Changing Feedback Ratio Changes Gain - Electronic Circuits VI: Op-Amp Feedback and Exact Gain Networks Step by Step

Changing the feedback resistor changes the exact inverting gain. 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 fraction current stays exact

The 1 volt input across 2 ohms gives one half ampere.

I = \tfrac{1}{2}\ \text{A}

Changing only the feedback ratio changes gain

With 8 ohms in feedback, the output is -4 volts.

V_{\text{out}} = -\left(\tfrac{1}{2}\ \text{A}\right)\cdot 8\ \text{ohm} = -4\ \text{V}