## Working principle

The inverting amplifier configuration produces an output voltage equal to its input voltage multiplied by a negative ratio of its two resistors:

### Formula derivation

Since any ideal op-amp tries to keep its two terminals at an equal voltage, the inverting input of the op-amp (V_{-}) is at the same potential as the non-inverting terminal (V_{+}) and, thus, forms a virtual ground at its node: V_{-} = V_{+} = 0.

Since the op-amp’s input terminals (V_{+} and V_{-}) have an infinite input impedance, there is no current flowing into them. Instead, all of the current flowing through R_{1} also flows through R_{2}:

### Experiments

- Vary the input voltage and resistor values and observe the change at the output.
- Change the input voltage to a negative value and verify that the output voltage is now positive (inverted).
- Make R
_{1}and R_{2}equal to create an inverting buffer. What is the output voltage now in terms of the input voltage?