In the All About Circuits book, I'm up the DC Network Analysis sections. It's all straight forward enough for resisters, batteries, and other components with only 1 lead in and 1 out. However I can't figure out how to apply the rules with components not like that.

- Quad op amp. If only one of these is being used, I have 2 leads going in, 1 out, V-, and V+. If several are being used, I have the added complexity that they're sharing the V- and V+

- Transformer with 5 leads

- Transistors with 3 leads

- Logic gate (This one isn't in the kit, but while we're on the subject...)

- Diodes. Here you can't start by assuming either flow direction will work

How does the math work for these?