Dc Amplifier Research Articles

Combining Imaging and Electrophysiology to Visualize and Record Spreading Depolarizations in Mice.

Spreading Depolarizations (SDs) are massive events in the brain that often go undetected due to their slow propagation through gray matter. Because SD detection can be elusive, it is optimally confirmed using multiple methods. This protocol describes methods for combining imaging and electrophysiology to detect SDs in a manner that most laboratories can reliably and easily adopt. SDs occur following traumatic brain injuries, stroke, subarachnoid hemorrhages, ischemia, and migraine aura. Historically, SDs have been recorded using DC amplifiers, which can resolve the slow extracellular shift and the depression in high-frequency activity. However, DC amplifiers are nearly impossible to use for chronic in vivo recordings. This protocol employs a common AC amplifier for in vivo electrophysiology recordings to confirm high-frequency depression, along with non-invasive imaging necessary to detect the propagating wave of SD. These methods can be reliably adopted and/or modified for most experimental approaches to confirm the presence or absence of SDs following brain injury.

Cryogenic bipolar low noise dc amplifier for low frequency applications

A low-noise bipolar differential dc amplifier was studied at temperatures of 300 and 77 K. It was shown that to ensure the best amplifier performance in terms of noise figure when the operating temperature decreases from 300 to 77 K, it is advisable to use the transistor in the mode of low currents not exceeding 2 mA. It has been established that lowering the operating temperature to 77 K leads to a decrease in the input resistance of the amplifier from a value of several kiloohms to 100 Ohms, the dynamic range increases from 80 to 85 dB, and the harmonic coefficient increases from 0.09% to 1%. In addition, lowering the operating temperature to 77 K has a significant effect on the noise properties of the amplifier: the spectral density of voltage noise decreases from 1 to 0.4 nV/Hz1/2, the spectral density of current noise increases from 2.5 to 9 pA/Hz1/2, while also The threshold frequencies of 1/f noise increase: for voltage from (0.1...10) to 20 Hz and for current from (10...100) to 1000 Hz. The possibility of using an amplifier for low-temperature measurements of samples with low input resistance is substantiated.

Calibration of Cyclic-Pipelined ADCs Using CMOS for Area-Efficiency

One of the principal obstacles in the development of pipeline analog-to-digital converters (ADCs) is the imprecision associated with residue amplification. Operational amplifiers (Op-Amps) that possess high gain and speed are recognized for their excessive power consumption, making them unsuitable for employment in proficient analog-to-digital converters (ADCs). The study presents a new method for foreground calibration that addresses amplification differences in cyclic-pipelined ADCs, reducing the need for internal amplifier DC gain. The calibration technique was applied to a cyclic-pipelined ADC with a sampling rate of 2 MS/s and 16-bit resolution. The design of this ADC was optimized for area efficiency, and its fabrication utilized 180 nm CMOS technology. The analog-to-digital converter (ADC) used a 5-bit resolution sub-ADC performing 4 cycles to reduce potential errors. Each cycle contained one bit of redundancy. A fixed-point iterative algorithm was used to find the exact gain for each amplifier. Simulation data shows a SINAD of 100. 6 dB, despite a 57 dB DC gain amplifier. The ADC's active area is 1. 8 mm2 at 30 consumption. 43 mW.

Research on the Polygraph: the CMOS Neural Amplifier

The polygraph is an effective piece of equipment to detect if the suspect is lying in order to track down the criminal. The paper simulates and sets up the host part of the polygraph in order to explain how the polygraph works and some fields to use it. And we successfully make a neural amplifier to show the way that the host amplifies neural signals, and has a low passband that can filter out high-frequency signals. The circuit has two parts the folded cascode amplifier DC gain is 64.56, the -3dB bandwidth is about 100kHz and the total current consumption is 4uA and the capacitive feedback amplifier passband gain is 40dB and the passband is from about 3Hz to 5kHz. It is of great value not only in the field of criminal investigation, but also in VR, artificial intelligence (AI), and mental health. Because it can record and let people observe human brain activity and emotional changes. What’s more, with its development of it, it can solve many small crimes automatically, which means police can have more time and energy to deal with difficult cases and society can be more stable.

