DC voltage source

The textbook DC voltage source: a circle with a plus and a minus, and the voltage you set. Aliases: DC power supply, VDC, ideal source, dual supply.

Unlike the Power flag (vcc), which is a rail with ground implied, this is a two-terminal source that floats. V+ is held the set voltage above V-, wherever V- is wired. Two in series, with ground between them, make a split supply of plus and minus the same voltage, the way an op-amp lab is powered.

Pins

Pin	What it does
V+	Held voltage above V-.
V-	The other terminal. Nothing connects it to ground but a wire.

Properties

voltage is -1000 to 1000 V, 5 V by default.

While it runs

The readout is V+ above V-.

What the model gets right

It holds its voltage. 9 V into a 1 k and 2 k divider puts 6 V across the 2 k, as the exercise says.

What it does not model

An ideal source would make some circuits impossible to solve: two of them in parallel at different voltages, or one with a wire across it. So the source is its voltage behind 1 milliohm, which no exercise's numbers notice, and those circuits become a very large current instead. There is no current limit: for one, use the bench power supply.

Common mistakes

Expecting V- to be ground. Wire it to a ground symbol, or to the circuit's ground, when that is what you mean.

For an AC source, use the signal generator: a sine wave of the amplitude you want, with the offset at 0 V.