Amplifier Output Stage Research Articles

Converting Ambipolar Double‐Walled Nanotube Bundles to Unipolar Carbon Nanotube Field‐Effect Transistor Devices by Inner Functionalization

Carbon nanotube (CNT)‐based transistor devices have been demonstrated and are seen as the next‐generation alternative to replace the current generation electronic devices based on silicon MOS technology. Their limitations, however, are related to their instability in ambient conditions and technical challenges in scaling up production of individual CNT devices. Herein, a simple technique to convert ambipolar (both n‐ and p‐carrier) individual CNT‐based transistors into unipolar (p‐type carrier) transistors that carry large currents ≈±7 mA before saturation is demonstrated. Such large current‐carrying capability from an individual or single‐bundle CNTs will be ideal for applications that require high currents such as output stages of radio frequency (RF) and audio amplifiers. This work highlights the ability to tune CNT‐based transistor devices to suit specific applications, which is essential for the development of next generation of nanoelectronics.

An enhanced ultra-wideband single phase hybrid supply envelope tracking modulator for modern wireless communications

This paper presents a Single Phase Hybrid Supply Envelope tracking Modulator (HSEM) for RF-Power Amplifiers (RF-PAs) used in modern wireless communication systems such as 5G and 6G applications. The proposed HSEM consists of an ultra-wideband linear amplifier to track the input signals with several Mega Hertz of bandwidth, a switching amplifier to provide a high-efficiency supply voltage for the main power amplifier, and a new sensing circuit to generate the required voltage for the switching amplifier. The designed HSEM uses a two-stage rail-to-rail linear class-AB amplifier with constant Gm, high gain bandwidth (GBW), high slew rate (SR), and good phase margin (PM). Most conventional modulators use a sensing resistor or a resistor structure that increases the output ripple and the power loss. The proposed structure uses a linear amplifier output stage sensing circuit and a hysteresis low power current comparator without any resistors, external capacitors, filters, or multi-phase modulator structures. Additionally, using a current comparator eliminates the need for an external reference voltage or a current-to-voltage converter. The proposed structure does not need to remove the switching ripple through the linear amplifier, leading to a more relaxed linear amplifier design. A comprehensive analysis and guide on how to optimally select the inductor values, and the mathematical equation for the switching frequency of the hybrid modulator is given. The efficiency of the proposed structure is 84.3 %, and the maximum output power is 27.3dBm. The average output ripple is 4.16 mV in the wide range of the input voltages, and its minimum is 0.4 mV. In addition, the new structure can track a signal with 400 MHz bandwidth with FOM of the HSEM about 18. The proposed modulator is suitable for broadband and emerging telecommunications applications such as 5G and 6G, and as a power supply for RF power amplifiers. The proposed HSEM is evaluated with TSMC 180 nm CMOS technology parameters.

ANALYSIS AND DEVELOPMENT OF BRIDGE SCHEMES FOR JET POWER CONTROL

Reactive power compensation is one of the components of improving the efficiency of electrical networks, the theoretical foundations of which were developed at the beginning of the last century by Frieze and Budenau. However, the development of effective control algorithms for reactive power compensation devices continues today. It is conducted in two directions - increasing the efficiency of the compensation process, which is mainly determined by the inertia of the control algorithm, and finding effective and compact methods for describing the components of the power of the electrical network. At present, the p-q instantaneous power theory proposed by Akagi and a number of other theories is widely used. The transition to electronic control methods of power devices, such as electric drive, radio transmitting devices - has dramatically increased the efficiency of such systems, but set an urgent task to ensure optimal conditions for power transmission to load, ie coordination of output stages of power amplifiers and actuators. Such coordination is provided at compensation of reactive components in output circles. To implement this task, it is advisable to use a controlled inductance and capacitance. At the same time, the use of traditional solutions used by varicaps or reactive transistors is limited by the technological possibilities of using varicaps at high reactive capacities. The use of an external power supply is a significant disadvantage, limiting the scope of controlled reactivity based on reactive transistors. Setting the DC mode of controlled reactivity transistors requires the use of additional batteries, blocking and filtering, which reduces the reliability of the device. The use of additional power supplies also reduces the energy efficiency of the device as a whole and limits the use of such devices only to low-power electronic components: frequency modulators, frequency tuners, etc. In power electronics, the power of controlled reactivity is energy inefficient.

