Formula source
Ideal voltage source set by a formula (SPICE B): V(out+ − out−) = 2*a. a and b are the voltages on the two inputs, measured from out −; t is time in seconds. Inputs draw no current; an input left unconnected counts as 0 V. An element for modelling, not a part you can buy.

Try it on the benchThe lab drops it on an empty bench and opens its datasheet card.
Pins
- input a (measured from out −)
- input b (measured from out −)
- out +
- out −