A new constant-Q CMOS active inductor with applications to low-noise oscillators

This paper investigates the dependence of the quality factor of CMOS active inductors on the signal swing of the inductors and its impact on the phase noise of LC-tank oscillators employing the active inductors. A new CMOS active inductor with a nearly constant quality factor is proposed. Two 4-GHz LC oscillators with and without constant-Q active inductors have been implemented in UMC-0.13 μm 1.2 V CMOS technology and analyzed using SpectreRF from Cadence with BSIM3V3 device models. Simulation results demonstrate the phase noise of the oscillator with the constant-Q active inductor is -118dBc/Hz at 1 MHz frequency offset.