High-frequency power amplifier output stage automatic control circuit

High-frequency power amplifier output stage automatic control circuit

A 28-GHz 16-Gb/s High Efficiency 16-QAM Transmitter in 65-nm CMOS

This work presents the design and implementation of an ultra-broadband quadrature common-mode amplitude modulator (QCAM) to generate high power back-off efficiency 16-QAM signals. The proposed QCAM transmitter consists of I- and Q-path PAM4 modulators, which digitally modulate the power amplifier (PA) output stage to relax the linearity requirement. An interleaved differential transformer-based coupler is proposed for wide-band combination of the baseband and LO signals. The I and Q PAM4 signals are combined using an on-chip Wilkinson power combiner to generate the 16-QAM output signal. The 28-GHz 16-QAM transmitter test chip, implemented in 65-nm CMOS, achieved measurement results of 11.35 dBm average RF output power, 9.2% DC-RF efficiency, 16 Gb/s data rate, and −24 dB EVM.

Общий подход к построению математических моделей и алгоритмов для решения прямых и обратных задач для сервопривода жидкости с управлением дроссельной заслонкой

It is pointed out that direct and inverse parametric problems on fluid servo drives with throttle control of energy flows (FSD/T) are usually dealt with using various mathematical models and packages of application computer programs depending on the solution objectives, established drive structure and design, and the type of input information signal. An FSD/T with a mechanical signal is known as a hydromechanical servo drive(HMSD/T), and that with an electrical is known as an electrohydraulical servo drive (EHSD/T). Special-purpose fluid servo drives with throttle control that use a combined signal are also possible. The variety of models is a factor that adds difficulty to development of algorithms and use of the obtained information; in particular, when transition from direct to inverse scenarios is made. At the same time, whatever the type of information signal, the drive structure contains the same energy loop, namely, a combination of the hydraulic amplifier output stage and a hydraulic motor. It is exactly this loop that determines the FSD/T power and dynamic performance characteristics. A universal mathematical model of a single-channel FSD/T, which is equally effective for solving direct and inverse problems as applied to HMSD/T and EHSD/T, is presented. The peculiarities of writing the universal model for HMSD/T and EHSD/T are considered in detail; a block diagram of implementing the software package for numerically solving direct and inverse problems is given, and algorithms for solving direct and inverse parametric problems for this model are presented. A universal algorithm and block diagram for solving the direct and inverse Pareto optimization problem for some particular competition parameters are drawn up. The advantages of using the universal model for the real optimization design of this class of drives are shown.

Tapered erbium-doped fibre laser system delivering 10 MW of peak power

We consider a fibre laser system generating ∼10-μJ, ∼500-fs pulses with a peak power of ∼10 MW at a repetition rate of 100 kHz and emission wavelength of 1.56 μm. The system is based on a master oscillator – power amplifier configuration. The amplifier ensures chirped-pulse amplification. The pulses are then compressed by a dispersive grating compressor. The output amplifier stage is based on a specially designed tapered large mode area erbium-doped fibre for suppressing nonlinear effects. The experimental data agree with numerical simulation results for the stretcher, amplifier and compressor. The stretcher and amplifier have been simulated using a generalised nonlinear Schrödinger equation. In addition, numerical simulation results suggest that optimising the stretcher and compressor will potentially allow the peak power of the system to be scaled up to ∼30 MW.

