The following circuit amplifies a voltage by a factor (R1 / R2). What is important in this circuit is that it amplifies by almost exactly (-R1 /R2) so that the gain of the circuit can be controlled precisely by controlling the resistor values precisely.
Inverts and amplifies a voltage (multiplies by a negative constant)
- Zin = Rin (because V − is a virtual ground)
- A third resistor, of value
, added between the non-inverting input and ground, while not necessary, minimizes errors due to input bias currents.