Low Output Impedance Research Articles

A voltage-mode fully cascadable biquad with three CFOAs and grounded capacitors

In this paper, a new voltage-mode second-order multifunction filter with three current feedback operational amplifiers is developed. This circuit generates low-pass filter, band-pass filter (BPF), inverting-type BPF, notch filter, and all-pass filter (APF) responses with all gains. It has high input and low output impedances for all the filter responses. It also has the advantage of grounded two capacitors, which is essential for integrated circuit technology. It has orthogonally controllable features for all the filter responses except the APF one. However, one passive element matching condition is needed to obtain an APF response. Many simulations are carried out via the SPICE program, where 0.13 µm technology parameters are utilized. Furthermore, a few experiments are performed using the AD844s to see the performance of the developed filter in practice.

Updates on Impact Ionisation Triggering of Thyristors

High voltage (HV) generators are used in multiple industrial and scientific facilities. Recent publications have demonstrated that triggering industrial thyristors (relatively slow switching devices) in overvoltage mode, also called impact ionization mode, significantly enhances their dU/dt and dI/dt characteristics. This novel triggering methodology necessitates the application of substantial overvoltage between the thyristor’s anode and cathode, delivered with a swift slew rate exceeding 1 kV/ns. The adoption of compact pulse generators constructed from commercially available off-the-shelf components (COTS) opens up avenues for deploying this technology across various domains, including the implementation of high-speed kicker generators in particle accelerators. In our methodology, we employed commercially available high-voltage SiC MOSFETs along with a custom-designed fast gate driver. This driver was conceptualized based on the recent development of gate boosting techniques, featuring a driving voltage exceeding 600 V. The gate driver for these MOSFETs comprises three key components: a level-shifter with NMOS and PMOS transistors, a compact Marx generator with two avalanche transistors, and a GaN HEMT in a high input and low output impedance configuration. The proposed gate-boosting driver achieves a slew rate exceeding 1 kV/ns for the driving pulse. Furthermore, we demonstrate that with this driver, a 1.7 kV rated SiC MOSFET can produce an output pulse of 1.45 kV and a maximum slew rate of ≈2.5 kV/ns. This gate-boosting driver aims to minimize commutation times, achieves a slew rate of over 1 kV/ns, and handle higher loads, making it ideal for impact ionization triggering of industrial thyristors.

Compact active analog device for novel applications useful for sensing and measurement

The presented research introduces a novel approach to modern modular active device and provides various practical application examples tailored for industrial sensing readouts. Straightforward implementation of single active device-based topologies in frequency bands from kHz up to MHz is presented. These applications include: an electronically linearly tunable special band-pass filter that can be easily modified into a voltage-controlled oscillator, a two-port quadratic transformer, an amplitude modulator, and an equalization circuit (which serves as a fractional-order differentiator and integrator). These circuits benefit from high-impedance voltage input and low-impedance output (easily matched to 50 Ω), high processed signal levels (often reaching hundreds of mV), and simplified topologies without redundant passive elements. These features are especially valuable in tunable and configurable solutions for modern communication, sensing, audio, and consumer electronic systems, as well as in modeling various physical and biological systems. The experiments have been provided by simulations and measurements using device VCA824.

A versatile plasma generation power supply featuring a multilevel converter for arbitrary waveforms generation

Purpose Plasma technology has become of great interest in a wide variety of industrial and domestic applications. Moreover, the application of plasma in the domestic field has increased in recent years due to its applications to surface treatment and disinfection. In this context, there is a significant need for versatile power generators able to generate a wide range of output voltage/current ranging from direct current (DC) to tens of kHz in the range of kVs. The purpose of this paper is to develop a highly versatile power converter for plasma generation based on a multilevel topology. Design/methodology/approach This paper proposes a versatile multilevel topology able to generate versatile output waveforms. The followed methodology includes simulation of the proposed architecture, design of the power electronics, control and magnetic elements and test laboratory tests after building an eight-level prototype. Findings The proposed converter has been designed and tested using an experimental prototype. The designed generator is able to operate at 10 kVpp output voltage and 10 kHz, proving the feasibility of the proposed approach. Originality/value The proposed converter enables versatile waveform generation, enabling advanced studies in plasma generation. Unlike previous proposals, the proposed converter features bidirectional operation, allowing to test complex reactive loads. Besides, complex waveforms can be generated, allowing testing complex patterns for optimized cold-plasma generation methods. Besides, unlike transformer- or resonant-network-based approaches, the proposed generator features very low output impedance regardless the operating point, exhibiting improved and reliable performance for different operating conditions.

