Follow along with the video below to see how to install our site as a web app on your home screen.
Note: This feature may not be available in some browsers.
yescan these existing stability factors help for balanced amplifier?
What is the right approach to verify stability of multistage amplifiers, stage by stage stability factor? or checking output spectrum by sweeping frequency?
See the followings.
The Designer's Guide Community Forum - Stability for cascaded amplifiers
The Designer's Guide Community Forum - SP simulation and negative real Y
The Designer's Guide Community Forum - Common Source LNA stability
The Designer's Guide Community Forum - How to verify Stability of Total Circuits ?
The Designer's Guide Community Forum - question on stability
If it is an LDMOS PA I assume you will be driving it into the non linear region so I'm not sure that playing with small signal s parameters is ever going to give you anything conclusive.
You are more likely to get very low frequency oscillations if you don't have a well controlled bias network or a feedback path that isn't modelled by simple S parameters. eg there could be mutual coupling between inductors or reflections from the output back to the input via the lid of an enclosure. Sometimes with large signals LDMOS will oscillate at a certain drive frequency and certain drive level only. This is due to dynamic changes in the device that can't be modelled using small signal s parameters. Also, it will be more likely to oscillate at colder temperatures.
The best advice I can give wrt an LDMOS PA is to look very carefully at the gate bias components and make sure that the gate bias is held 'stiff' with a low impedance at low (eg audio) frequencies.
Also, put a tracking generator though the PA stage and look for peaking out of band because you can sometimes introduce problems if the PCB and the device aren't grounded as well as you might think they are. This can lead to instability out of band and this is hard to model so you really have to go and look for signs of it.