# What should be the output resistance of this source with series diode?

Below shows three sources with open terminals: simulate this circuit – Schematic created using CircuitLab

In Figure 1 if we want to calculate the output resistance, according to the linear circuit theory we short the voltage source V1 and look into the source and calculate the Thévenin equivalent. Hence for Figure 1 the output impedance is simply 100 Ohm.

What should be the way of thinking for the output impedance/resistance for Figure 2? If we know the current-voltage characteristic and the dynamic resistance of the diode D1 what does that indicate? Because if we short V2 and apply voltage to its terminals, because it is reverse biased the current will be close to zero and we will experience almost infinite resistance.

Does that mean in Figure 2 the output resistance is infinity? Or it is the dynamic resistance? How should be the way of thinking to derive the output impedance/resistance for the Figure 2 source?

• There is no constant output resistance of these circuits. They will have non-linear behavior depending on what they connected to. In case of ideal diodes you can speak of only two different "resistances". Jan 15, 2019 at 15:42 