Using this circuit diagram, can be build a simple voltage stabilizer using discrete electronic components.
With components values given in the scheme, the voltage regulator provides an output voltage of 12 volts
Voltage reference used here is D1, a Texas Instruments type IC TL431C.
D1 provides base current for T1 which produces a voltage of 2.5 V on R3. This allows you to calculate the output voltage of the source, Uo, using this relationship:
Uo = 2.5 [1 + (P1 + R2) / R3] [volts]
For other output voltages, the voltage divider must be adapted, just making sure that the P1, R2 and R3 have at least 1 mA. This is necessary for loading caused by the input current is negligible TL431C's . Power transistor is a Darlington type with a minimum current gain of 1000 to the emitter current of 5 A. This means that transistor require a base current of only 5 mA
Buffer capacitor and radiator for T1 is large enough for output currents up to 2 A.
If you need a higher current (up to 5 A), power transistor mounted on a outside heatsink. Also increase the capacitance of 10,000 uF.