An RF CMOS differential negative resistance for Q-enhancement

This paper presents a differential Q-enhancement circuit implemented in a standard 5 metal layer, 0.25 μm CMOS process. A differential conductance of -2.8 mS is obtained at 2 GHz. This allows the circuit to compensate for a resistance of approximately 360 Ω. The differential reactance at this frequency is equivalent to 1 pF. An analytical expression for the differential admittance is derived and compared with measurements and simulations. When no power is applied to the circuit, the simulations and estimates match the measured data well. However when supply and biasing are applied, the estimates become optimistic while the simulations and measurements still make a good match.