Voltage-Mode Multifunction and Universal Biquads with Two CFOAs

In this paper, a new voltage-mode (VM) multifunction filter including only two grounded capacitors, three resistors, and two current feedback operational amplifiers is introduced. This filter with one high input impedance and two low output impedances can simultaneously provide band-pass filter (BPF) and low-pass filter (LPF) responses with an adjustable gain. A universal VM filter topology with three inputs and one output generating high-pass filter (HPF), BPF, LPF, notch filter, and all-pass filter (APF) responses is obtained from the multifunction one. It has the same number of active and passive elements as the multifunction and a low output impedance. Sensitivities of both introduced filters are low enough. However, the APF of the introduced universal filter has a passive element-matching problem. As an example, parasitic impedance effects are considered for the LPF of the universal filter, while non-ideal gain analyses are given for the HPF. To see how the introduced universal filter works, countless simulations are performed through the SPICE (Simulation Program with Integrated Circuit Emphasis) program in which 0.13 [Formula: see text]m IBM CMOS technology parameters are utilized. DC supply voltages are selected as ± 0.9 V. Also, several experiments using commercially available AD844s with ± 10 V supply voltages are carried out to see the performance.

Current feedback operational amplifier‐based fully orthogonal universal and multifunction filters

SummaryThis paper introduces a second‐order voltage‐mode (VM) multiple‐input single‐output (MISO) universal filter and a second‐order current‐mode (CM) single‐input multiple‐output (SIMO) multifunction filter. The introduced VM MISO universal filter includes a single current feedback operational amplifier (CFOA) and a single voltage follower as active elements, while the introduced CM SIMO multifunction filter contains two CFOAs. Both introduced circuits are orthogonally controllable. In other words, the quality factors can be controlled through a single resistor without affecting the resonance frequencies. Both circuits have low sensitivities and no passive element‐matching conditions. The introduced VM MISO universal filter has a low output impedance. Moreover, to extract the output currents of the proposed CM SIMO from high impedance terminals, second‐generation current conveyor‐based version of the circuit is introduced. Simulations are made through the PSPICE program, where 0.13‐μm IBM CMOS technology parameters are utilized. DC supply voltages are selected as ±0.9 V. In the experiments, AD844s are used, and DC supply voltages are chosen as ±7.5 V.

0.5-V 281-nW Versatile Mixed-Mode Filter Using Multiple-Input/Output Differential Difference Transconductance Amplifiers.

This paper presents a new low-voltage versatile mixed-mode filter which uses a multiple-input/output differential difference transconductance amplifier (MIMO-DDTA). The multiple-input of the DDTA is realized using a multiple-input bulk-driven MOS transistor (MI-BD-MOST) technique to maintain a single differential pair, thereby achieving simple structure with minimal power consumption. In a single topology, the proposed filter can provide five standard filtering functions (low-pass, high-pass, band-pass, band-stop, and all-pass) in four modes: voltage (VM), current (CM), transadmittance (TAM), and transimpedance (TIM). This provides the full capability of a mixed-mode filter (i.e., twenty filter functions). Moreover, the VM filter offers high-input and low-output impedances and the CM filter offers high-output impedance; therefore, no buffer circuit is needed. The natural frequency of all filtering functions can be electronically controlled by a setting current. The voltage supply is 0.5 V and for a 4 nA setting current, the power consumption of the filter was 281 nW. The filter is suitable for low-frequency biomedical and sensor applications that require extremely low supply voltages and nano-watt power consumption. For the VM low-pass filter, the dynamic range was 58.23 dB @ 1% total harmonic distortion. The proposed filter was designed and simulated in the Cadence Virtuoso System Design Platform using the 0.18 µm TSMC CMOS technology.

