Abstract: An amount of a motor drive current is controlled to an appropriate value. Two coils are provided, and a rotor is rotated by the coils by setting different phases for the supplied currents to the two coils. During a phase where one of the coils is in a high-impedance state, an induced voltage generated in the coil is detected. According to the state of the induced voltage, an output control circuit controls the amounts of the motor drive currents supplied to the two coils.

Abstract: A shift register which receives a transmission clock signal, which is shifted according to the transmission clock signal, and which outputs a gate signal a predetermined time after reset; a reset circuit which outputs a reset signal for resetting the shift register when the reset circuit receives an input of a step signal for driving the stepping motor; and a switching element which receives the gate signal of the shift register and which is switched between a blocked state and a conductive state are provided in a driving circuit of a stepping motor.

Abstract: A servo controller for servo-controlling an operative device, the servo controller is provided with an actuator having a motor for actuating the operative device; a sensor for detecting an operational state of the operative device; a comparator for receiving a detected operational state of the operative device from the sensor and comparing the detected operational state with a target operational state to produce a control signal; and a driver provided between the actuator and the comparator for driving the actuator in accordance with the control signal, the driver including a negative impedance circuit with respect to the actuator.