Voltage-Mode Four-Phase Sinusoidal Generator and Its Useful Extensions

This paper introduces a new voltage-mode second-order sinusoidal generator circuit with four active elements and six passive elements, including grounded capacitors. The frequency and condition of oscillation can be independently controlled. The effect of active element’s nonidealities and parasitic effects is also studied; the proposed topology is good in absorbing several parasitic elements involved with the active elements. The circuit is advantageous for generating high frequency signals which is demonstrated for 25？MHz outputs. Several circuit extensions are also given which makes the new proposal useful for real circuit adoption. The proposed theory is validated through simulation results. 1. Introduction Four-phase sine-wave generators with voltage outputs progressively separated by 90° apart find useful applications in communication and instrumentation systems and hence have been well covered in open literature [1–4]. Some of the earlier works based on transconductance- approach [1] offered compact realization with low transistor counts, but limited in frequency when compared to current conveyor based works [2]. Very novel addition to the literature witnessed compact bread-boarding solutions with scope of future integration of new active elements, like DO-CIBA [3]. Meanwhile, traditional approach of employing band-pass filter for quadrature oscillator realization, capable of generating four-phase outputs, continues to attract recent attention [4]. The four-phase voltage-mode circuit of [5] uses five opamps and five passive components, most of which are in floating form. The works as mentioned so far [1–5] falls in the category of second-order networks. Another variety of circuits employed third-order networks to generate quadrature voltage outputs, with a possibility of extension to four phases by additional active elements [6]. The active- network of [6] used current controlled conveyors and three capacitors. Though the circuit in [6] was intended to generate four-phase current outputs, two quadrature voltage outputs were simultaneously available, a fact not mentioned therein. The discussion on quadrature oscillators’ review is worth a voluminous work and can be restricted here, in view of a recent work [3, and cited therein]. In spite of this restriction, there are many works which find mention for their value, without belittling hundreds of other works, not mentioned herein [7–14]. For instance the work in [10] was a first attempt to use DVCC for oscillator application. Another work later [11] presented voltage-mode quadrature oscillator