| 摘要 |
PURPOSE:To enable to control the speed of a miniature DC motor even if the motor has low counterelectromotive voltage by comparing the voltage generated at a resistor connected to a constant current circuit with the counterelectromotive voltage and controlling the speed of the motor. CONSTITUTION:An operational amplifier 19 outputs a signal responsive to the deviation between a reference voltage divided from the voltage of a reference voltage source 21 and the voltage of a resistor R10 due to the emitter current of a transistor Tr5, thereby maintaining the collector current of the transistor Tr5 constant. An operational amplifier 18 inputs as a reference voltage the voltage drop of a resistor R13 due to the collector current of a transistor Tr5, amplifies the deviation between the counterelectromotive voltage of a DC motor 16 supplied with the refernce voltage from the terminal 13 and the voltage drop of the internal resistance of the motor, and drives transistors Tr3, Tr4, thereby controlling a current flowing through the motor 16. |
