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Design >> Analog Design >> Stability analysis of Automatic Amplitude control loop
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Message started by osc on Oct 6^th, 2009, 8:31am

Title: Stability analysis of Automatic Amplitude control loop
Post by osc on Oct 6^th, 2009, 8:31am

Hi

I am planning to design an oscillator with Analog amplitude control loop. The problem I face is that this loop by nature is very non-linear and difficult to check for stability. Stability problems lead to a phenomenon called squegging.

Can some one help with the simulation/analysis of such a loop.

Thanks :)

Title: Re: Stability analysis of Automatic Amplitude control loop
Post by buddypoor on Oct 7^th, 2009, 12:53am

osc wrote on Oct 6^th, 2009, 8:31am:

There are some remarks to be made to your posting:
1.) There are several different alternatives for amplitude control - and before analyzing such a loop your choice has to be made. Try to become familiar with these options (literature study).
2.) The loop must NOT be "very" non-linear. In contrary, it should be as linear as possible and as non-linear as necessary to do the job.
3.) Squegging is not a stability problem, but the normal behaviour of each control loop - as the result of the error signal which swings around a certain middle value.
4.) Question: Do you have chosen already the type of oscillator circuit?

Title: Re: Stability analysis of Automatic Amplitude control loop
Post by osc on Oct 7^th, 2009, 7:16am

Thanks for your inputs..
I am checking for the literature at present ....
do you have any recommendations..
The problem I can think of with squegging is a very degraded phase noise performance and I an reffering to crystal oscillators(pierce)..

Title: Re: Stability analysis of Automatic Amplitude control loop
Post by buddypoor on Oct 7^th, 2009, 7:23am

osc wrote on Oct 7^th, 2009, 7:16am:

Thanks for your inputs..
I am checking for the literature at present ....
do you have any recommendations..

This really depends on the oscillator circuitry. It makes absolutely no sense to speak of an amplitude control loop without knowing the circuitry to be controlled.

Title: Re: Stability analysis of Automatic Amplitude control loop
Post by osc on Oct 7^th, 2009, 7:39am

I am reffering to crystal oscillator (pierce configuration)..

Title: Re: Stability analysis of Automatic Amplitude control loop
Post by raja.cedt on Oct 7^th, 2009, 7:42am

hi,
as above people explained you should decide oscillator architecture first. All these amplitude control and jitter are storngly depends on type oscilalator. Basically whats your application?

Thanks,
Rajasekhar.