inverting amplifier is One of the more popular circuit configurations of the op-amp, because of its simplicity, shown in below Figure .
The input signal to be amplified is connected to the inverting terminal, while the noninverting terminal is grounded. It will now be shown how it is possible to choose an (almost) arbitrary gain for this amplifier by selecting the ratio of two resistors. The analysis is begun by noting that at the inverting input node, KCL requires that
The current iF , which flows back to the inverting terminal from the output, is appropriately termed feedback current, because it represents an input to the amplifier that is “fed back” from the output. Applying Ohm’s law, we may determine each of the three currents