Electronically controlled multiphase sinusoidal oscillators using current amplifiers

A novel current‐mode multiphase oscillator topology is introduced in this letter. This is realized by employing current amplifiers and only grounded capacitors. Attractive characteristics offered by the new topology are the electronic adjustment of the oscillation frequency, the absence of passive resistors, and the requirement of only grounded capacitors. Comparison with the corresponding already published current follower based structure shows that the proposed topology has better performance in terms of the number of required active elements, the employment of passive resistors, and the ability for electronic adjustment of the oscillation frequency. Copyright © 2008 John Wiley & Sons, Ltd.     

The CCII+ and the ICCII as basic building blocks in low‐pass filter realizations

Three new grounded capacitor current mode low‐pass filters using two inverting second‐generation current conveyor (ICCII) or one double output ICCII are given. The circuits employ the minimum number of passive circuit components, namely two resistors and two capacitors. The circuits are generated from three new voltage mode low‐pass filters realized with the ICCII. A new grounded capacitor CCII+ current mode low‐pass filter is generated from one of the new voltage mode low‐pass filters employing two ICCII?. A new grounded passive component low‐pass filter with independent control on Q and using three ICCII+ is also introduced. Spice simulation results based on using the 0.5 µm CMOS model are included to support the theoretical analysis. Copyright © 2007 John Wiley & Sons, Ltd.     

Realization of tunable RC-active oscillators using grounded capacitors and voltage amplifiers

A systematic procedure is given to generate a set of tunable RC oscillators, each using two finite gain voltage controlled voltage sources, three resistors and two grounded capacitors. These realizations are shown to be minimal with respect to passive and active elements under the constraint that (one end of) all the capacitors remain grounded. The set consists of four oscillators and is shown to be complete, that is, no additional oscillator circuit can be generated under the given assumptions. A simple approach is then introduced for testing the structures for latch up behaviour. This approach also suggests a way of redesigning the oscillator circuits to render them free of latch up problems, if they exist. Experimental results are found to be in good agreement with the theory.     

Current mode filters using two output inverting CCII

Current mode Tow Thomas filter using two‐output inverting second‐generation current conveyor is given, the circuit has low input impedance, employs two grounded capacitors and three grounded resistors and has independent control on Q. A universal current mode filter capable of realizing the five filter functions is also given. Both circuits have low sensitivities to all circuit components. Spice simulation results are included. Copyright © 2007 John Wiley & Sons, Ltd.     

Voltage mode and current mode Tow Thomas bi‐quadratic filters using inverting CCII

A voltage mode Tow Thomas bi‐quadratic filter using the inverting second‐generation current conveyor (ICCII) is given. The filter has high input impedance, employs two grounded capacitors, and has independent control on Q, independent control on the band‐pass and low‐pass response gain. Three alternative current mode filters are generated from the voltage mode circuit. The three circuits have zero input impedance, employ grounded capacitors and have independent control on Q. Two of the circuits have also all resistors grounded and the other uses only ICCII?and has only one floating resistor. Copyright © 2007 John Wiley & Sons, Ltd.     

CMOS digitally programmable quadrature oscillators

CMOS digitally programmable quadrature oscillators based on digitally controlled current followers and voltage followers are proposed. The proposed designs provide the advantage of programmability similar to the operational transconductance amplifier‐based oscillators while offering improved linearity. In mixed analog/digital systems, the digital tuning feature allows direct interfacing with the digital signal processing part. Novel realizations that provide both voltage‐mode and current‐mode quadrature sinusoidal signals are presented. Employing only grounded capacitors the designs achieve independent control of the frequency and condition of oscillation that can be tuned digitally. Experimental results obtained from a 0.35 µm CMOS chip fabricated using standard CMOS process are given. Copyright © 2008 John Wiley & Sons, Ltd.     

Symbolic analysis of (MO)(I)CCI(II)(III)‐based analog circuits

New nullor‐based models are introduced to describe the behavior of the first generation current conveyor (CCI), second generation current conveyor (CCII), third generation current conveyor (CCIII), their inverting equivalents (ICCI(II)(III)), and/or their multiple output topologies (MO(I)CCI(II)(III)). These nullor equivalents include only grounded resistors to improve the formulation of equations in symbolic nodal analysis. In this manner, it is highlighted the usefulness of the proposed models to calculate analytical expressions in MO(I)CCI(II)(III)‐based analog circuits. Copyright © 2009 John Wiley & Sons, Ltd.     

