Hi, I have a question about active filter.

Yunsik Chung

Hi, i was studying about active low pass filter and i was wondering about cut-off freq of above circuit.

I can understand how to calculate the cut-off frequency of active low pass filter that has no cap in feedback loop.

But in above case, cut-off freq is 1/(2*pi*R2*C).

How to derive this equation in this case mathematically?

Also, this active high pass filter's cut-off freq is 1/2*pi*R1*C.

How to derive this equation?

Thanks,

Yunsik

0 Bala Ravi over 5 years ago

Hi Yunsik,

The cut-off frequency or -3dB frequency is represented as the following equation for RC circuits: f = 1/(2*pi*RC). Please refer to the following link to explore the math behind the derivation: https://electronics.stackexchange.com/questions/352028/derivation-of-cutoff-frequency-and-phase-shift-for-rc-low-pass-filter.

Best Regards,

Bala Ravi