Enhanced Efficiency on ANPC-DAB through Adaptive Model Predictive Control

This work studies the DC-DC conversion stage in solid-state transformers (SST). The traditional two- or three-level dual active bridge (DAB) topology faces limitations in microgrid interconnection due to power and voltage limitations. For this reason, the use of multilevel topologies such as active neutral point clamped (ANPC) is a promising alternative. Additionally, the efficiency of the SSTs is a recurring concern, and reducing losses in the DC-DC stage is a subject to be studied. In this context, this work presents a new control technique based on an adaptive model- based predictive control (AMPC) to select the modulation technique of an ANPC-DAB DC-DC converter aimed at reducing losses and increasing efficiency. The single-phase shift (SPS), triangular, and trapezoidal modulation techniques are used according to the converter output power with the aim of maximizing the number of soft-switching points per cycle. The performance of the proposed control technique is demonstrated through real-time simulation and a reduced-scale experimental setup. The findings indicate the effectiveness of the AMPC control technique in mitigating voltage source perturbations. This technique has low output impedance and is robust to converter parameter variations. Prototyping tests revealed that, in steady-state, the AMPC significantly improves converter efficiency without compromising dynamic performance. Despite its advantages, the computational cost of AMPC is not significantly higher than that of traditional model predictive control (MPC), allowing for the allocation of time to other applications.

Optimization of Butterworth and Bessel Filter Parameters with Improved Tree-Seed Algorithm.

Filters are electrical circuits or networks that filter out unwanted signals. In these circuits, signals are permeable in a certain frequency range. Attenuation occurs in signals outside this frequency range. There are two types of filters: passive and active. Active filters consist of passive and active components, including transistors and operational amplifiers, but also require a power supply. In contrast, passive filters only consist of resistors and capacitors. Therefore, active filters are capable of generating signal gain and possess the benefit of high-input and low-output impedance. In order for active filters to be more functional, the parameters of the resistors and capacitors in the circuit must be at optimum values. Therefore, the active filter is discussed in this study. In this study, the tree seed algorithm (TSA), a plant-based optimization algorithm, is used to optimize the parameters of filters with tenth-order Butterworth and Bessel topology. In order to improve the performance of the TSA for filter parameter optimization, opposition-based learning (OBL) is added to TSA to form an improved TSA (I-TSA). The results obtained are compared with both basic TSA and some algorithms. The experimental results show that the I-TSA method is applicable to this problem by performing a successful prediction process.

New Current-Mode Precision Full-Wave Rectifier Employing Single Inverted Z-Copy Current Differencing Buffered Amplifier

This paper aims to introduce a new current-mode precision full-wave rectifier configuration using a single inverted Z-copy current differencing buffered amplifier (IZC-CDBA) and two nMOSFETs. The unique feature of the proposed configuration is that it can simultaneously produce both the inverting and non-inverting rectified outputs without changing its architecture. Only active components make the configuration more suited for IC implementation. Moreover, it features low input impedance and high output impedance, making it fully cascadable. In addition, the new design enjoys extremely high-frequency operations. The effects of non-ideal transfer gain and parasitic impedances on the designed circuit are also explored. PSPICE simulations test the functionality of the proposed circuit for two distinct types of IZC-CDBA realization. The CMOS-based realization is checked through TSMC 0.18 μm level-7 technology parameters. The average DC current output, input dynamic range (± 450 μA), power consumption, temperature, total harmonic distortion, noise, and Monte-Carlo studies are performed to judge the efficiency level. The findings of the simulations match up nicely with the theoretical analysis. RMS and average value computation for a sinusoidal signal are also provided as an application of the suggested full-wave rectifier.

Design and Verification of a New Universal Active Filter Based on the Current Feedback Operational Amplifier and Commercial AD844 Integrated Circuit.

