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Design >> RF Design >> Ring VCO Design
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Message started by jimwest on Dec 17^th, 2007, 10:42pm

Title: Ring VCO Design
Post by jimwest on Dec 17^th, 2007, 10:42pm

Hi Folks,
I'm a noobie in ring vco desgin.
Is there a way to build a ring vco through the given spec like the opamp design?
If the following parameters are given, how can I determine the w/l of the delay stage?
1.frequency range
2.gain
3.swing
4.Jitter/phase noise performance
5.power consumption

Thank you.

Kindest Regards,

Jim

Title: Re: Ring VCO Design
Post by Stefan on Dec 18^th, 2007, 12:44am

The performance of RO's strongly depend on the technology you'll use.

There are a bunch of papers available dealing with the sizing of RO's for optimal phase noise performance (or optimal tunability).
In general :
Start with a minimum-sized circuit, with as few delay stages as possible (3, 4 or 12 would be typical).
You can then do a simple parametric analysis for a comparison of the behaviour for sizing / power consumption / phase noise.
Gain and swing is typically of no issue (gain as high as possible for low phase noise, swing rail to rail - inverter).

Regards,

Stefan

Title: Re: Ring VCO Design
Post by jimwest on Dec 18^th, 2007, 6:06pm

Hi Stefen,
Thank you very much.
But I think your flow can only be used in invertor design, which will also take time to try different w/l and number of stages.
Then how about the Maneatis delay cell or the Lee/Kim's delay cell?
Is there a method for optimizing the w/l of the latch (or diode connection mos) in those kind of cell?

Regards,

Jim