VCO Design Z. Dilli, Mar 2012

VCO Design Adapted from Ryan J. Kier, Low Power PLL Building Blocks, Ph.D. Dissertation, U. of Utah, 2010.

System Design VCO  Source follower (external bias)  Differential Amplifier (external bias)  Inverter chain Simulations show a center frequency of around 1 GHz, instead of 433 MHz as designed in the referenced dissertation –No varactor parasitics considered; bias voltage unknown Around 4.3% tunability with certain assumptions about inductor parasitics Varactor trade-off: Too small reduces tunability range; too large prevents oscillation

VCO-only Outputs C varactor varying from 160 fF (f= GHz) to 450 fF (f= GHz) Tuning range wider at lower bias currents (affects MOSFET capacitance)

VCO-only Outputs I bias changing from 3 mA (by changing V bias from 1 V to 3 V)

Source-follower and Self-biasing Differential Amplifier Two source followers for the differential outputs of the VCO, designed not to load the VCO output with excess capacitance Self-biasing DA increases output swing for the inverter chain operating more reliably Single-ended output taken out of DA

SF and SBDA operation C varactor =160 fF, f= GHz

Inverter Chain Designed to drive a 1.5 pF load This is difficult with a full swing with this CMOS technology (0.6 um minimum width) at > 100s of MHz frequencies

Inverter Chain Output to 0.3 pF Load

Inverter Chain Output to 1.5 pF Load

VCO Layout

Full Chip Layout