Stiff Versus Weak Source - Electronic Circuits III: Comparators and Interfaces Step by Step

Changing source resistance changes the same load voltage by exact divider arithmetic. Exact arithmetic here means exact results for the stated model inputs; measured inputs still carry uncertainty and significant-figure limits.

highlighted = computed this step

A lower source resistance holds more load voltage

With source resistance 2 ohm, the load gets 12 volts.

V_{L,\text{stiff}} = 12\ \text{V}

A higher source resistance loses more voltage

With source resistance 10 ohm, the same load gets 6 volts. Reactive impedance and frequency response are deferred.

V_{L,\text{weak}} = 6\ \text{V}