| 摘要 |
PURPOSE:To simplify the structure of a reproducing signal processing system and to reduce the cost by changing over the passive element composing an active blow pass filter according to the level of DC voltage impressed on a control input terminal. CONSTITUTION:The active blow pass filter 12 connected to a demodulator 2 is composed of plural passive elements, e.g., a 1st resistance body 13 and 1st and 2nd variable capacity diodes 14, 15. In this case, the variable capacity diodes 14, 15 in one active blow pass filter 12 are selected with the level of DC voltage impressed on a control input terminal 11 to correspond with the band-limit mode of FM modulation frequency. The need for using a low pass filter on each mode of the respective band limitation is thus eliminated, the circuit structure is simplified and becomes inexpensive.
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