Voltage-controlled voltage source second-order band-pass filter circuit

A band-pass filter only allows signals within a certain pass-band range to pass through, while signals with frequencies lower than the lower limit of the pass-band and higher than the upper limit of the pass-band
are attenuated or suppressed.
    A typical voltage-controlled voltage source second-order bandpass filter is shown in the figure.
    The advantage of this circuit is that changing the ratio of RF and wind can change the bandwidth without affecting the center frequency.
    The integrated operational amplifier AJ in the picture uses dual operational amplifier vA747.