Kelly,
Your inductor shows a rising impedance vs. frequency only below the self-resonance point. In other words, it acts like an inductor when you are well away from this point. If you start to get closer to self-resonance, then you would atleast need to use a more detailed model which captures the various parasitic caps and resistances.
Based on this, you can see whether or not your inductor is still usable.
Vivek
kelly wrote on Apr 6th, 2011, 10:36pm:Hi,
ususally in a GHz vco design, the inductor is on the order of <500ph with very high Q, and the frequency operation is way below the self resonance of the inductor.
In the case of an on chip low pass LC filter with f3dB ~300MHz, the inductor value is usually >10nH with the self resonance no higher than couple GHz. Does that mean, I can't trust the simulated AC response highers than the inductor self resonant frequency?
I guess my question is
1. What's reason for operating inductor below it's resonance for the high Q inductor (such as in the vco case)
2. Is the reason for #1 applies to the case when you have a big inductor ( low Q) in the range of 10 - 20 nH?
Thanks.
Kelly