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What is the result if only increase the SRF of an inductor?

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yorkyong

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If a spiral inductor is improved to have a higher self resonant frequency (SRF), but remaining the inductance and Q factor, What will a circuit, e.g. VCO, benefit from it?

As in my knowledge, the performace of VCO is determined by Q-factor of inductor. The designers optimize the inductor to have the peak Q at the operation frequency. But the improvement is only in SRF, which seems to have no effect on VCO performance.

However the improvement does do some good to the inductor itself and SHOULD have done good to the circuit, which I am not very clear. Can the experts here give me some ideas about that?
 

Mazz

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In my opinion, and I'm not aVCO expert, if the SRF of the inductor, before and after the improvement, is enough higher respect the VCO frequency, you should not see any difference. Maybe the peak Q is higher now, and the VCO can run at higher freq.
The SRF is the effect of parasitic capacitor of the inductor. For frequencies above the SRF the inductor is a cap. If, before the improvement, this parasitic cap is negligible, after the improvement will be negligible as well.
If I'm wright, you can use the improvement in other way: make a second step to increase the Q (for example with larger tracks), this will bring to a smaller SRF (the one you had at the beginning).
I hope it can help.
Mazz
 

egliu

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Re: What is the result if only increase the SRF of an induct

It may be helpful on harmonic suppression
 

khouly

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Re: What is the result if only increase the SRF of an induct

when the SRF increased the parasitic capacitance of the tank circuit will decrease and this is good
coz the total fixed capacitance will be decreased and this make the frequency of oscillator will depend on the Variable capacitnace
and this is good improvment

khouly
 

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