| 摘要 |
PURPOSE:To make the starting torque and the maximum control torque large and to make the fabrication of a semiconductor IC circuit easy, by forming base currents which saturate the transistors constituting the current mirror of a motor current so that said base current can be supplied. CONSTITUTION:When the number of rotation of a motor 9 increases, a reverse electromotive voltage becomes high, the voltage at a terminal 26 is decreasd, the base bias of a Tr30 which forms a differential amplifier becomes low, and the collector current of a Tr34 which forms a current mirror is increased. Therefore, the collector current of a Tr38 is increased, the base current of a Tr is decreased, the collector currents of Tr11-14 forming the current mirror of the motor current are decreased, and the number of rotation is reduced. At this time, since the collector of the Tr40 is connected to a power-supply terminal 27, and the base current which can saturate the Tr11-14 can be supplied, the maximum control torque and the starting torque of the motor can be made large. |
