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oscillation amplitude depends on initial condition? (Read 2224 times)
vikram1977
New Member
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Posts: 1
oscillation amplitude depends on initial condition?
Dec 08
th
, 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
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raja.cedt
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Posts: 1516
Germany
Re: oscillation amplitude depends on initial condition?
Reply #1 -
Dec 8
th
, 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.
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buddypoor
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Posts: 529
Bremen, Germany
Re: oscillation amplitude depends on initial condition?
Reply #2 -
Dec 8
th
, 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.
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LvW (buddypoor: In memory of the great late Buddy Rich)
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loose-electron
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Posts: 1638
San Diego California
Re: oscillation amplitude depends on initial condition?
Reply #3 -
Dec 8
th
, 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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Jerry Twomey
www.effectiveelectrons.com
Read My Electronic Design Column Here
Contract IC-PCB-System Design - Analog, Mixed Signal, RF & Medical
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