Fully Tunable All-Pass Filter Using OTA and its Application

This paper proposes a realization of fully tunable all-pass (AP) filter and its application. Three Multiple Outputs Operational Transconductance Amplifiers (MOOTAs) and a grounded capacitor are used for realizing an all-pass filter which is able to tune in both of the frequency response and gain. The frequency response and gain are independently tuned through particular bias current. The advantage of independent tunable gain is of AP filter that can be widely used in many applications as well as the sinusoidal oscillator. A multiphase sinusoidal oscillator (MSO) using loop-back of three cascaded all-pass sections is raised as an application. Three MOOTAs and a grounded capacitor are constructed as current-mode APN. The PSpice simulations results are described in two parts, AP filter and MSO. It shows the magnitude and phase responses can be independently tuned. The MSO current and voltage outputs are equally spaced in phase of 360/n degree. The harmonic distortion of the sinusoidal output is less than 0.64%.