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    Kirt Blattenberger,


RF Cafe began life in 1996 as "RF Tools" in an AOL screen name web space totaling 2 MB. Its primary purpose was to provide me with ready access to commonly needed formulas and reference material while performing my work as an RF system and circuit design engineer. The World Wide Web (Internet) was largely an unknown entity at the time and bandwidth was a scarce commodity. Dial-up modems blazed along at 14.4 kbps while tying up your telephone line, and a nice lady's voice announced "You've Got Mail" when a new message arrived...

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Parasitic oscillations - RF Cafe Forums

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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: ... /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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