# Filter

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#### viki da viper

##### New Member
Hi Guyz,

I have a small question. I am a first year student doing Electronic and Electrical eng. We have still not done filters in our case, we get to do them in our third year. In the mean time I am reading about filters and stuff I have a question about the Notch filter diagram attached;

1. Is the cut-off frequency 1/2piRC ?

2. How can you find the gain of the notch filter ? like what is the formula?

I am completely new to this topic. So I would really like you people to help me out. Thx

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#### ericgibbs

##### Well-Known Member
Hi Guyz,

I have a small question. I am a first year student doing Electronic and Electrical eng. We have still not done filters in our case, we get to do them in our third year. In the mean time I am reading about filters and stuff I have a question about the Notch filter diagram attached;

1. Is the cut-off frequency 1/2piRC ?

2. How can you find the gain of the notch filter ? like what is the formula?

I am completely new to this topic. So I would really like you people to help me out. Thx
hi,
Get this application sheet from Texas Inst
Section 16 will be useful for your course.

http://www.electro-tech-online.com/custompdfs/2009/04/slod006b.pdf

#### ericgibbs

##### Well-Known Member
hi,
This is a rough simulation for your circuit using LTSpice.

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#### confounded

##### New Member
Hi, i believe your notch filter works by adding 2 signals that have been shifted 180 degrees out of phase at the cut off frequency.

cut off frequency = 1/2piRC as you thought.

I do not know how to calculate gain, would be interested to know if you find out.

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