Electronically controlled oscillator with linear frequency adjusting for four‐phase or differential quadrature output signal generation

This paper introduces novel four‐phase oscillator employing two Dual‐Output Controlled Gain Current Follower Buffered Amplifiers (DO‐CG‐CFBAs), single Current Amplifier, three resistors, and two grounded capacitors suitable for differential quadrature signal production (floating outputs). To control the frequency of oscillation (FO) and condition of oscillation (CO), only the current gain adjustment of active elements is used. The circuit was designed by well‐known state variable approach. The oscillator employs three active elements for linear control of FO and to adjust CO and provides low‐impedance voltage outputs. Furthermore, two straightforward ways of automatic amplitude gain control were used and compared. Active elements with very good performance are implemented to fulfill required features. Suitable CMOS implementation of introduced DO‐CG‐CFBA was shown. Important characteristics of the designed oscillator were verified experimentally and by PSpice simulations to confirm theoretical and expected presumptions. Copyright © 2013 John Wiley & Sons, Ltd.     

All‐pass sections with rich cascadability and IC realization suitability

In this paper, two new circuit configurations for realizing voltage‐mode (VM) all‐pass sections (APSs) are presented. The proposed circuits employ only two differential voltage current conveyors (DVCCs) and are cascadable with other VM circuits due to their high‐input and low‐output impedances. The first configuration uses a grounded resistor and a grounded capacitor without requiring matching constraints, whereas the second employs two grounded resistors and a grounded capacitor with a single matching condition. While the first configuration can realize only one all‐pass response, the second can provide inverting and non‐inverting all‐pass responses with selection of appropriate input port. Adding two grounded resistors to the proposed filters, variable gain APSs can also be obtained. As applications, two quadrature oscillators, each of which using one of the proposed all‐pass circuits, one grounded resistor and one grounded capacitor are presented. SPICE simulation results are included to verify the theory. Copyright © 2010 John Wiley & Sons, Ltd.     

Realization of arbitrary current transfer functions based on commercially available CCII + s

In this paper, a new topology for realizing arbitrary n^th‐order current transfer function (TF), consisting of only plus‐type second‐generation current conveyors (CCII+s), is suggested. The proposed TF simulator employs only grounded capacitors and is free from the passive element matching requirements. The developed TF simulator can be constructed directly with commercially available active components such as AD844s. It has low‐input and high‐output impedances, a feature which makes it fully cascadable with other current‐mode topologies. Moreover, the proposed simulator can provide gain at its outputs. Simulation and experimental test results for various filter examples are included to confirm the claimed theory. Copyright © 2012 John Wiley & Sons, Ltd.     

Harmonic oscillators realized using current amplifiers and grounded capacitors

New configurations of harmonic oscillators, realized using current amplifier blocks and only grounded capacitors, are introduced in this article. The proposed configurations are based on a grounded inductor simulator scheme and on a loop constructed from first‐order sections, respectively. Comparison with the already published topologies shows that the new configurations have attractive characteristics concerning their implementation in integrated form. Copyright © 2006 John Wiley & Sons, Ltd.     

Design equations for fractional‐order sinusoidal oscillators: Four practical circuit examples

Four practical sinusoidal oscillators are studied in the general form where fractional‐order energy storage elements are considered. A fractional‐order element is one whose complex impedance is given by Z = a(jω)^±α, where a is a constant and α is not necessarily an integer. As a result, these oscillators are described by sets of fractional‐order differential equations. The integer‐order oscillation condition and oscillation frequency formulae are verified as special cases. Numerical and PSpice simulation results are given. Experimental results are also reported for a selected Wien‐bridge oscillator. Copyright © 2007 John Wiley & Sons, Ltd.     

