LA5521 application circuit

Its LA5521 application circuit

The working principle is briefly described as follows: when the power supply voltage vcc changes or the mechanical load of the motor
changes, the motor speed will change. The back electromotive
force E is proportional to the rotational speed. As the marrow changes, the voltage across the motor also changes accordingly .
The voltage v sampled from the two points of the adjustable resistors 1 and 4. These voltage changes are reflected and sent to
the non-inverting input terminal of the error amplifier. It is compared with the reference voltage VREF at the inverting input terminal.
After the error is amplified, the bases of the two transistors are controlled, and the output voltage (pin 3) is adjusted. The output voltage of pin 3
is V. . It has a negative feedback control relationship, and the closed-loop control result tends to maintain a constant speed.