my active inductors simulation indicated a small Q（0~1), anyone can help?

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in ADS, i tried to optimize and tuning, all resulted to small Q or negative Q. Why?
anyone studied the active inductors before? plz help! thx!
 

Not my thing, but here are a couple of ideas.

One, are you measuring Q in the right way, and is Q
really relevent in a -simulated- inductor that doesn't
actually store energy at all?

Two, is the thing biased right and operating as you want
it to?

Three, there is going to be a rolloff of performance with
frequency that attends the amplifier, and you'd want
to be looking at this; check that your circuit works OK
at a few decades down from frequency-of-interest and
at least that far down from amplifier UGBW.
 
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    orz

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orz said:
in ADS, i tried to optimize and tuning, all resulted to small Q or negative Q. Why?
anyone studied the active inductors before? plz help! thx!
Click to expand...

Since there are more than one way to realize an active inductor it would be wise to show us the circuit and to inform us about the method used to find the Q value.
 
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    FvM

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    orz

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THX!
i am measuring in imag(Zin)/real(Zin) .
i think although i simulated the schematics as paper's, there may be some differences between the process we used(ex. we both used 0.18um, but Cox is different).
so how can i find the Cox(for example) of the NMOS in ADS?

i got a Q about 3. is it ok? or still too small?

Thank you for your help!

- - - Updated - - -



THX!
this is my circuit.
i have tried to tuning and optimize.
Q= imag(Zin1)/real(Zin1)

if i want to calculate the Zin(it's the function of such as Cox and gm), how do i know Cox and gm? If simulate in ADS, i should get these parameter from ADS. right?
 
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this is the circuit i am trying now.(Port 2 is connected to ground. Port 1 you can replace it with a term of 50 Ohm) and q=imag(Zin)/real(Zin) is about 4. how to make it bigger?
 

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