Patent ID: 7277378
Filing Date: 2007-10-02
Classification: G11B

Abstract:
1. An offset adjusting circuit for an optical disc comprising: a plurality of offset-adjustment differential operational amplifiers, each of the amplifiers having an input terminal to which an output signal of an optical pickup is input and another input terminal to which a control voltage is applied; an adding circuit that adds output signals of the offset-adjustment differential operational amplifiers to output an RF signal; a direct current component output circuit that outputs a direct current component of the RF signal; an A/D converter that outputs a digital signal of the direct current component; a logic circuit that outputs a digital signal for setting the control voltage, such that a level of the direct current component becomes equal to a target voltage, based on the digital signal of the direct current component; and a D/A converter that outputs the control voltage from the digital signal for setting the control voltage.