| 摘要 |
PURPOSE:To obtain an accurate output regardless of the polarity and symmetricalness by using the output of a comparator circuit which compares in level the difference signal between the positive and negative peak holding circuits with the signal of another positive peak holding circuit having a large time constant as a signal detection output. CONSTITUTION:With application of a vertically asymmetical input HF signal waveform, the negative side is substantially clamped by an earth through a clamping circuit 1 of an input stage. Therefore both V5 and V6 are set at an earth level respectively. Thus the output V7 of a differential amplifier is equal to the output V2 of a positive peak holding circuit 2. In case the input HF signal waveform is vertically symmetric, the output V5 of a negative peak holding circuit 5 and the output V6 of a clamping circuit 6 have approximately same waveform. The outputs V2 and V6 are supplied to a differential amplifier 7 and turned into a signal corresponding to the difference of both signals to obtain a waveform of the V7. In such a way, the big variance of amplitude is produced, and some part has a drop lower than a comparison level V4. Thus, an accurate HF signal detection output is obtained. Then it is possible to obtain the accurate information on the relative positional relation between a pickup and a recording track.
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