| 摘要 |
A resistor (R) is connected between a power source (Vcc) and an input terminal (1) of a motor speed controlling circuit (200'), and a motor of internal resistance (Ra) is connected between an output terminal (2) and the power source (Vcc). In the circuit (200'), a constant current source (8) and a reference voltage generator circuit (9) are connected to the input terminal (1), so that the output voltage of the generator circuit (9) is applied to a reference terminal (a) of an error amplifier (10) and the output voltage of the output terminal (2) is applied through a resistor (R<u11>u) to a comparator terminal (B). This circuit (200') controls so as to provide the relationship, represented by a formula //cV = I<u3>u(R<u11>u + Ra), between the difference voltage //cV cross the terminals (a) and (b) of the amplifier (10) and the current I<u3>u flowing through the resistor (R<u11>u). Thus, the motor speed is maintained constant with respect to not only the load but power voltage variations by controlling the current of the output terminal of the circuit (200'), that is, the motor current by means of the output of the amplifier (10). |
