Here is a power supply design with built-in short circuit protection. The Zener diode on the Diff pair is being used as a reference voltage to determine the output voltage. There is a pass transistor Darlington pair that serves as a voltage regulator from sampling the current at the output to vary the collector to the desired output voltage using feedback. The resistor in the upper right hand corner connected to an emitter controls the output current under short-circuit conditions.
