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Optical-recording-and-reproducing-device-with-normalization-of-servo-control-signal-using-switchable-automatic-gain-control-circuitry

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Details

Inventors: Yoshida, Toshifumi; Nabae, Mitsuo; Nishinaka, Yasuo; Moriya, Mitsuro;
Assignee: Matsushita Electric Industrial Co., Ltd. (Kadoma, JP)
Primary Examiner: Stephan; Steven L.
Assistant Examiner: Young; W. R.
Attorney, Agent or Firm: Cushman, Darby & Cushman

The present invention discloses a control circuit. An AGC circuit has an input of an x input signal and a gain control amplifier has an input of a z input signal. A division operation of z/x is made by controlling the gain of the gain control amplifier by a gain control voltage issued from the AGC circuit. A division output signal is obtained from an output terminal of the gain control amplifier, and is usable for compensating focus error, tracking error or the like in an optical recording and reproducing apparatus which makes recording and reproducing by a light of laser light or the like. Also included is a switching circuit that allows offset voltages to be reduced.

DETAILED DESCRIPTION An object of the present invention is to provide a control circuit wherein the number of offset adjustment parts is small, high precision is easily obtained, and it can be manufactured in the same integrated circuit with other circuits.
Another object of the present invention is to provide a stable focus servo circuit using the control circuit and a feed back system for a tracking servo circuit or the like.
The control circuit in accordance with the present invention is characterized by providing an automatic gain control (hereinafter referred to as AGC) circuit in which a focus error signal is inputted to a gain control amplifier to which a light magnitude sum signal is inputted.
The division operation is accomplished by control of the gain control amplifier by the gain control voltage of the AGC circuit, and the division output signal is obtained from the output terminal of the gain control amplifier.
The present invention also includes a automatic gain amplifier that possesses two different differential amplifiers, one used for reproducing and another for recording.
Each amplifier has different gain and dynamic range characteristics.
By switching to the appropriate differential amplifiers, a division signal that is appropriate for recording and reproducing modes is obtained.

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