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Narrow-band filter circuit with the adjustable Q value and f

2017-02-21 20:54  
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Narrow-band filter circuit with the adjustable Q value and frequency
The narrow-band filter circuit with the adjustable Q value and frequency is as shown in the figure. This circuit is an active narrowband filter with adjustable Q value and frequency. It uses the Venturi bridge positive feedback, the loop gain is lower than 1. The feature of this circuit is if you adjust the Q value, you will not influence the center frequency. Because the Q value only has relationship with the gain of the return circuit. When the gain is 600, the Q value is 2000; when the gain is 140, the Q value is 30. In general venturi bridge oscillators, for the in-phase input ports, the amplifier gain must be more than 3 to start oscillation, the amplifier gain is less than 3 in this circuit.