Non inverting amplifier realized with op-amp is given in figure bellow.
Simulate Op-amp non inverting amplifier.
Input impedance is very high, since the overall input impedance of a closed-loop non inverting amplifier configuration is:
In here, AOP-AMP is open loop gain of operational amplifier that is very high (usually higher then 106), Î² is feedback gain, and ZOP-AMP is input impedance of op-amp that is also very high. Output voltage is in phase with input voltage. Since voltage amplification of operational amplifier is very high, inputs in operational amplifier can be treated as if there are on the same electrical potential, i.e. V+=V–
Voltage gain can be calculated in two ways:
- By combining superposition theorem and node potential of input and output terminal.
Potential of inverting input can be calculated as voltage divider from output voltage:
On the other hand, due to V+=V–
Voltage gain is
- By equaling currents.
Since currents that flow from/to operational amplifier input can be neglected, current through R2 is equal to current through R1. Then, again V+=V–, so
Final result for voltage gain is the same: