| 摘要 |
PURPOSE:To eliminate the variation in the rotational speed of the small DC motor due to variation in the power source voltage, by varying the potential given to each input terminal of an error amplifier circuit in response to the variation in the voltage of a DC power source. CONSTITUTION:One terminal of a tachogenerator 9 is connected to the DC power source Vcc, and the other terminal is connected to one terminal of variable resistor VR to the other terminal of which the DC power source Vcc is connected via a diode D. The input terminal A of a reference voltage source E to the other terminal of which the DC power source Vcc is connected. While the input terminal B of the error amplifier circuit 10 is connected to the variable resistor VR. One terminal of a feedback capacitor is connected to the input terminal B of the error amplifier circuit 10, and the other terminal of said capacitor is connected to the collector of a driving transistor. In this constitution, since the potentials at the input terminals A and B of the error amplifier circuit 10 vary in response to the variation in the voltage of the DC power source Vcc, the rotational speed of the DC motor is kept constant. |
