WIP: describe a set of op-amp circuits that can do +, -, *, integrate, differentiate
Throughout this page, $V_i$ denotes input voltage, $V_o$ denotes output voltage, $R_f$ denotes feedback resistor.
Check if v_out < v_in or v_out > v_in.
Multiply by 1. Why is this useful? It prevents loading, and separates stages of a circuit. Can also supply more current than the original voltage source allows.
Multiply by positive number
$$ v_o = \left(1 + \frac{R_f}{R_1}\right) v_i $$
Multiply by negative number (wow no way)
$$ v_o = -\frac{R_f}{R_1} v_i $$
Secretly the same circuit as non-inverting amplifier — swap the voltage sources at the + and - inputs!!
relies on KCL to add (scaled) voltages.
Uses 4 resistors: inverting config + 2 resistors as voltage divider into + terminal. If we “match” values of pairs of resistors,
$$ v_o = \frac{R_f}{R_1} (v_+ - v_-) $$
Otherwise the transfer function is a little more complex (coefficient of $v_+$ involves all 4 resistor values)