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Message started by fern on May 31st, 2006, 9:33am

Title: Running differential LNA simulation
Post by fern on May 31st, 2006, 9:33am
Hi All,

I'm designing a differential LNA, how do i simulate it in cadence using just 2 ports?

From analogLib, i realised there are 2 components balun and a phase splitter. What is the difference and which component should i use.


P.S. I know that there was a eariler mail regarding this question, but i did not quite understand the solution.

Thank you.

Best Regards
Fern

Title: Re: Running differential LNA simulation
Post by ACWWong on May 31st, 2006, 10:29am
Try looking at

http://www.designers-guide.org/Analysis/diff.pdf

for general differential circuit simulation guidance.

you can use 1 port for the input differential, and a 2nd port as the differential load. But there is no real constraint as to the number of ports allowed when simulation is cadence (sp, or spectreRF), so long as you number and include them correctly in the simulation you can also use ports to the common-mode generation.

hope it helps.

Title: Re: Running differential LNA simulation
Post by mikki33 on Jun 1st, 2006, 1:38am
You may use VCVS (voltage controled voltage source, gain=-1) to split the single ended input signal into the differential one. The same is useful at the output to combine diff. signal into the single ended.

Title: Re: Running differential LNA simulation
Post by ACWWong on Jun 1st, 2006, 8:20am

mikki33 wrote on Jun 1st, 2006, 1:38am:
You may use VCVS (voltage controled voltage source, gain=-1) to split the single ended input signal into the differential one. The same is useful at the output to combine diff. signal into the single ended.


VCVS has zero source impedance, so although you can do this in the LNA design you must account for finite source and load impedances (both differential & CM).... ie you nedd to add them in to insure loading/matching effects are included. This is why the port/balun method is better.

Title: Re: Running differential LNA simulation
Post by fern on Jun 4th, 2006, 9:15pm
Hi All,

Thanks for the help, it was very helpful..
I'm most grateful...

Regards
Fern

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