Circuit Description

The circuit diagram of Dual adjustable power supply has been given here. This circuit is based on two ICs namely LM 317 and LM 337. Among these ICs, LM 337 is the negative complement of LM317. These ICs work at voltage range between 1.2 V and 30V and are capable of delivering 1.5A current. One of the most advanced features of these ICs is the short circuit protection.

This circuit gives an output dual DC voltage in the range of -15V to +15V. Filtering and ripple rejection in this circuit is accomplished by the series of capacitors from C1 to C8. The job of controlling the output is done by resistors R1, R2, R3 and R4 (R1 and R2 for LM 317 and R3 and R4 for LM 337).

Parts List


C1, C2 (2200 uF 50V)
C3, C4, C5, C7 (2.2 uF 50V)
C6, C8 (100 uF 50V)

R1, R4 (5K Potentiometer)
R2, R3 (220 Ohms 1/4 W Resistor)

Active Components:
D1 to D4 IN 4007 Diodes
U1 LM317 U2 LM337

T1 (24 0 24 Center Tapped 2 Ampere Transformer)
S1 (SPST 2 Ampere Switch)

Circuit Diagram

Dual Adjustable Power Supply Circuit
Dual Adjustable Power Supply Circuit


  • This circuit is a must on an electronic hobbyist’s workbench.
  • The transformer should be produce a min of 3 A with (24 0 24) output voltage.
  • Resistors R1 and R4 can be turned to vary the positive and negative voltages.

Adequate heat sinks should be provided for ICs.