Electronic – Theoretical break frequency and bandwidth of notch filter

analysisbandwidthfilter

I'm trying to learn how to calculate the bandwidth and break frequency for the notch filter shown below. I was told that wye-delta and delta-wye transformation would be needed, but don't fully understand where to go.

Notch Filter

Below is some of my work thus far for simplifying the circuit to get the transfer function
note: C1 and C2 represent the frequency transformed impedances of their equivalent capacitors; ie, C1 = 1/(1uF *s)
note 2: T-structures should be labeled \$\Pi\$-structures).

Transforms

Taking the Wye-like Structure and Delta transforming the lower-wye, then combining the C2 impedance with the top impedance of the new delta structure, I was able to achieve the following (intermediate) transfer function:

Transform Function

Best Answer

There is an excellent on-line calculator here which contains all the formulas for a twin T notch filter - your circuit isn't a twin T but you can use the formulas as shown below: -

enter image description here

Firstly R3 can be assumed to be infinite and secondly C2 and C3 can be both assumed to be 200nF thus making 100nF in total.

I reckon your filter is notching at 250Hz (according to the online calculator). Good luck with calculating the bandwidth from the formula.

EDIT Here is a start for you: -

enter image description here

Related Topic