76-op-amp-inverting-simulation

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Inverting amplifier realized with op-amp is given in figure bellow.

Simulate op-amp inverting amplifier.

inverting-op-amp-amplifier

Input impedance is not very high, comparing to non-inverting amplifier. Actually, input impedance is equal to R2, since input voltage source must provide current that is reverse proportional to R2.

Output voltage is in opposite phase with input voltage (phase shift is 180 degrees). Since voltage amplification of operational amplifier is very high, and negative feedback is applied, inputs in operational amplifier can be treated as V+=V, since V+ is on the ground and V is on the virtual ground.

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:

inv_op_amp_eq_01

added to potential of voltage divider from input voltage

inv_op_amp_eq_02a

Due to virtual ground:

inv_op_amp_eq_03b

Voltage gain is

inv_op_amp_eq_04

  • 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=0V, so

inv_op_amp_eq_05

Final result for voltage gain is the same:

inv_op_amp_eq_04

Go to op-amp inverting amplifier simulation.

External links:

Inverting Op-amp Amplifier on All about circuits

Inverting Op-amp Amplifier on electronics-tutorials

Inverting Op-amp Amplifier on Hyperphysics

 

 

 

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