A Priori Error Bound for Moment Matching Approximants of Thermal Models

This article focuses on the moment matching methodology for deriving dynamic compact thermal models (DCTMs) of electronic components. For the first time, an a priori error bound is theoretically established both in the time and frequency domains, which is suited to accurately estimate the approximation error introduced by DCTMs in practical electronics applications. By exploiting this result, it is also shown that the near-optimal choice of matching points previously proposed by one of the authors minimizes the error bound here derived, among all the possible choices of matching points. The introduced error bound is verified by applying the moment matching algorithm to a state-of-the-art packaged InGaP/GaAs heterojunction bipolar transistor (HBT) used in output stages of power amplifiers for handset applications.

Automation of S-parameters measurements of high-power microwave transistors in a contact device with tunable strip matching circuits

In the practice by microwave power transistor amplifiers developing, the variable load method is usually used to determine the impedances of matching circuits in the complex conjugate matching mode. This solution involves the use of expensive equipment - coaxial impedance tuners and contact devices for mounting transistors in low impedance strip lines. An even more complicated and expensive way is the concept of X- parameters, based on the use of unique measuring equipment - a non-linear vector network analyzer, and a simulator for non-linear circuits design. The article proposes an alternative solution adapted to the operation of the transistor in real conditions and allowing to design the output stages of microwave power amplifiers using analysis and optimization of linear electrical circuits. The essence of the proposed solution is to automate the measurement of non-linear S-parameters of high-power microwave transistors in a contact device with tunable strip matching circuits for various DC supply voltage, frequency and input power mode in case of continuous or pulse input signal. The nonlinear S-parameters of the contact device are measured using the method of spatially remote variable load in the frequency range, in which the line conditioning and the maximum output power are achieved. The minimum of the reflected wave amplitude and the maximum gain are reached using movable strip matching transformers. The S-parameters measured in the coaxial line are automatically recalculated to the physical boundaries of the transistor by registering the positions of the input and output strip transformers.

Optimisation of the parameters of a broadband multibeam-pumped optical parametric amplifier

We report the results of the numerical simulation of the output amplifier stage of a high-power laser system based on parametric amplification of femtosecond pulses in an LBO crystal under multibeam pumping. A technique is described for choosing an optimal amplifier configuration with an arbitrary number of pump beams to provide a wide spectral gain band with a minimum loss due to parametric diffraction. The results of simulating the parametric amplification, amplification efficiency, and spatial profile of amplified radiation with allowance for the interference of amplified parasitic beams are presented. A possibility of eliminating the spatial modulation of the amplified radiation intensity, which occurs when using spatial filters, is demonstrated. An increase in the number of pump beams is found to rise the amplified pulse duration, slightly (from 20 to 21 fs) for incoherent pump beams and more significantly (to 25 fs) for coherent beams. The amplification efficiency is reduced from 23% to 21% in the former case and to 11% in the latter case.

Power amplifier circuits for functional electrical stimulation systems

Abstract Introduction: Functional electrical stimulation (FES) is a technique that has been successfully employed in rehabilitation treatment to mitigate problems after spinal cord injury (SCI). One of the most relevant modules in a typical FES system is the power or output amplifier stage, which is responsible for the application of voltage or current pulses of proper intensity to the biological tissue, applied noninvasively via electrodes, placed on the skin surface or inside the muscular tissue, closer to the nervous fibers. The goals of this paper are to describe and discuss about the main power output designs usually employed in transcutaneous functional electrical stimulators as well as safety precautions taken to protect patients. Methods A systematic review investigated the circuits of papers published in IEEE Xplore and ScienceDirect databases from 2000 to 2016. The query terms were “((FES or Functional electric stimulator) and (circuit or design))” with 274 papers retrieved from IEEE Xplore and 29 from ScienceDirect. After the application of exclusion criteria the amount of papers decreased to 9 and 2 from IEEE Xplore and ScienceDirect, respectively. One paper was inserted in the results as a technological contribution to the field. Therefore, 12 papers presented power stage circuits suitable to stimulate great muscles. Discussion The retrieved results presented relevant circuits with different electronic strategies and circuit components. Some of them considered patient safety strategies or aimed to preserve muscle homeostasis such as biphasic current application, which prevents charge accumulation in stimulated tissues as well as circuits that dealt with electrical impedance variation to keep the electrode-tissue interface within an electrochemical safe regime. The investigation revealed a predominance of design strategies using operational amplifiers in power circuits, current outputs, and safety methods to reduce risks of electrical hazards and discomfort to the individual submitted to FES application.

