| 摘要 |
PURPOSE:To obtain a stable output signal and to improve the S/N ratio of the output signal by applying a DC bias voltage to an electrode or information recording medium when an information signal is reproduced. CONSTITUTION:The capacity Cd of a depletion layer is large when no voltage is applied and there is nearly no deletion layer, but small when a voltage is applied and the depletion layer spreads. The resonance frequencies of a circuit when Cd is large are denoted as f1 and f2 and the oscillation frequency f0 of an UHF-band oscillator is so adjusted so as to be on the shoulders of resonance curves of f1 and f2, thereby obtaining the detection output according to variation in the Cd of the depletion layer. Further, the DC bias Vb is applied to the electrode or recording medium. The voltage Vb is set to a voltage which reaches the maximum value Cmax of the electrostatic capacity in the initial state (before recording) in hysteresis characteristics and the minimum value Cmin of the electrostatic capacity after recording voltage application. When the best bias voltage is applied at the time of reproduction, the stable output voltage is obtained and the S/N of the output signal is improved.
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