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A Review of Current Differencing Buffered Amplifiers: Performance Metrics and Technological Advances
Current Differencing Buffered Amplifiers (CDBAs) are a critical class of analog circuit components capable of handling both current and voltage signals with minimal power consumption. Due to their low impedance voltage output, they play a significant role in modern electronics for developing high-performance, high-precision analog and mixed-signal circuits. But, designing and characterizing CDBAs pose several challenges, such as ensuring stability at high frequencies, minimizing noise impact for high-precision applications, and enhancing adaptability. Integrating CDBAs with other analog components to create multifunctional integrated circuits opens many opportunities in the analog signal-processing domain. This paper reviews the evolution and applications of CDBAs in analog signal processing. Various implementation schemes, including those using commercial Current Feedback Amplifiers (CFAs) and novel CMOS configurations, are analyzed for their performance metrics such as supply voltage, power dissipation, input/output impedances, and technology node. Future trends and challenges in advancing CDBA technology towards higher integration and lower-voltage operation are discussed, highlighting potential applications in next-generation electronics.
Journal Article
Graphical Approach to Optimization of Maximally Efficient-Gain-Boosted Feedback Amplifiers
It is challenging to design high-gain amplifiers near the maximum oscillation frequency (fmax) of the transistors. This paper presents a comprehensive graphical approach to maximize the gain of feedback amplifiers with maximally efficient gain (GME) conception at near-fmax frequency. The complex gain-plane and the reflection-coefficient-plane are utilized to provide clear insights into both the gain and stability states of the two-port device while boosting GME. An efficient flowchart to synthesize feedback amplifiers is given, which optimizes the GME of a two-port device while ensuring the stability. A 210 GHz power amplifier in 40 nm CMOS was designed and optimized based on the proposed approach. The feedback circuit of the transistor pushes it to become potentially unstable and boosts GME. The measured peak small-signal gain was 10.48 dB at 195.33 GHz. The measured saturation output power and large-signal gain at 210 GHz were 3.04 dBm and 7.08 dB, respectively. The presented method could facilitate terahertz amplifier design.
Journal Article
A Review of Modern CMOS Transimpedance Amplifiers for OTDR Applications
The work presents a review of modern CMOS transimpedance amplifiers (TIAs) in the context of their application for low-cost optical time-domain reflectometry (OTDR). After introducing the basic principles behind the OTDR, the requirements for a suitable CMOS TIA are presented and discussed. A concise review of several basic TIA topologies is provided with a brief overview of their main properties. A detailed discussion is given on a representative set of approaches reported in the literature and the figure of merit (FOM) is introduced as a unified basis for performance comparison. Limitations of a single FOM as a basis for comparison are pointed out. Based on the provided discussion, some suggestions are made on the suitability of the TIA topologies for OTDR applications.
Journal Article
Compact inductorless CMOS low-noise amplifier for reconfigurable radio
A compact reconfigurable CMOS low-noise amplifier (LNA) is presented for applications in DCS1800, UMTS, WLAN-b/g and Bluetooth standards. The proposed LNA features first a current reuse shunt-feedback amplifier for wideband input matching, low-noise figure and small area. Secondly, a cascode amplifier with a tunable active LC resonator is added for high gain and continuous tuning of bands. Fabricated in a 0.13 μm CMOS process, the measured results show >20 dB power gain, <3.5 dB noise figure in the frequency range of 1.8–2.4 GHz, return losses S11 and S22 lower than −12 and −14 dB, respectively, with a moderate IIP3 of −11.8 dBm at 2.4 GHz. It consumes 9.6 mW from a 1.2 V supply voltage, while occupying an active silicon area of only 0.052 mm2.
Journal Article
Implementation and Experimental Verification of Resistorless Fractional-Order Basic Filters
Novel structures of fractional-order differentiation and integration stages are presented in this work, where passive resistors are not required for their implementation. This has been achieved by considering the inherent resistive behavior of fractional-order capacitors. The implementation of the presented stages is performed using a current feedback operational amplifier as active element and fractional-order capacitors based on multi-walled carbon nano-tubes. Basic filter and controller stages are realized using the introduced fundamental blocks, and their behavior is evaluated through experimental results.
Journal Article
Realization of Fractional-Order Current-Mode Multifunction Filter Based on MCFOA for Low-Frequency Applications
The present work proposes a novel fractional-order multifunction filter topology in current-mode (CM), which is designed based on the Modified Current Feedback Operational Amplifier (MCFOA). The proposed design simultaneously generates fractional-order low-pass (FO-LPF), high-pass (FO-HPF), and band-pass (FO-BPF) outputs while utilizing an optimized set of essential active and passive elements, thereby ensuring simplicity, cost efficiency, and compatibility with integrated circuits (ICs). The fractional-order feature allows precise control over the transition slope between the passband and the stopband, enhancing design flexibility. PSpice simulations validated the filter’s theoretical performance, confirming a 1 kHz cut-off frequency, making it suitable for VLF applications such as military communication and submarine navigation. Monte Carlo analyses demonstrate robustness against parameter variations, while a low THD, a wide dynamic range, and low power consumption highlight its efficiency for high-precision, low-power applications. This work offers a practical and adaptable approach to fractional-order circuit design, with significant potential in communication, control, and biomedical systems.
Journal Article
Synthetic Transformer Design Using Commercially Available Active Components
In this study, a novel synthetic transformer (ST), namely mutually coupled circuit, using commercially available active components such as current feedback operational amplifiers (CFOAs) is proposed. The proposed ST uses four CFOAs, two grounded capacitors and five resistors. It possesses only resistors but no capacitors attached in series to W/X terminals of the CFOAs; consequently, its high-frequency performance is well. Nevertheless, it needs a single matching condition for symmetrical coupling. As an application example, a double-tuned band-pass filter is given. The validity of the proposed circuit is demonstrated through several SPICE simulations and experiments.
Journal Article
Novel four dimensional hyperchaotic system: analysis, adaptive control, analog and digital circuit design
In this paper, a new four-dimensional hyperchaotic system (HCS), with quadratic nonlinearities, has been proposed. The chaotic dynamical behaviors of the proposed system and its dynamic properties such as Lyapunov exponents, Kaplan Yorke dimension and dissipativity have been examined. To explore the proposed systems’ applications in communication world, adaptive self-synchronization scheme has also been put forward. The electronic realizability of the proposed system is examined in both analog and digital domains. The analog realization is based on Current Feedback Operational Amplifier (CFOA) while the Field Programmable Gate Array (FPGA) is used for digital one. The proposed HCS has some important features namely simple model, simple circuitry, minimum component count and sensitive with passive components that signifies the advantages for the signal processing circuit and its applications.
Journal Article
Further Generalization and Approximation of Fractional-Order Filters and Their Inverse Functions of the Second-Order Limiting Form
This paper proposes a further generalization of the fractional-order filters whose limiting form is that of the second-order filter. This new filter class can also be regarded as a superset of the recently reported power-law filters. An optimal approach incorporating constraints that restricts the real part of the roots of the numerator and denominator polynomials of the proposed rational approximant to negative values is formulated. Consequently, stable inverse filter characteristics can also be achieved using the suggested method. Accuracy of the proposed low-pass, high-pass, band-pass, and band-stop filters for various combinations of design parameters is evaluated using the absolute relative magnitude/phase error metrics. Current feedback operational amplifier-based circuit simulations validate the efficacy of the four types of designed filters and their inverse functions. Experimental results for the frequency and time-domain performances of the proposed fractional-order band-pass filter and its inverse counterpart are also presented.
Journal Article