Loaded Node Before Gain - Electronic Circuits V & VI: Front-End Conditioning and Op-Amp Feedback Step by Step

This loaded-node-before-gain lesson applies ideal gain to the node that actually reaches the amplifier, not to the unloaded source voltage. The 6 V source loading down to 3 V, then gaining by 2 to 6 V, is exact only for the stated ideal divider-plus-gain rows. Real front ends add finite input impedance, bias current, bandwidth limits, offset, settling error, noise, calibration limits, and measurement uncertainty.

An ideal gain contract multiplies the loaded node, not the open source voltage. Exact arithmetic here means exact results for the stated model inputs; measured inputs still carry uncertainty and significant-figure limits.

highlighted = computed this step

The gain stage receives the loaded node

The source is 6 volts, but the input node is only 3 volts after loading.

V_{\text{in}} = 3\ \text{V}

The ideal gain multiplies the loaded node

The declared gain of 2 acts on the loaded input, giving 6 volts.

V_{\text{out}} = 2\cdot 3\ \text{V} = 6\ \text{V}