inverting amplifier
The inverting amplifier is a basic circuit of the operational amplifier. In the inverting amplifier, the positive input is to ground and the signal input is the negative input, which is connected to the output through a feedback resistor.
The gain of the inverting amplifier is given by the ratio of the feedback resistor (R2) to the resistor (R1) in the input circuit, R2/R1. If both resistors are equal, the gain is 1, but since the minus input is used for the input signal, signal inversion occurs and the polarity of the output signal is the reverse of that of the input signal.
Since resistor R1 is in series with the source impedance, unwanted noise increases at low signal levels.