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Negative Resistance - RF Cafe Forums

Because of the high maintenance needed to monitor and filter spammers from the RF Cafe Forums, I decided that it would be best to just archive the pages to make all the good information posted in the past available for review. It is unfortunate that the scumbags of the world ruin an otherwise useful venue for people wanting to exchanged useful ideas and views. It seems that the more formal social media like Facebook pretty much dominate this kind of venue anymore anyway, so if you would like to post something on RF Cafe's Facebook page, please do.

Below are all of the forum threads, including all the responses to the original posts.


Quasar
Post subject: Negative Resistance Posted: Sun Sep 16, 2007 9:23 am

Captain

Joined: Fri Aug 11, 2006 6:07 am
Posts: 5
I'm trying to synthesize a negative resistance to add to a circuit. As far as I know there are three popular ways of doing so:
1. Using a device with negative resistance characteristics (e.g. Tunnel Diode).
2. Using a configuration of OpAmps with feedback that gives a negative resistance when seen from the input.
3. Using a configuration of BJTs, ot FETs.

It is the third method that I'm interested in since I'm working at a somewhat high frequency and I need to be able to integrate the resulting circuit on an IC. I'm specifically interested in making a negative resistance using MOSFETs. I did read a couple of papers that talked about the subject but it was quite general, with no reference to biasing or methods of tuning. While I was able to sucessfully simulate a negative resistance using two MOSFETs, the resulting resistance was quite large (tens of Mega Ohms) and it was unstable when put in a larger circuit.

The resistance I need is S-type, in the range of tens of Ohms. Can anyone point me to where I can get more info on this subject?








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