| 摘要 |
PURPOSE: A balance gain tuner is provided to correct mismatch generated during an optical pick-up manufacturing process with respect to light-receiving units. CONSTITUTION: A balance gain tuner includes the first and second amplification circuits(12,14), a subtracter(16), and a controller(18). The first amplification circuit amplifies one of signals for detecting tracking error. The second amplification circuit amplifies the other signal for detecting the tracking error with a controllable gain. The subtracter calculates a difference between the output of the first amplifier and the output of the second amplifier. The controller controls the gain of the second amplifier according to the output of the subtracter. The second amplification circuit includes an amplifier(A3), a variable resistor(R7), and a resistor(R8). The inverted input port of the amplifier receives the other signal for detecting the tracking error and non-inverted input port is grounded. The variable resistor varies resistance thereof under the control of the controller in order to control the gain. The resistor is connected between the inverted input port and the output port of the amplifier to determine the gain of the amplifier in cooperation with the variable resistor.
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