| 摘要 |
PURPOSE:To obtain an equalizer applied to a 4-wire type transmission by duplicating entirely all blocks for variable gain control, switching the capacity and gain of other block while a signal is outputted from one block and switching said block after the transient phenomenon is converged. CONSTITUTION:A pre-filter 1 and a post-filter 10 are constituted respectively by active RC filters. A flat automatic gain control circuit 2 switches the gain. Moreover, low-pass filter circuits 3, 9 are provided, which consist each of switched capacitor (SC) circuits, and a fine adjustment automatic gain control circuit 4, coarse adjustment automatic gain control circuits 5, 6, a sample-and- hold circuit 7, and a 100% cosine roll-off filter 8 are provided. Moreover, an input terminal 11 for cut-off frequency control and terminals 12-15 applying a clock signal to the SC circuit are provided. The circuits 2-6 are duplicated for gain switching, and a block to be switched is switched after spike noise and transient phenomenon are converged.
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