Abstract
This paper presents a new programmable universal filter and quadrature oscillator based on single output operational transconductance amplifiers (OTAs). The proposed universal filter and quadrature oscillator can be achieved into single topology by programming using analog switches. When the circuit programs as a universal filter, it can realize low-pass, high-pass, band-pass, band-stop and all-pass filters with orthogonal and electronic controls of the natural frequency and the quality factor. When the circuit programs as a quadrature oscillator, it provides three-phase quadrature output signals which the condition of oscillation and the frequency of oscillation can be controlled orthogonally and electronically. The proposed structure can be realized based on single output OTAs which is easily implemented both commercially available integrated circuits as OTAs and complementary metal-oxide semiconductor and bipolar junction transistor OTA as IC forms. The performance of the proposed circuit is investigated by SPICE simulation using standard 0.18 μm CMOS process and experiment test using LM13600 discrete component integrated circuit as OTAs is used to confirm the workability of the new circuit.
Highlights
The operational transconductance amplifiers (OTAs) are commonly used to realize analog signal processing circuits [1], [2]
Numerous outputs can be obtained by connecting the input terminals in paralled using discrete component integrated circuits (ICs), the number of devices utilized will equal the number of required outputs, incresing the component count and power consumption
Futhermore, several of these topologies suffer from some drawbacks such as exciting the input signal through capacitors [40], [41], requiring componentmatching condition for obtaining all-pass filtering responses [42], [45], [47], [48], requiring minus-type input signal or double input signal for obtaining some filtering responses [43], lacking orthogonal control of the natural frequency and the quality factor [44] and obtaining the current output that flowing through capacitor which is not ideal for integrated circuits implementation [49]
Summary
The operational transconductance amplifiers (OTAs) are commonly used to realize analog signal processing circuits [1], [2]. The universal filter and quadrature oscillator can be obtained with the same topology [40]-[49] it is necessary to change the connection for obtaining either a universal filter or a quadrature oscillator Futhermore, several of these topologies suffer from some drawbacks such as exciting the input signal through capacitors [40], [41], requiring componentmatching condition for obtaining all-pass filtering responses [42], [45], [47], [48], requiring minus-type input signal or double input signal for obtaining some filtering responses [43], lacking orthogonal control of the natural frequency and the quality factor [44] and obtaining the current output that flowing through capacitor which is not ideal for integrated circuits implementation [49]. Compared with the currentmode universal filters in [46], [47], the proposed filter is absent from passive resistors
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