LASER diode driver circuit

LASER = Light Amplification by Stimulated Emission of Radiation and laser diodes are widely used in different domain applications, it gives focused light ray in visible spectrum and laser diodes will perform good in regulated constant current. Depends on application laser chosen at different range nm (nano meter) wavelength and watts.

In this project LASER diode driver circuit is developed with adjustable voltage regulator LM317 to drive red color 650nm 50mW laser diode. This circuit is suitable for constant and continuous glowing of laser diode. We can adjust the intensity of light by this circuit.

Circuit Diagram

Components Required

  1. Bread board
  2. Laser Diode 650nm, 5mW
  3. IC LM317
  4. Capacitor 0.1uF
  5. Capacitor 1.0uF/16V
  6. Variable resistor 10KΩ
  7. Resistor 240Ω
  8. Diode 1N4007
  9. Battery 9V

Construction & Working


Laser diodes are made as PiN semiconductor that is P type semiconductor and N type semiconductor are separated by i intrinsic layer, depends on the intrinsic semiconductor layer material laser diode’s wave length and color varies. The P type layer concentrated with majority holes & minority electrons then N type layer concentrated with majority electrons & minority holes. Some high power laser diodes manufactured with heat sink to avoid thermal run away.

This circuit begins with filter capacitor C1 0.1uF and it is responsible for filtering high frequency ripples in DC supply. Adjustable voltage regulator IC LM317 biased with ground through variable resistor VR1 and variable output terminal of VR1 is connected at the output pin of IC LM317 through R1 resistor. By changing the VR1 Resistor we can adjust the regulator ICs output voltage. The capacitor C2 balance the output voltage given to laser diode and D1 avoids reverse polarity bias to the Laser diode.

When we apply power supply (here 9V battery) Regulated constant voltage and current reaches the laser diode and drives it to give maximum output. Place Laser diode in this circuit with caution to its polarity, wavelength and power.


Basic Laser & Higher class lasers are dangerous to naked eyes and skin do not expose in its path.

One Comment

  1. S January 4, 2019 Reply

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