What's the LC tank VCO condition to start up?

[jecyhale]

I have two questions:

1, how to make sure that the VCO will start up?
2, Can we design the start up time exactly.

Thanks.

 

[Blackuni]

Re: LC tank VCO start up

Hi,

Whtz the topology?

if its a colpits then condition for start up is
gmc = ω^2*Rs*C1*C2
gm > k * gmc

whr gmc is critical transconductance.
gm is u r ckt ,,
Rs --> losses in u r tank.

thnx