplifier applies the input signal to the negative terminal and returns feedback from the output to the same terminal, producing an output that is the input multiplied by a negative gain (inversion plus amplification). A non-inverting amplifier applies the input to the positive terminal, producing an output with positive gain. Both gain values are set by choosing feedback and input resistor ratios. The difference is whether the signal is flipped; inverting gives more flexibility for combining signals, while non-inverting has higher input impedance.
Summing, differentiating, and integrating circuits
A summing amplifier (inverting with multiple inputs) adds up all input voltages weighted by their input resistors, useful for mixing audio or combining sensor signals. A differentiator has a capacitor in the feedback path instead of a resistor, producing an output proportional to the rate of change of the input (derivative). An integrator reverses this, accumulating input voltage over time (integral). Differentiators amplify high-frequency noise badly, so they usually include a resistor in series with the capacitor to limit high-frequency gain. These building blocks form the analog side of mixed-signal systems.