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Inverting Amplifier

In an inverting amplifier the signal enters through a resistor $R_{in}$ to the negative input, while the feedback resistor $R_f$ runs from the output back to the same input. The gain is negative, so it inverts the signal (180° phase shift), and is set only by the ratio of the two resistors.

A=-\dfrac{R_f}{R_{in}}

voltage gain, inverting amplifier

Symbols

$R_{in}$	input resistor	$\Omega$
$R_f$	feedback resistor	$\Omega$
$A$	voltage gain

Example

$R_{in}=1$ kΩ, $R_f=10$ kΩ, $V_{in}=0.2$ V:

$V_o=-10\cdot0.2=-2$ V.

The minus sign means a 180° phase shift – do not forget it when computing the output.

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Part of Electronics: Operational amplifiers.