Control circuit of an electric motor comprising an output transistor of NPN type

摘要

An automatic speed control circuit for an electric motor is provided with a d.c. amplifier circuit having an output transistor of npn type. The motor is driven by a control signal supplied from the collector of the output transistor to control the motor speed. The collector of the output transistor is connected to one terminal of the electric motor, while another terminal of the motor and the emitter of the output transistor are respectively coupled to the positive and the negative terminals of a d.c. power source. The control signal supplied from the output transistor to the motor is changed in compliance with any variation of the power source. Therefore, the motor speed is independent of any variation of the power source.