Power supply :
13.8V 25Amp power supply with LM723+2N6776

This is Hight current power supply 13.8V 25A, For Power circuit electronics. use Ic LM723 and transistor : 2N6776 x 4.
Output Current 0-25A, Volt 13.8V (regulator).

Detail intro:

Any bench supply consists of a transformer with a secondary of about 18 volts AC, a rectifier block and a filter capacitor. With no load, the DC voltage across the terminals of the filter are going to be 18 to 30 volts. Under load the voltage will sag due to the impedance of the secondary of the power transformer. If it sags too far, the supply will loose regulation and it will pass 120 Hertz ripple (hum) to whatever you are powering with it. Since the voltage across the filter capacitor can vary wildly as the load changes we need a method of regulating the voltage. The work of regulation is done by the pass transistors (Q2 to Q5). They in turn arecontrolled by the 723 regulator. Lets look at the 723 in a little more detail now. Note that it has its own filter power supply made up from diodes D1-D4 and filter capacitor C2. The 723 has its own internal highly regulated voltage reference supply (pin 6). Internally the 723 compares this reference voltage to the output of the power supply. Voltage adjustment pot RV1 sets the ratio of the reference voltage to the output of the supply. This sets the output voltage.

The output of the 723 is pin 10. This voltage drives the base of Q1. Q1 acts as a simple amplifier to increase the current available to drive the current hungry bases of the pass transistors. As the load increases on our power supply, the voltage from the wiper of RV1 drops as well. When this occurs the 723 increases the voltage from pin 10 driving the pass transistors harder through Q1. The more base current through the pass transistors, the higher the output voltage. Thus we have regulation, the 723 continuously changing its outputvoltage to meet the minute changes in load on the supply. Remember, the 723 does the thinking, the pass transistors do the work!

Read More in source web:
http://www.seits.org/features/pwrsup.htm
Thank you.