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    Impact of parasitic capacitance and parastic inductance on DC and crystal oscillator

    we know that we need to avoid parasitic capacitance (electric field) and parasitic inductance (magnetic field) on the RF/Microwave circuit layout. My question is, how about the DC layout and the low frequency crystal layout? we often ignore the parastic capacitance and parasitic inductance on DC and crystal oscillator layout. is it ok?

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    Re: Impact of parasitic capacitance and parastic inductance on DC and crystal oscilla

    Hi,

    With DC ... neither capacitance nor inductance has an effect.

    But then you talk about oscillator ... which can not be DC.

    So are you talking about the DC power supply signals of an oscillator circuit or the (AC) oscillating signals?

    Klaus
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    Re: Impact of parasitic capacitance and parastic inductance on DC and crystal oscilla

    yes, DC power supply of an AC circuit such as PA, LNA Osc and etc.



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    Re: Impact of parasitic capacitance and parastic inductance on DC and crystal oscilla

    Hi,

    A capacitor at the DC power supply is a benefit in either case.
    It stabilizes the supply voltage while it has no negative influence on EMI/EMC ...
    It rather improves EMI/EMC.

    Klaus
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    Re: Impact of parasitic capacitance and parastic inductance on DC and crystal oscilla

    Dear KlausST, refer back to my earlier question, do we need to reduce parasitic capacitance and inductance on the DC supply line of the PA, LNA and Osc ? the DC supply lines are placed closed to RF in this case..



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    Re: Impact of parasitic capacitance and parastic inductance on DC and crystal oscilla

    Quote Originally Posted by pragash View Post
    Dear KlausST, refer back to my earlier question, do we need to reduce parasitic capacitance and inductance on the DC supply line of the PA, LNA and Osc ? the DC supply lines are placed closed to RF in this case..
    If DC tracks are close to RF-especially High Power Level RF-lines, you have to protect DC supply line from RF perturbation.Otherwise RF signals can disturb the oscillator.
    But avoiding the circuit from this perturbation is quite difficult due to limited space for decoupling capacitor/choke inductor. Best way is to move it as much as possible from RF or dirty circuits.


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