Notch filter using negative resitance

Status
Not open for further replies.

stenzer

Advanced Member level 3
Joined
Oct 1, 2012
Messages
898
Helped
125
Reputation
254
Reaction score
189
Trophy points
1,323
Activity points
9,207
Hi,

I'm trying to realize a "narrow" notch filter which should operate in the lower MHz - range. Therefore I need a large inductance. This results in a low Q.
I read that it is possible to enhance the Q by adding a negative resistance with a transistor.

Can anyone tell my how to design such a filter?

Thanks
 

Yes is possible to do this mechanism to enhance the Q of the resonator. The circuit is basically a feedback amplifier with variable gain.

 

If we take a simple LC tank as a notch filter...

Q is a result of L:C ratio interacting with neighboring impedances.



The available current has a lot to do with determining which LC ratio will be most suitable.
 

Hi,

thank you for your replies. I tried to realize the negative resistance with a current sink, by changing its Drain voltage. Unfortunately it doesn't work well. Is there a better (and simple) way do enhance the Q?

BR
 

Status
Not open for further replies.

Similar threads

Menu
Log in
Register
Cookies are required to use this site. You must accept them to continue using the site. Learn more…