This paper presents a triple-input and four-output type voltage-mode universal active filter based on three current-feedback operational amplifiers (CFOAs). The filter employs three CFOAs, two grounded capacitors, and six resistors. The filter structure has three high-input and three low-output impedances that simultaneously provide band-reject, high-pass, low-pass, and band-pass filtering functions with single-input and four-output type and also implements an all-pass filtering function by connecting three input signals to one input without the use of voltage inverters or switches. The same circuit configuration enables two unique filtering functions: low-pass notch and high-pass notch. Three CFOAs with three high-input and low-output impedance terminals enable cascading without voltage buffers. The circuit is implemented using three commercial off-the-shelf AD844 integrated circuits, two grounded capacitors, and six resistors and further implemented as a CFOA-based chip using three CFOAs, two grounded capacitors, and six resistors. The CFOA-based chip has lower power consumption and higher integration than the AD844-based filter. The circuit was simulated using OrCAD PSpice to verify the AD844-based filter and Synopsys HSpice for post-layout simulation of the CFOA-based chip. The theoretical analysis is validated and confirmed by measurements on an AD844-based filter and a CFOA-based chip.

Realization of a new PMOS transistors based first-order delay equalizer suitable for communication networks

In this paper, a novel first-order delay equalizer based on a PMOS transistor is proposed which is highly suitable for the communication systems and networks. The core circuit consists of three unity-gain PMOS inverting amplifiers, one resistor and one capacitor. The newly proposed delay equalizer has ability to provide both inverting all pass and non-inverting all pass responses simultaneously from the same structure without restriction of any matching of passive elements to achieve desired performance. High input and low output impedances enable cascadability in the proposed circuit. The circuit's behaviour under loading effects and the effect of parasitic components are also examined in detail. To assess the applicability of the proposed structure, nth-order delay equalizer is also presented. The performance of the proposed work is validated through PSPICE simulations utilizing TSMC 0.18 μm level-7 CMOS technology process parameters, with voltage levels set at ±0.9 V. Furthermore, real-time post-layout verification is being carried out to ensure the confirmed performance.

THE RESONANT AMPLIFIER OF THE ACTIVE ELECTRICAL POWER WITH ADDITIONAL VOLTAGE SOURCE. SUGGESTIONS, ANALYSIS, NUMERICAL ESTIMATES

The problem of increasing energy saving in industry leads to the need to develop new technical devices. The paper presents and analyzes the circuit of the resonance amplifier of active electric power, evaluates the characteristics of electromagnetic processes for the fundamental substantiation of the operation of real devices based on this circuit. Mathematical analysis of electromagnetic processes taking place was carried out using strict methods of the theory of electric circuits. The advantages of this scheme in comparison with similar previous proposals are shown. The device includes four active-reactive circuits that are inductively connected. The first of them is an input circuit with a harmonic signal source that needs to be amplified. The second circuit generates enhanced reactive power in the "voltage resonance" mode. The third circuit with an additional voltage source provides reactive power output from the second circuit in the "resonance of currents" mode without adverse effects on amplification processes. The fourth circuit, inductively connected to the third circuit, contains an output load - a resistor that simulates the allocation of active power. On the basis of the analysis and numerical evaluation of the characteristics of the processes taking place in the proposed scheme of the resonance amplifier of active electric power, its basic efficiency is shown. The calculations of the experimental model made it possible to formulate recommendations for the selection of circuit elements of a working resonant amplifier with a high efficiency for low-impedance output loads. The considered real parameters of the device make it possible to minimize the dissipation of the energy of converted electrical signals and to increase the amplification factor of the electric power of harmonic currents and voltage by choosing the element base. The obtained results can be considered as practical recommendations for the creation of real devices for amplifying active electric power for use in various industries.

