Feedback Gain Cross Scans

Inverting Gain Three-Row Scan

feedback resistance sets output

Holding input current fixed makes the inverting gain relationship visible across three rows. Exact arithmetic here means exact results for the stated model inputs; measured inputs still carry uncertainty and significant-figure limits.

highlighted = computed this step

Equal resistors give unit inverting gain

The input current is 1 ampere. With feedback resistance 2 ohms, the output is -2 volts.

Vout=−(1 A)⋅2 ohm=−2 VV_{\text{out}}=-\left(1\ \text{A}\right)\cdot2\ \text{ohm}=-2\ \text{V}
Inverting gain scan rowThe feedback resistor converts the same current to output voltage.+-op amprails -12 V to 12 VVout -2 VV+ 0 VV- 0 VI+ 0 AI- 0 ARin 2 ohmIin 1 ARf 2 ohmIf 1 AV+ = V-inverting

More feedback resistance makes more negative output

The input current stays 1 ampere, while feedback resistance rises to 4 ohms. The output becomes -4 volts.

Vout=−(1 A)⋅4 ohm=−4 VV_{\text{out}}=-\left(1\ \text{A}\right)\cdot4\ \text{ohm}=-4\ \text{V}
Inverting gain scan rowOnly the feedback resistor changed.+-op amprails -12 V to 12 VVout -4 VV+ 0 VV- 0 VI+ 0 AI- 0 ARin 2 ohmIin 1 ARf 4 ohmIf 1 AV+ = V-inverting

The same current gives a third output point

The final row keeps the input side fixed and uses 6 ohms in feedback. The output is -6 volts.

Vout=−(1 A)⋅6 ohm=−6 VV_{\text{out}}=-\left(1\ \text{A}\right)\cdot6\ \text{ohm}=-6\ \text{V}
Inverting gain scan rowThree exact rows show output proportional to feedback resistance.+-op amprails -12 V to 12 VVout -6 VV+ 0 VV- 0 VI+ 0 AI- 0 ARin 2 ohmIin 1 ARf 6 ohmIf 1 AV+ = V-inverting