A CCII‐based wide frequency range square waveform generator

In this paper, we propose a novel current‐mode solution suitable for the square waveform generation. The designed oscillator, which utilizes only two positive second‐generation current conveyors as active blocks, six resistors and a capacitor, is based on a current differentiation, instead of voltage integration, typical of developed solutions both in voltage‐mode and in current‐mode approaches, so avoiding circuit limitations due to the node saturation effects. The proposed circuit has been designed, as an integrated solution at transistor level, in a standard CMOS technology, with low‐voltage (± 1V) and low‐power (430µW) characteristics. Simulation results have confirmed the good circuit behaviour, also for working temperature drifts, showing good linearity in a wide oscillation frequency range, which can be independently adjusted through either capacitive (in the range pF ? µF) or resistive (in the range M Ω–G Ω) external passive components. Waiting for the chip fabrication, preliminary measurements have been performed using a laboratory breadboard employing the CCII with AD844 commercial component and sample capacitors and resistors. The experimental results have shown good agreement with both simulations and theoretical expectations. Copyright © 2011 John Wiley & Sons, Ltd.     

Current‐mode dual‐output ICCII‐based tunable universal biquadratic filter with low‐input and high‐output impedances

A new tunable current‐mode (CM) biquadratic filter with three inputs and three outputs using three dual‐output inverting second‐generation current conveyors, three grounded resistors and two grounded capacitors is proposed. The proposed circuit exhibits low‐input impedance and high‐output impedance which is important for easy cascading in the CM operations. It can realize lowpass, bandpass, highpass, bandreject and allpass biquadratic filtering responses from the same topology. The circuit permits orthogonal controllability of the quality factor Q and resonance angular frequency ω_o, and no component matching conditions or inverting‐type input current signals are imposed. All the passive and active sensitivities are low. Hspice simulation results are based on using TSMC 0.18 µm 1P6M process complementary metal oxide semiconductor technology and supply voltages ±0.9 V to verify the theoretical analysis. Copyright © 2012 John Wiley & Sons, Ltd.     

A mixed‐mode KHN‐biquad using DVCC and grounded passive elements suitable for direct cascading

In this paper a mixed‐mode (input and output signals can be current or voltage) Kerwin–Huelsman–Newcomb (KHN) biquad with low/high input impedance and high/low output impedance depending on the type of the corresponding signal (current/voltage) is presented. The circuit is constructed using three differential voltage current conveyors (DVCCs), two grounded capacitors and three grounded resistors. The circuit simultaneously provides bandpass (BP), highpass (HP) and lowpass (LP) responses when the output is current and notch, BP and LP responses when the output is voltage. The notch and allpass responses can be obtained by connecting appropriate output currents directly without using additional active elements. Because of the low input and high output impedance of the circuit for current signals and the high input and low output impedance for voltage signals, it can be used in cascade for realizing higher‐order filters. SPICE simulation results are given to verify the theoretical analysis. Copyright © 2008 John Wiley & Sons, Ltd.     

Generation of current mode filters using NAM expansion

Systematic synthesis method to generate a family of current mode band‐pass–low‐pass circuits based on nodal admittance matrix (NAM) expansion is given. Eight equivalent circuits are obtained, five of them are new. Each of the generated circuits uses two grounded capacitors and three grounded resistors and two balanced output current conveyor (BOCCII) or two balanced output inverting current conveyor (BOICCII) or a combination of the two types. Generation of a low input impedance current mode band‐pass–low‐pass circuits based on NAM expansion results in 16 equivalent circuits. The NAM expansion is also used to generate 32 equivalent current mode universal filters using four BOCCII or BOICCII or a combination of the two types. Copyright © 2010 John Wiley & Sons, Ltd.     

A novel circuit element and its application in signal amplification

A novel IC‐based current amplifier configuration for signal‐processing applications that can be configured using commercially available integrated circuit elements is presented. The circuit is accurate, has a wide bandwidth and can drive grounded loads. It utilizes a CCII+ type current conveyor with its input circuit in the feedback loop of a current feedback amplifier (CFA). In the current amplifying mode, the circuit has a low input impedance over a broad frequency range which never rises above the low input impedance of the inverting input of the associated CFA. Experimental results obtained using AD844s confirm the results derived. Copyright © 2007 John Wiley & Sons, Ltd.