Patent ID: 7564207

Claim:
A peak hold circuit receiving at an input terminal a motor-drive-current detection voltage indicating drive current of a motor, shifting the motor-drive-current detection voltage by a given voltage, holding a peak voltage of the shifted voltage, and outputting the peak voltage from an output terminal, said peak hold circuit comprising: a level shift circuit shifting the motor-drive-current detection voltage by the given voltage; a differential amplifier circuit amplifying a difference between an output voltage of the level shift circuit and a voltage at said output terminal to output the amplified difference; and a peak hold control circuit holding a peak voltage of the output voltage of the level shift circuit, said peak hold control circuit including an output transistor outputting from its emitter charging current according to an output voltage of the differential amplifier circuit that is input to its base, a capacitor charged by the charging current to hold the voltage at the output terminal, a bias element generating a voltage substantially equal to the given voltage by which the voltage is shifted by the level shift circuit, and a resistance element provided between the bias element and the output terminal for controlling discharging current of the capacitor.