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    Oscillations dying out

    my current starved vco oscillations are dying out after some nanosecond. what could be the possible reasons? and how to rectify it?

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    Re: Oscillations dying out

    Hi,

    Replace C15.

    Joke aside. How do you think we can help when you don't give a single information about your hardware? By guessing?
    --> give complete informations. Like schematics, PCB layout, exact part numbers and manufacturers, scope pictures, test conditions...

    Klaus
    Please don´t contact me via PM, because there is no time to respond to them. No friend requests. Thank you.



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    Re: Oscillations dying out

    "Some nanoseconds" sound like a pure simulation question. Anyway, show a schematic.



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    Re: Oscillations dying out

    maybe "current starved" has something to do with it?

    maybe there is too large a load internally or externally?



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    Re: Oscillations dying out

    Humans also die out when we are starved.



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    Re: Oscillations dying out

    This is a conventional 3 stage current starved vco. Biasing is 620mV, but when i am doing biasing of 630mV oscillation sustain.
    [ATTACH=CONFIG]157437[/ATTACHClick image for larger version. 

Name:	IMG_20200121_171903.jpg 
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ID:	157438]



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    Re: Oscillations dying out

    Quote Originally Posted by MILIND_7 View Post
    This is a conventional 3 stage current starved vco. Biasing is 620mV, but when i am doing biasing of 630mV oscillation sustain.
    does this mean that at bias of 620 mV, it dies out, as in the photo you posted,
    and that at 630 mV the oscillation does not die out?

    if so, looks like you've solved it.



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    Re: Oscillations dying out

    yeah its solved but I want to know how? and one more thing is I simulated for 100ns , how would i get to know that it will still oscillate at 10 us?



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    Re: Oscillations dying out

    1. You can verify by checking the loop gain.
    2. Choose initial conditions that result in a start magnitude below steady state. You'll see a rising magnitude at the start.



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    Re: Oscillations dying out

    Thank you so much for your help.
    as I have designed conventional 3 stage current starved vco, what i can do to increase its tunning range,decrease phase noise ,make it independent of process variations. can you suggest me with some reference it will be a great help.



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