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https://designers-guide.org/forum/YaBB.pl Design >> Analog Design >> oscillation amplitude depends on initial condition? https://designers-guide.org/forum/YaBB.pl?num=1323339879 Message started by vikram1977 on Dec 8th, 2011, 2:24am |
Title: oscillation amplitude depends on initial condition? Post by vikram1977 on Dec 8th, 2011, 2:24am hello everybody i am simulating a vco , to build up the oscillation i set an initial condition on a given node my probleme is that according to the initial condition i pick, tha amplitude of oscillations change. it dosn't make any sense for me can you help me please is that a problem with my circuit or with the simulator ps: i use spectreRF regards |
Title: Re: oscillation amplitude depends on initial condition? Post by raja.cedt on Dec 8th, 2011, 3:43am hello, i am sure some thing is wrong, becaz VCO is a non-linear system hence independent of initial conditions, may be starting dynamics are depends some time. Please provide some more info to resolve. Thanks, Raj. |
Title: Re: oscillation amplitude depends on initial condition? Post by buddypoor on Dec 8th, 2011, 5:08am Hi Vikram, the most secure and the most realistic method is not to use an initial condition but to switch on one of the power supplies in Tran simulation. |
Title: Re: oscillation amplitude depends on initial condition? Post by loose-electron on Dec 8th, 2011, 7:47am Initial Conditions of a current in the inductor is the best way to get a LC oscillator running. Try it, you will like it! However the oscillator needs to settle out to a final amplitude, and that may take many thousnads of cycles of the oscillator to do so. A trick - use the IC current in L method as described. Then see if amplitude builds or drops in transient simulation. Adjust the current up-down till you get the right amount so its close to the final oscillation amplitude. Speeds up the simualtion process a lot, especially with high Q things like crystal oscillators |
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