The electrical circuit of the power supply of the laser diode is shown in the picture:
Diode laser has three pins and consists of (a diode that emits a laser beam), and control the photodiode, which is designed to control power output. Anode and cathode of the diode laser is connected to the control pin and also connected with the case.
The tracking scheme with a feedback current produces a forward bias diode laser. The stabilizer is automatically adjusted return current supervisory diode, in order to maintain the installed capacity of radiation. Adjusting the current is an operational amplifier OP, in the inverse input is fed a reference voltage of 2.5 V with a resistor R1, R2.
The potential for direct input 3 varies with the inverse photodiode current of the laser diode. Indeed, the photodiode current passes through resistors R4 and Aj, is converted into a voltage. The output voltage of OP depends on the photodiode reverse current, as well as the trimmer Aj, which is determined by the light beam power. The lower the voltage output of the OP, the more current flows into the diode, consequently, the brightness of the beam.