A low-noise programmable gain amplifier with fully balanced differential difference amplifier and class-AB output stage

A programmable gain amplifier (PGA) is presented, targeting amplifying input signal with high dynamic range and low noise. The proposed PGA adopts fully balanced differential difference amplifier (FBDDA) as main amplifier. A class-AB implementation of output stage is advantageous in order to achieve high current driving capability with very low quiescent power consumption. Combining resistor-feedback loop controlled by digital signal, the proposed PGA achieves a dB-linear gain range from 0 to 15dB with a gain step of 1dB. Compared with previous works, the theoretical analysis and measurement results prove that the proposed structure has lower noise. The circuit was designed and fabricated in SMIC 0.18µm 3.3V process, showing a gain error of less than 0.25dB, a third harmonic distortion (HD3) of better than −83dB and a thermal noise of 1.6 nv/Hz. The measurement results indicate that the PGA described here has a −3dB bandwidth of 387.5MHz at maximum gain of 15dB. The PGA occupies a chip area of 0.1mm2.

Low power complementary metal‐oxide semiconductor class‐G audio amplifier with gradual power supply switching

The architecture, design and implementation of a low power complementary metal-oxide semiconductor (CMOS) class-G audio amplifier with gradual power-supply switching (GPSS) are presented. The proposed class-G amplifier output stage strategically uses the parallel connection of a class-AB output stage operating from smaller supplies (V DDL/V SSL), and a class-C output stage (with crossover from V SSL to V DDL) operating from higher supplies (V DDH/V SSH). GPSS is achieved using an efficient biasing scheme with level shifters. Moreover, the proposed biasing scheme in conjunction with negative feedback enables low distortion during the power-supply transition. Experimentally, the class-G amplifier prototype achieves a −82.5 dB THD + N, a peak load power of 50 mW and a quiescent power consumption of 350 μW. The proposed class-G amplifier was implemented in a standard CMOS 90 nm technology and occupies an active silicon area of 0.08 mm2.

Fibre amplifier based on an ytterbium-doped active tapered fibre for the generation of megawatt peak power ultrashort optical pulses

We report a new ytterbium-doped active tapered fibre used in the output amplifier stage of a fibre laser system for the generation of megawatt peak power ultrashort pulses in the microjoule energy range. The tapered fibre is single-mode at its input end (core and cladding diameters of 10 and ) and multimode at its output end (diameters of 45 and ), but ultrashort pulses are amplified in a quasi-single-mode regime. Using a hybrid Er/Yb fibre system comprising an erbium master oscillator and amplifier at a wavelength near , a nonlinear wavelength converter to the range and a three-stage ytterbium-doped fibre amplifier, we obtained pulses of energy and duration, which were then compressed by a grating-pair dispersion compressor with 60 % efficiency to a duration, approaching the transform-limited pulse duration. The present experimental data agree well with numerical simulation results for pulse amplification in the three-stage amplifier.

