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parallel feed back resistor - 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.


Guest
Post subject: parallel feed back resistor Posted: Tue Aug 23, 2005 3:35 am
Hello!
Can any one explain how do we determine the safe value of parallel feed back resistor being used to level the gain and stabilize the device as well. My concern is the heat dissipation due to Rf energy. I am using it for various RF power out puts eg, 5W,10W etc.


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Guest
Post subject: Parallel Feedback ResistorPosted: Tue Aug 23, 2005 7:19 pm
One of the replies you hear a lot on this site is "what are the details of your application". The reason is that there are no totally general formulas or rules for anything - there are always trade-offs that get made differently, depending on the parameters of the situation. Feedback techniques appropriate for LNAs are not necessarily the techniques you'd use for an HPA.

Normally, you don't want to burn up too much power in resistors, regardless of where they are. If it's RF power you're burning up, that's pretty costly stuff!

So the questions are,
1. What frequency range are you talking about?
2. What kind of circuit are you talking about? That's important because if you need to stabilize a circuit, you already have feedback - and you've got to know the nature, amount, and effects of that feedback.
3. Are there any other objectives? Linearity: harmonic distortion, IMD, Third-order intercept, etc. Efficiency?

Good Luck!


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Guest
Post subject: Posted: Wed Aug 24, 2005 3:29 am
1-50-250MHz
2-Single ended, Class A
3-TOI 10dB higher than P1dB
3-P1dB is 5W
4-Biased at 24V,800mA



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