Frequency variations in one amplifier stage to other AMPstag - RF Cafe Forums

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vu2vic
 Post subject: Frequency variations in one amplifier stage to other AMPstag
Posted: Sun Feb 11, 2007 12:10 pm 
 
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Joined: Sat Feb 10, 2007 10:08 am
Posts: 1
Location: Banglore
I have designed an oscillator using 2n2222A which is generating stable oscillations at 100MHZ . Then later I designed a amplifer stage for this oscillator by using 2n2222A. but the output of this amplifer stage I am getting a frequency change of 4 MHZ that is 96MHZ...I am not able to understand why this is happening and why there is a change in frequency at the output of the amplifer stage.

To solve this problem I started looking at different issues like Impedance matching. I designed impedance matching which improved the output power of the amplifer but the frequency variations are still inchanged.

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wb9jtk
 Post subject:
Posted: Mon Feb 12, 2007 9:07 pm 
 
General
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Joined: Tue Dec 26, 2006 5:39 pm
Posts: 58
I assume it is a L-C oscillator, not crystal-controlled.

There are many possible explanations for this.

Insufficient buffering between the oscillator circuit and the amplifier circuit.

Feedback from amplifier (need better shielding, power supply decoupling, etc.)

Power supply regulation (if you have varactors or other voltage dependant capacitances in our L-C) changes with addition of amplifier

If you post the circuit here on the forum, you will probably get more suggestions.




Posted  11/12/2012