# sizing of the cmos vco

The following indications can be used for the sizing of the oscillator:

• A reduced C leads to a high dependency of the parasitic capacitances;

• For a high C we have a higher current consumption;

• A reduced L leads to a high Gm which implies that a reduced resistance is

necessary to maintain the power dissipation;

• A high L implies a reduced C which means that the tuning frequency

diminishes,

• The power dissipation increases with the increase of the oscillation frequency;

• A Gm*Rp>1 is necessary for the start of the oscillation;

• The output amplitude is determined by the polarization current Vout=I*Rp or by

the entering of the transistors in the triode or cut-off regions, Vout=Vdssat

• To minimize phase noise, the oscillation amplitude should be maximized,

• The phase noise at a determined deviation frequency improves the tank’s Q

and the carrier’s power increases,

• The noise is inversely proportional to the square of the deviation frequency.