Opamp Models and Resistive Circuits
Robert O'Rourke · 2024
Operational amplifiers (opamps) are common circuit building blocks in electronics. This chapter focuses on some of the most simple and common opamp models. The ideal opamp modeling notion of zero voltage between two pins, with no current flowing, defies our normal electronics notion of a short circuit that allows any amount of current to flow. A different way to describe the ideal opamp model, and its infinite gain, is that the output will be whatever it needs to be in order to keep the input voltage zero. An opamp can be modeled as a controlled voltage source. This controlled-source opamp model can be implemented in SPICE, or other lumped element circuit simulation using a voltage-controlled voltage source circuit element. Using the ideal opamp model, the inverting amplifier would work regardless of which opamp terminal was connected to the resistors.