Can stabilty factor be nagative values

[narayani]

I have designed low noise amplifier and simulated stability factor values and am getting the some stability factor values as negatives values for some frequencies.

If it comes negative values for some frequencies is it o.k. does it mean unstable or negative value of stability should not come at all.

Can it stability factor values comes negative value, is it not acceptable or it should not come negative value of stability factor at all.

 

[BigBoss]

If k>1 Unconditionally Stable
If 0<k<1 Conditionally Stable/Unstable
If k<0 Unstable

These are valid single stage amplfiers only.

If k<0 ( may be nagtive ) your amplifier will probably oscillate.

 

[narayani]

If k<0 ( may be nagtive ) your amplifier will probably oscillate.

For my amplifier, some frequencies I am getting negative stability values as I showed in the screen shot of #1 posting. If negative stability values comes means, we can think that amplifier will oscillate in that frequencies. Can you clarify it.

 

[Terminator3]

This might help:
(1) **broken link removed**
(2) https://n5dux.com/ham/files/pdf/Avoiding RF Oscillation.pdf
(3) https://wp.kntu.ac.ir/shamsi/HF-Electronic/Slide6.pdf
You can try forced match (1), also take a look on illustration on page 7 of (1).
(2) is very nice to and some examples in (3) to check yourself. Drawing stability circle in some program (like this one: https://fritz.dellsperger.net/smith.html) helps.

 

[ktx2222]

Can it stability factor values comes negative value, is it not acceptable or it should not come negative value of stability factor at all.

I think K can be negative. Look at the equation which is used to calculate K, negative value of K is possible.