The Designer's Guide Community Forum

The Designer's Guide Community Forum
https://designers-guide.org/forum/YaBB.pl
Design >> Analog Design >> problem about ring VCO !
https://designers-guide.org/forum/YaBB.pl?num=1223044292

Message started by pllneil on Oct 3^rd, 2008, 7:31am

Title: problem about ring VCO !
Post by pllneil on Oct 3^rd, 2008, 7:31am

Hi.all.
I am designing a ring VCO ( 3 invertors ) with cascode biasing.
I get the work frequency Fo=Ibias/(k*Vpp),k is a constant,Vpp is the output swing.Obviously ,the Fo relates to the Vpp,then I think in this case the amplitude modulation is introduced,which will influence the performance of VCO(such as jitter, noise and so on)/.

So what should be considered when it is realized.

I am confused with it ,

Any reply is highly appreciated. :)

Title: Re: problem about ring VCO !
Post by loose-electron on Oct 9^th, 2008, 12:30pm

You should have no need for cascodes in a ring oscillator. The only thing that gets you is a more ideal current source which is not critical here.

Other than that, a ring VCO is normally buffered and isolated from its outputs, so I am a bit unsue of the issue at hand. You might want to post your circuits so people can better understand.

Alos, for a good article on ring oscillators circuit architecture, see the PLL paper (IEEE JSSC - around 1995 - 2000) by John Maneatis. (Google it)

Jerry