Physical Human–Robot Interaction Control of Variable Stiffness Exoskeleton With sEMG-Based Torque Estimation

Robotic exoskeleton assistance is an effective method for the treatment of patients with movement disorders. Firstly, this paper presents a variable stiffness knee exoskeleton robot (VS-KExo), which can independently control stiffness and position and has a large stiffness range under low preload. Then, combined with the designed variable stiffness exoskeleton, a physical human-robot interaction (pHRI) control scheme based on joint torque estimation is proposed. Different from previous studies, this method uses the mechanical properties of the exoskeleton to achieve pHRI without complex control algorithms and force/torque sensors. Furthermore, the joint torque is estimated based on the surface electromyography signal (sEMG) and the Hill-based muscle model, and the exoskeleton can realize assist-as-needed (AAN) function: 1) when the subject trains with less effort, the exoskeleton maintains a high output physical impedance to provide high tracking accuracy; and 2) when the subject trains with greater effort, the exoskeleton maintains a low output impedance to provide high physical compliance. Finally, we conducted experiments on three healthy subjects and two subjects with lower limb motor dysfunction to verify the effectiveness of the torque estimation method and the pHRI control scheme.

A Flexible, 2.4‐GHz Wireless Ion Sensor System Using Printed Organic Amplifiers with 3‐V Single Supply

AbstractIntegration of organic thin‐film transistor (OTFT) devices with a wireless data transmission system such as 2.4‐GHz Bluetooth low energy (BLE) is a significant requirement for activating the Internet of Thing (IoT) ecosystem based on a vast number of sensors, while conventional OTFT circuits have problems with their high output impedance and the need for multiple power supplies. Here, a wireless, real‐time, and flexible sodium ion sensing system composed of a printed Na+ sensor, printed OTFT‐based amplifiers, inorganic passive elements, a BLE module, and a 3‐V sheet‐type battery is demonstrated. The printed organic amplifier circuits based on dual threshold technology and dual‐gate structure are combinable with a BLE module because of their low output impedance of 50 kΩ and operate with 3‐V single supply as well as improving operational stability under illumination. The sensitivity to Na+ concentration is improved from 53.7 to 242.5 mV dec−1 (4.5 times higher) by the OTFT‐based amplifier, and the data is transmitted in real‐time to a tablet via the BLE wireless communication.

A New Low-Voltage Second Generation Voltage Conveyor Using Merged Voltage Follower and DTMOS Techniques

A very simple, compact and low-power second generation voltage conveyor circuit using only eight transistors is proposed in this work. Voltage follower stage is implemented using merged voltage follower (MVF), offering very low output impedance. A simple current mirror forms the input stage of the proposed voltage conveyor. To further enhance the linearity, another circuit is proposed where input transistor in MVF is replaced with DTMOS (Dynamic Threshold Voltage MOSFET), giving [Formula: see text][Formula: see text]mV linearity range as compared to [Formula: see text][Formula: see text]mV of the first proposal. Proposed-II VCII provides reduced offset voltage due to decreased effective threshold of DTMOS, and gain bandwidth product of the circuit also improves. Simulation results are computed using 180-nmCMOS technology with supply voltage of [Formula: see text][Formula: see text]V to validate the proposed circuits. Proposed-I and proposed-II VCII consume 85.1[Formula: see text][Formula: see text]W and 97.5[Formula: see text][Formula: see text]W, respectively. An application of the proposed conveyors as “current to voltage converter”, is also presented.

0.3-V Voltage-Mode Versatile First-Order Analog Filter Using Multiple-Input DDTAs.

This paper presents a versatile first-order analog filter using differential difference transconductance amplifiers (DDTAs). The DDTA employs the bulk-driven (BD) multiple-input MOS transistors technique (MI-MOST) operating in the subthreshold region. This results in low-voltage and low-power operational capability. Therefore, the DDTA, designed using 130 nm CMOS technology from UMC in the Cadence environment, operates with 0.3 V and consumes 357.4 nW. Unlike previous works, the proposed versatile first-order analog filter provides first-order transfer functions of low-pass, high-pass, and all-pass filters within a single topology. The non-inverting, inverting, and voltage gain of the transfer functions are available for all filters. Furthermore, the proposed structure provides high-input and low-output impedance, which is required for voltage-mode circuits. The pole frequency and voltage gain of the filters can be electronically controlled. The total harmonic distortion of the low-pass filter was calculated as -39.97 dB with an applied sine wave input signal of 50 mVpp@ 50 Hz. The proposed filter has been used to realize a quadrature oscillator to confirm the advantages of the new structure.

