Non Inverting Operational Amplifier


In this configuration, the input voltage signal, \(\) is applied directly to the non-inverting (+) input terminal(Pin 3 of OPA336) which means that the output gain of the amplifier becomes positive.
Feedback control of the non inverting operational amplifier is achieved by applying a small part of the output voltage signal back to the inverting (-) input terminal via \(\) voltage divider network, again producing negative feedback. This closed-loop configuration produces a non-inverting amplifier circuit with very good stability, a very high input impedance \(\) approaching infinity(in ideal conditions no current flows into the positive input terminal) and a low output impedance \(\) (\(\) in ideal conditions).

For an ideal Operational Amplifier no current flows into the input terminal and then, the potential of inverting terminal \(\) is always equal to the non-inverting\(\) one. \(\) & \(\) form a simple potential divider network across the Op-Amp with the voltage gain of the circuit being determined by the ratios of \(\) and \(\).

Then using the formula to calculate the output voltage of a potential divider network, we can calculate the closed loop voltage gain \(\) of the non-inverting amplifier as follows:

\(\) and for the Ideal Summing Point, we have \(\). The voltage gain is equal to \(\) and combinig the previus equations we get:


We can see from the equation above, that the overall closed-loop gain of a non-inverting amplifier will always be greater but never less than one, it is positive in nature and is determined by the ratio of the values of \(\) and \(\).
If the value of the feedback resistor \(\) is zero, the gain of the amplifier will be exactly equal to one. If resistor \(\) is zero, the gain will approach infinity, but in practice it will be limited to the operational amplifiers open-loop differential gain, \(\).

Best regards, ecasa.