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The Value of Q and Frequency Adjustable Narrow-band Filter C

2017-02-26 09:53  
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The Value of Q and Frequency Adjustable Narrow-band Filter Circuit
The Value of Q and Frequency Adjustable Narrow-band Filter Circuit
As shown in the figure is the value of Q and frequency adjustable narrowband filter circuit. This circuit shows an active narrowband filter whose value of Q and frequency are adjustable. Its positive feedback takes the form of Wien-bridge, while its loop gain is less than one. The characteristic of this circuit is that the center frequency will not be influenced by the regulation of the value of Q, because it is only relevant with the loop gain. When the gain is 600,the value of Q is 2000; when the gain is 140, the value of Q is 30. In general, in Wien-bridge oscillators, the amplifier's gain must be greater than 3 to produce oscillation for non-inverting input ends, but the gain of the amplifier in this circuit is less than 3. The resonance frequency of the circuit is: