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Design >> Analog Design >> ring vco
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Message started by vijay on Nov 14^th, 2005, 5:26am

Title: ring vco
Post by vijay on Nov 14^th, 2005, 5:26am

Hi,
I have a symmetric load 4 stage ring vco for simulation.Initially I try to simulate it by giving constant bias volatages at the PMOS bias and NMOS bias voltages. I do a transient analysis for observing the oscillation.But instead the simulation shows the two voltages stuck up at high (3.814V and 3.125V) for a 0.6um process.
pmos bias volatge is 0.5V and NMOS as 2.5V.
Thanks in advance,
V

Title: Re: ring vco
Post by Sezi on Nov 23^rd, 2005, 10:02am

The differential voltages, both of them stuck at high? Check your circuit maybe you have made some wrong connections..

Title: Re: ring vco
Post by ywguo on Nov 23^rd, 2005, 6:26pm

Hi, Vijay,

I think that stuck is due to wrong bias. Do you bias the PMOS and NMOS using voltage source?

Please bias your ring VCO using a reference current, and generate the bias voltage for ring VCO using current mirror. :)

Best regards,
Yawei