Electromotor constant speed control circuit composed of the

The Electromotor constant speed control circuit composed of the CA0358 is as shown in the figure. In the circuit, the differential amplifier A2 detects the ends voltage Um of the electromotor, A2 adds the output voltage Um to the inverting input port of the differential amplifier A3. At the same time, the A1 detects the ends voltage of Rm/10 (Rm is the DC resistance of the electromotor armature) UR, and it amplifies the voltage to 10 times. The voltage adds to the in-phase input port of A3. RP4 can be used to adjust the magnification of A1. You need to make the electromotor break away from the power circuit and make it stop working, you can adjust the RP4 until the A3's output is zero.