Multi-Turn Transmit Coil to IncreaseB1Efficiency in Current Source Amplification

A multi-turn transmit surface coil design was presented to improve B1 efficiency when used with current source amplification. Three different coil designs driven by an on-coil current-mode class-D amplifier with current envelope feedback were tested on the benchtop and through imaging in a 1.5 T scanner. Case temperature of the power field-effect transistor at the amplifier output stage was measured to evaluate heat dissipation for the different current levels and coil configurations. In addition, a lower power rated device was tested to exploit the potential gain in B1 obtained with the multi-turn coil. As shown both on the benchtop and in a 1.5 T scanner, B1 was increased by almost 3-fold without increasing heat dissipation on the power device at the amplifier's output using a multi-turn surface coil. Similar gain was obtained when connecting a lower power rated field-effect transistor to the multi-turn coil. In addition to reduce heat dissipation per B1 in the device, higher B1 per current efficiency allows the use of field-effect transistors with lower current ratings and lower port capacitances, which could improve the overall performance of the on-coil current source transmit system.

On‐coil multiple channel transmit system based on class‐D amplification and pre‐amplification with current amplitude feedback

A complete high-efficiency transmit amplifier unit designed to be implemented in on-coil transmit arrays is presented. High power capability, low power dissipation, scalability, and cost minimization were some of the requirements imposed to the design. The system is composed of a current mode class-D amplifier output stage and a voltage mode class-D preamplification stage. The amplitude information of the radio frequency pulse was added through a customized step-down DC-DC converter with current amplitude feedback that connects to the current mode class-D stage. Benchtop measurements and imaging experiments were carried out to analyze system performance. Direct control of B1 was possible and its load sensitivity was reduced to less than 10% variation from unloaded to full loaded condition. When using the amplifiers in an array configuration, isolation above 20 dB was achieved between neighboring coils by the amplifier decoupling method. High output current operation of the transmitter was proved on the benchtop through output power measurements and in a 1.5T scanner through flip angle quantification. Finally, single and multiple channel excitations with the new hardware were demonstrated by receiving signal with the body coil of the scanner.

A Comparative Analysis of Peaking Methods for Output Stages of Broadband Amplifiers

This paper presents a general analysis of peaking methods in output stages of amplifiers for broadband communication systems. It is shown that common peaking methods, although providing significant signal bandwidth enhancement ratios (BWER), are limited to 30%-50% of their speed potential by output matching requirements. A modified T-coil peaking is analyzed which enhances both signal bandwidth and output matching frequency range by up to 200% compared to common peaking methods. A broadband amplifier using this inductive output matching with 69-GHz bandwidth implemented in a 0.25 μm SiGe BiCMOS technology is presented to prove the validity of the analysis.

Systems and methods for protection of audio amplifier circuits

Systems and methods for providing protection from failure events in a digital audio amplification system. One embodiment of the invention comprises a system having a digital amplifier controller, an amplifier output stage coupled to the controller and configured to receive audio signals from the controller, one or more sensors coupled to the output stage and one or more low-pass filters coupled to receive sensor signals from the one or more sensors. The low-pass filter is configured to filter the sensor signals and to provide the filtered sensor signals to the controller, which provides a programmable response to the filtered sensor signals. The response may range from not taking any action, to limiting the amplification of audio signals, to shutting down the system.

Class ad audio amplifier

An audio amplifier comprising a Class D audio amplifier having an input receiving an analog input signal, a pulse width modulation stage for converting the analog input signal to a pulse width modulated signal, a driver stage receiving the pulse width modulated signal and for producing a driver PWM signal and an output switching audio amplifier stage receiving the driver PWM signal and providing an amplified PWM signal; an output filter stage receiving the amplified PWM signal for converting the amplified PWM signal into an analog audio signal; and a linear output amplifier stage receiving as inputs the analog input signal and the output of the output filter stage, the output of the output filter stage serving to bias the linear output amplifier stage. In one embodiment, two floating power supplies are superimposed on the output of the filter stage for biasing the linear amplifier, one at a preset voltage above the output signal of the filter stage and a second at a preset voltage below the output of the filter stage. The linear output amplifier stage provides an analog output to a sound reproduction transducer.

Focus on sensors

Focus on sensors