Circuit Description

The circuit diagram 40V 2A power supply circuit has been described here. The central part of this circuit is the voltage regulator IC LM 317. This power supply circuit is ideal for circuits such as power amplifier circuit can deliver a current of 2A. In this circuit the transistor Q1 acts as pass transistor for increasing current capability. The output voltage is set to 40V by using resistors R5 and R8.

Parts List

Resistors: R1 (39 ohm 1 or 2W Resistor), R2 (22 ohm 1/4W Resistor), R3 (68K 1/4W Resistor), R4 (220R 1/4W Resistor), R5 (47K 1/2W Resistor).

Capacitors: C1 (3300µF 50V Electrolytic Capacitor), C2, C5 (100nF 63V Polyester Capacitors), C3 (10µF 63V Electrolytic Capacitor), C4 (220µF 50V Electrolytic Capacitor).

Active Components: D1 (Diode bridge 4A), D2 (1N4002 Diode), D3 (LED any color), U1 (LM317), Q1 (TIP42A Transistor), T1 (230V Primary, 40V 2A, Secondary, mains transformer).

Circuit Diagram

Power Supply Circuit Using LM 317 IC

Power Supply Circuit Using LM 317 IC


  • Use a good quality PCB to assemble this circuit.
  • Use four 1N 4007 Diodes if Diode Bridge is not available.
  • If you want any other out put voltage use a 10 K pot instead of R5 and adjust it.