This is a basic design for a series transistor load voltage regulator, designed to maintain an output voltage of approximately 20V.
Vout is taken across the right hand side, and the switch between two different resistors represents the Load on the circuit. There is no line regulation, however with a variation of 5 volts from Vin (DC) the output still maintains 20V plus or minus 0.4V. This can be seen by switching the input to the AC source.
The 800 Ohm Resistor represents a normal Load condition, and the 5 Ohm resistor represents a shorted load. The increase in Load current causes a larger voltage drop across the 10 Ohm resistor, forward biasing the two diodes and creating a new current path to protect the controlling transistor from an overcurrent situation.
I will make another soon with line regulation, and additionally with some load overvoltage regulation using a crowbar circuit. Please let me know what you think. :)