Ferroelectric Modulation in Flexible Lead-Free Perovskite Schottky Direct-Current Nanogenerator for Capsule-Like Magnetic Suspension Sensor.

The tribovoltaic nanogenerator (TVNG), a promising semiconductor energy technology, displays outstanding advantages such as low matching impedance and continuous direct-current output. However, the lack of controllable and stable performance modulation strategies is still a major bottleneck that impedes further practical applications of TVNG. Herein, by leveraging the ferroelectricity-enhanced mechanism and the control of interfacial energy band bending, a lead-free perovskite-based (3,3-difluorocyclobutylammonium)2 CuCl4 ((DF-CBA)2 CuCl4 )/Al Schottky junction TVNG is constructed. The multiaxial ferroelectricity of (DF-CBA)2 CuCl4 enables an excellent surface charge modulating capacity, realizing a high work function regulation of ≈0.7eV and over 15-fold current regulation (from 6 to 93µA) via an electrical poling control. The controllable electrical poling leads to elevated work function difference between the Al electrode and (DF-CBA)2 CuCl4 compared to traditional semiconductors and halide perovskites, which creates a stronger built-in electric field at the Schottky interface to enhance the electrical output. This TVNG device exhibits outstanding flexibility and long-term stability (>20000 cycles) that can endure extreme mechanical deformations, and can also be used in a capsule-like magnetic suspension device capable of detecting vibration and weights of different objects as well as harvesting energy from human motions and water waves.

Analytical assessment of sodium ISFET based sensors for sweat analysis

Body thermoregulation during exercise induces sweating with the consequent loss of water, electrolytes and other compounds. The use of sweat for bioanalytical purposes has recently widespread because it is an easily accessible biofluid that can be noninvasively collected and/or directly monitored using wearable devices. Different sweat biomarkers can be monitored as indicators of the physiological status of an individual. The concentration of sweat Na+ electrolyte provides information about dehydration or hyponatremia events. Among the different sensor technologies applied for Na+ ion detection in sweat, ion-sensitive field-effect transistors (ISFETs) show superior features in terms miniaturization, key for working with the low volumes of sweat available, robustness, scalability and reproducibility. They also offer fast response and low impedance output signal. This work reports an in-depth study that thoroughly assesses the potential of ISFET sensors for sweat Na+ analysis. Results show a reproducible sensitivity of 60.7 ± 0.5 mV (-Log aNa)− 1, high repeatability, and lifetime up to one month. Sensor reliability is demonstrated by analysing 20 sweat samples and results are compared with the ones provided with the standard ion chromatography technique (IC). The statistical analysis demonstrates that Na+ concentrations estimated with the ISFET sensor and IC are in good agreement showing a relative error of up to 20%. Results demonstrate that the sensor presented in this work can potentially be used for the continuous monitoring of Na+ changes in sweat during exercise.

A High Performance 0.3 V Standard-Cell-Based OTA Suitable for Automatic Layout Flow

In this paper, we propose a novel standard-cell-based OTA architecture based on an improved version of the differential to single-ended converter, previously proposed by the authors, on a novel standard-cell-based basic voltage amplifier block. Due to a replica-bias approach, the basic voltage amplifier exhibits a well-defined output static voltage to allow easy cascadability. Another feature of the basic voltage amplifier is to provide a low output impedance to allow dominant pole compensation at the output of the cascade of several stages. An ultra-low voltage (ULV) standard-cell-based OTA based on the proposed architecture and building blocks has been designed referring to the standard-cell library of a 130-nm CMOS process with a supply voltage of 0.3 V. The layout of the OTA has been implemented by following an automatic layout flow within a commercial tool for the place-and-route of digital circuits. Simulation results have shown a differential gain of 50 dB with a gain–bandwidth product of 10 MHz when driving a 150 pF load capacitance. Good robustness is achieved under PVT variations, in particular for voltage gain, offset voltage, and phase margin. State-of-the-art small signal figures of merit and limited area footprint are key characteristics of the proposed amplifier.