US Patent 7796659 Pickup head circuits

Pickup head circuits with a protection circuit capable of preventing unexpected large current flowing through a laser diode during power-on interval. A driving transistor is coupled between a laser diode and a first power voltage, an automatic laser power control (ALPC) circuit is coupled between the first power voltage and a second power voltage, controlling the driving transistor to drive the laser diode. A protection circuit is coupled between the power voltage and a control terminal of the driving transistor, forcing a voltage at the control terminal of the driving transistor to follow the first power voltage during a power-on interval.