CDCTA and OTA Realizations of a Multi-phase Sinusoidal Oscillator

摘要

A new topology for a current-mode multi-phase sinusoidal oscillator (MSO) is introduced. It is designed using current-differencing cascaded transconductance amplifiers (CDCTAs) and operational transconductance amplifiers (OTA). Both designs realize odd and even numbers of phase oscillators. The MSO is implemented by cascading first-order all-pass filter stages that are designed with CDCTAs or OTAs and show the same transfer function. The MSO includes n grounded resistors and n grounded capacitors to generate n phases. We highlight the advantage of using OTAs because the resulting MSO circuitry is greatly reduced compared to using CDCTAs, while in both designs the high output impedances facilitate easy driving an external load without additional current buffers. The condition of oscillation and the frequency of oscillation are orthogonal and can be adjusted by varying a bias current. Finally, SPICE simulation results using integrated circuit technology of 0.35 mu m show that the designed MSO provides odd/even phase signals that are equally spaced in phase and with equal amplitude.