Follow the wire.
Understand the node.
Two real circuits. One idea: connectivity comes before the calculation.
A node is more than a dot.
Follow each uninterrupted conductor. Every point on it belongs to the same electrical node, whether the drawing includes a dot there or not. A resistor sits between two different nodes.
Start at VIN, cross R1 to the output, then cross R2 to the ground reference. These are three nodes, not three junction dots. VIN and VOUT are ports; no voltage source is hidden in this drawing.
The host owns selection, theme and values. Hover or focus previews a node; the SVG download keeps only your saved selection.
- VIN and R1.a share the input node. VIN is a terminal, not a drawn voltage source.
- R1.b, R2.a and VOUT share one output node, including the branch to VOUT.
- R2.b connects to GND, the reference node. R2 separates this conductor from B.
All nets shown. No selection.
Near ground is not wired to ground.
The summing node B connects the input resistor, feedback resistor and inverting input. The ground node D connects the noninverting input. There is no wire between B and D.
“Virtual ground” describes an ideal operating condition under negative feedback, not an extra connection. Follow RF from C back to B and compare it with the separate supply nodes E and F.
This second figure has its own selection. Changing it never changes the divider above. All six labels remain available by keyboard.
- VIN connects to RIN.a. RIN separates the input node from the summing node.
- RIN.b, RF.a and U1.inverting share the summing node. It is not wired to GND.
- U1.output, RF.b and VOUT share the output node. RF returns feedback to B.
- U1.noninverting connects to GND. This reference node is distinct from B.
- VPLUS connects to U1.vplus, the positive supply pin, not the signal input.
- VMINUS connects to U1.vminus, the negative supply pin, not the inverting input.
All nets shown. No selection.