Designer’s Guide Community

‹ Previous topic | Next topic ›

Pages: 1

oscillation amplitude depends on initial condition? (Read 2222 times)

vikram1977

New Member

Offline

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

IP Logged

raja.cedt Senior Fellow Offline 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.
Back to top	IP Logged

buddypoor Community Fellow Offline 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.
Back to top	LvW (buddypoor: In memory of the great late Buddy Rich) IP Logged

loose-electron

Senior Fellow

Offline

Best Design Tool =
Capable Designers

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

Jerry Twomey
www.effectiveelectrons.com
Read My Electronic Design Column Here
Contract IC-PCB-System Design - Analog, Mixed Signal, RF & Medical

IP Logged

Pages: 1

‹ Previous topic | Next topic ›