Class B Amplifier Circuit Diagram - A constant current source source can supply a fixed current to a load regardless of input voltage or load change. LM317 / LM350 / LM338 constant current source is one of the simplest design.. A simple explanation of how a transistor works in a circuit, and how to connect transistors to create a number of different circuits. No mathematics and no complex wording. Just a completely different approach you can understand . . . TOPICS: Adjustable Current Power Supply.