Single ended rail-to-rail CMOS OTA based variable-frequency ring-oscillator

A new current-controlled ring oscillator based on a single-ended rail-to-rail operational transconductance amplifier (OTA) and three simple CMOS inverters is presented in this paper. The tuning frequency of the proposed oscillator is achieved by modifying the OTA DC bias current. Our proposed CMOS oscillator has been simulated under 3.5 V with the 0.8 /spl mu/m BiCMOS technology from AMS. For a DC bias current between 1 /spl mu/A to 200 /spl mu/A, simulation results confirm wide tuning range of 1.2 MHz to 36 MHz. The total circuit area is only 0.05 mm/sup 2/.