OTA-C Arbitrary-Phase-Shift Oscillators

• Published in: IEEE transactions on instrumentation and measurement 2012-08, Vol.61 (8), p.2305-2319
• Main Authors: Shu-Hui Tu, Yuh-Shyan Hwang, Jiann-Jong Chen, Soliman, A. M., Chun-Ming Chang
• Format: Article
• Language: English
• Subjects: Amplitudes; Analog circuit design; arbitrary-phase-shift sinusoidal oscillators (APSOs); Capacitance; Capacitors; Conductors; Enlargement; Equations; Instrumentation; Mathematical analysis; native amplitude control; operational transconductance amplifiers; Oscillators; phase compensation; Phase transformations; quadrature oscillators (QOs); Quadratures; Quality of service; Transconductance; Transformations
• ISSN: 0018-9456; 1557-9662
• DOI: 10.1109/TIM.2012.2184958

This paper exhibits the generation of an operational transconductance amplifier and capacitor (OTA-C) arbitraryphase-shift sinusoidal oscillator (APSO) for an order n ≥ 3 for various advanced applications. A new nth-order quadrature oscillator (QO) is obtained via the algebraic quadrature manipulations of an oscillatory characteristic equation. Based on a phase shift transformation from a quadrature, an APSO is then generated by superposing OTAs with required +/- transconductance(s) in parallel with some grounded capacitor(s) on the QO. For eliminating nonideal and parasitic effects to improve phase accuracy, phase compensation schemes are proposed. A new native amplitude control exploiting the nonlinearity of all employed OTAs of the APSO is presented as well to lead to rather low THD and a lower variation of THD with respect to amplitude enlargement. A fourth-order APSO is demonstrated and simulated using Hspice with a 0.35-μm process for validation. In addition, its real application to a polyphase rectifier is improved. Finally, an experiment using LM13700s shows favorable potential of APSOs.