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Parasitic oscillations - 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.

Post subject: Parasitic oscillations Posted: Tue Jul 26, 2005 7:15 am

Could someone suggest a couple of good references on low frequency parasitic oscillations in microwave amplifiers?


Post subject: Posted: Tue Jul 26, 2005 7:58 am

Site Admin

Joined: Mon Jun 27, 2005 2:02 pm
Posts: 373
Location: Germany

Please try the following:

http://www.semiconductors.philips.com/a ... /LNA97.pdf

Good luck!

Best regards,

- IR


Post subject: ThnxPosted: Tue Jul 26, 2005 8:58 am
Thank you very much for the reference. I will have a re-look at the biasing circuitry and the bypass capacitors in my circuit. From a practical standpoint, how would one determine (when testing the amplifier) if low frequency products were modulating the suply voltages?


Post subject: Posted: Tue Jul 26, 2005 9:25 am

If you know the bandwidth of your input modulated signal you can see if the voltage on various points (Base, collector) on the amplifier's circuit has AC components (With high-speed oscilloscope or with spectrum analyzer don't forget to use DC block for this measurement) if you see these components at these points, you can estimate by their magnitude if your bypassing is adequate or not.

Alternatively, you can inject 2 input CW signals with known offset between them and do this measurement.

Should you need more information, please let me know.

Posted  11/12/2012
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