The second-order filter circuit has two structures: Sallen-key and multiple feedback (KFB)
A = 1+R4/R3
The basic circuit of the MFB filter is shown in the figure below. The circuit has two negative feedback branches, and the operational amplifier acts as an infinite gain device to feed the feedback path, and the operational amplifier is used as an infinite gainer, so it is called infinite gain multi-feedback circuit.
A = -R2/R1
High Pass Filter: Replace the low-pass filter resistor with a capacitor, and replace the filter capacitor with a resistor to generate a high-pass filter.
A = 1+R4/R3
A = -C2/C1
There are basically four types of active filters. They are Butterworth, Bessel, Chebyshev and elliptical filters.
Usb Fan,Mini Usb Fan,Usb Rechargeable Fan,Portable Usb Fan
Foshan Shunde Josintech Electrical Appliance Technology Co.,Ltd , https://www.josintech.com