Small- and large-signal RF characterization of fully-depleted accumulation-mode varactors for low-voltage LC-VCO SOI design

Small- and large-signal RF characterization of fully-depleted accumulation-mode varactors for low-voltage LC-VCO SOI design ■

Bertrand Parvais, P. Delatte, H. Matsuhashi, F. Ichikawa, P. Simon, D. Schreurs, D. Flandre, J. P. Raskin

Abstract ■

The evolution of the varactor sensitivity k v between small- and large- signal regimes and its consequences to the voltage-controlled-oscillators (VCO) design were discussed. It was found that when V GS was going towards negative values, the zero-Vt varactor depleted rapidly giving a sharp C-V curve. The fine-tuning curve of a 2.45 GHz LC differential VCO including the characterized varactor was measured as a function of the bias current. Analysis shows that the tuning curve of a low-power 2.45 GHz VCO is in good agreement with predictions made using DF theory.