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Parallel Feed back Resistor - RF Cafe Forums

The original RF Cafe Forums were shut down in late 2012 due to maintenance issues. Original posts:

Amateur Radio | Antennas | Circuits & Components | Systems | Test & Measurement


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



Posted  11/12/2012

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