Operational amplifiers

Operational amplifiers

An op-amp amplifies the difference between its two inputs with a huge open-loop gain, so on its own it acts as a comparator. Negative feedback through resistors sets a precise gain: inverting $-\frac{R_f}{R_{in}}$, non-inverting $1+\frac{R_f}{R_1}$. The output can't go beyond the supply voltages (saturation), and gain × bandwidth is roughly constant.