stages in a current straved VCO

[vijay_nag]

current starved vco

hi all!

can anybody tell me why should be the minimum number of stages in a current starved VCO be 5? please suggest me any documents regarding this.

regards,
vijay

 

[jonnoi2006]

Re: current starved vco

Current starved can be implement by odd number of stages and at least 3 stages. Because the output signal of final stages feed back to input of first stages must be 180 degree.

 

[dick_freebird]

More stages means more gain. A 3-stage oscillator can hang
up at midrail or fail to start. 5 is your next step up. More is
even better provided you can get to max frequency, you can
run sharper edges but more of them and end up with less
jitter. Use an odd, prime number to avoid multimode problems
(e.g. 9 could oscillate at 9X or 3X unit-delay period).