| 摘要 |
The invention relates to electronic filter circuits. In order to stabilise the resonant frequency f0 and the selectivity Q of the characteristics of the filters, the bell and counter-bell filter circuit comprises an amplifier 2 with constant output intensity, an amplifier 3 with constant output voltage, a single resonator 6, a switching unit 4, 5 serving to connect selectively one or the other of the two amplifiers to the resonator and two output terminals 8, 9. When using a parallel resonator driven by the amplifier 2 with constant output voltage, output signals processed by the counter-bell filter can be obtained at the first output terminal 8. When a resonator 6 of parallel type is driven by the amplifier 3 with constant output voltage, output signals processed by the bell filter can be obtained through the second output terminal. Applications to the processing of the chrominance sub-carriers in the SECAM television system. <IMAGE>
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