I am having trouble understanding the difference between these two concepts. I know that input resistance is the resistance looking into the input terminals and output is looking into the output terminals. What I don't understand is how to evaluate these. In the image below, are the input and output resistances simply the Thevenin resistances at the input and output terminals?
- Disconnect the source. Calculate the equivalent resistance seen across the open terminal Vi. That's Ri.
- Disconnect the load, as well as short the voltage source (prefect voltage sources have zero resistance). Calculate the equivalent resistance seen across the open terminal Vo. That's Ro.