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Measurements >> RF Measurements >> LNA Gain Measurement:No Convergence problem
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Message started by ravigupta on Jun 22^nd, 2003, 1:03am

Title: LNA Gain Measurement:No Convergence problem
Post by ravigupta on Jun 22^nd, 2003, 1:03am

Hi ..
I have been trying to plot the voltage gain of the LNA , but I get an error:
"Convergence difficulties resulted in error requirements being unsatisfied"
and so the simulation goes on indefinitely.
From the cadence documentation I found that this might occur if there are multiple periodic stimuli and their stimulus frequencies are not co periodic (and multiple of PSS analysis period).But I just have one voltage source in my circuit.(the circuit is the same as page 289 of "The Design of Cmos RF Integrated circuits"by Thomas Lee").
Can anyone suggest what might be the cause of no convergence ?
Also,a very fundamental question , does the PSS analysis period correspond to the fundamental frequency of the source we use ?
Thanx,
Ravi

Title: Re: LNA Gain Measurement:No Convergence problem
Post by Mighty Mouse on Jun 24^th, 2003, 12:58am

Ravi,
For LNAs the PSS period should be the same as the period of the driving source.

It is hard to determine what is going wrong with your simulation from the description you have given. Does Spectre transient analysis run okay on your circuit?

- MM -

Title: Re: LNA Gain Measurement:No Convergence problem
Post by ravi gupta on Jun 29^th, 2003, 12:24am

thanx mm ,
the problem was solved when i reduced the tolerance in the pss options..
the simulator itself gave options like :check if my model parameters are correct ...
check if reltol etc are too tight ..
it pointed out the nodes where the tolerances were exceeded .
thanx,
ravi