Kabushiki Kaisha Toshiba

Ryuichi Yamashita

Hiroyuki Haga

Shinobu Murai

A tracking error balance adjustment circuit, and a current control circuit used for a variable gain RF amplifier automatically controlled to output a signal having a predetermined amplitude. The tracking error balance adjustment circuit comprises two separate gain adjusting circuits, each having variable attenuation circuit having first gm amplifier of variable gm type, a second gm amplifier of variable gm type connected to the variable attenuation circuit, and an output circuit connected to the second gm amplifier, comprising an operational amplifier circuit having feedback resistor, wherein the first and second gm amplifiers are differentially controlled commonly by a control current. The a current control circuit is arranged in a variable gain RF amplifier connected to a head amplifier circuit amplifying an output signal from optical pickup, controlling a current output of the variable gain RF amplifier so that it changes in accordance with different functions in the range where the control voltage input is lower than the reference potential and the range where the control voltage input is higher than the reference potential, with the result that the gain control sensitivity can be set almost equal between the two ranges.

Tracking error balance adjustment circuit and a current control circuit used for an optical disk playback apparatus, and an optical disk playback apparatus including the same

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Kamakura, Japan

Ryuichi Yamashita