This 5V voltage regulator circuit is made using the BD242 power transistor and can provide a maximum output voltage of 5 volts of a maximum current of 1A, can be designed using this electronic circuit diagram.
Constant current source T2-D1-D2-R6 provide high gain and adequate noise suppression on the input voltage. T3 and T4 equivalent to a Darlington transistor, controlled by Q1, whose base and emitter terminals are connected to the output voltage.
Diodes D3 -5 - D6 are designed to provide starting voltage of the regulator. Output voltage is determined by D7 and R2/R3. Resistance R2 can be replaced with a 5-k potentiometer , to compensate zener diode tolerance.