Design of Ultra Low Power CMOS Oscillators Using Active Inductors

Abstract

The paper considers the design and tuning of oscillators using active inductors with ungrounded capacitor. The oscillator using this type of active inductor allows one to achieve high oscillation frequencies with low power consumption. Tuning of this oscillator using the variation of bias current or transistor sizes may result in moderate and even weak inversion of the transistors constituting the active inductor. In approaching the operation close to the threshold voltage, the transistor transconductance and the gate-source capacitor are reduced. The paper gives the design examples considering these particularities which are usually neglected and provides the recommendations on the limits of tuning currents and transistor geometry variations.