Design and Implementation of Output Circuitry for Millimeter-wave Direct Detection Radiometer

This paper presents a design and an implementation of an output circuitry for a millimeter-wave direct detection radiometer. This circuitry is based on commercially available ultra-low-noise op-amp and consist of an active anti-aliasing filter and DC amplifier. The prototype of this circuitry has been realized and evaluated.

Macro Model for Discrete-Time Sigma‒Delta Modulators

This work presents a macro model for discrete-time sigma‒delta modulators, which can significantly reduce the simulation time compared to transistor level circuits. The proposed macro model is realized by effectively combining active and passive ideal circuit components with Verilog-A modules. As such, since the macro model is a true representation of the actual transistor level circuit, a moderately good accuracy can be obtained. In addition, the proposed macro model includes the major amplifier, comparator, and switch‒capacitor non-idealities of the sigma‒delta modulator such as amplifier DC gain, GBW, slewrate, comparator bandwidth, hysteresis, parasitic capacitance, and switch-on resistance. The results show the simulation time of the proposed macro model sigma‒delta modulator is only 6.43% of the transistor level circuit with comparable accuracy. As a result, the proposed macro model can facilitate the circuit design and leverage non-ideality analysis of discrete-time sigma‒delta modulators. As a practical design example, a second order discrete-time sigma‒delta modulator with a five-level quantizer is realized using the propose macro model for GSM and WCDMA applications.

THERMOSTABLE REFERENCE CURRENT AND VOLTAGE SOURCES FOR HIGH-LINEAR ANALOGUE-CODE-ANALOGUE SYSTEM

DC sources and reference voltage sources are widely used in various electronic devices: analog-to-digital and digital-to-analog converters, DC amplifiers, sample-and-hold devices, stabilized voltage sources, and others. At the same time, the accuracy and temperature characteristics of the latter largely depend on the same characteristics of direct current and voltage sources, which are subject to stringent requirements. There are quite a lot of different approaches to the construction of reference voltage and current source circuits with thermal compensation. The most famous of them – with the use of thermally compensated zener diodes operating in reverse breakdown mode. However, devices based on them have a high power consumption and low efficiency and a high level of noise, and it is difficult to implement temperature drift compensation due to a wide spread of temperature characteristics. The so-called bandgap circuits are also widely used – transistor reference voltage sources, the value of the reference voltage of which is determined by the band gap of the semiconductor. The most famous of them are Vidlar’s bandgaps and Brokau’s bandgaps. The specificity of all bandgap circuits is the rigid binding of the output voltage to the band gap of the semiconductor. The article proposes an alternative approach to the construction of direct current and voltage sources, which consists in the use of circuits of two-pole direct current sources. A new approach to the construction of thermally stable reference current sources based on bipolar transistors using the band gap voltage of a semiconductor and current mirrors is proposed. The principles of operation of the circuits are described and the possibility of achieving thermal compensation is proved. Computer modelling of the static characteristics of the proposed reference current sources, in particular, the temperature drift of the currents, has been carried out. A new approach to the construction of thermally stable reference voltage sources based on bipolar transistors with the use of thermally stable reference current generators is proposed. Analytical expressions are obtained that describe operation of circuits of reference voltage sources according to the proposed approach. A method for increasing the loading capacity of these reference voltage sources is proposed.

Static DC Transformer Based on Negative Capacitance and High Voltage Engineering

Abstract: For DC voltage amplification, the operational amplifier is mostly used in the non-inverting configuration. In this case, the DC voltage amplification is done using a negative capacitance converter. Since the feedback capacitor acts as an open circuit for DC signal, it provides isolation between input and output. The amplified voltage level is limited by the breakdown voltage of the transistors used to build the op-amp and further the insulation breakdown limit of the Miller capacitor. By making use of new technologies such as silicon carbide technology, the breakdown voltage of transistors can be made higher even 1.2 KV and combined with high voltage engineering for capacitive insulation such as polymer capacitors, this can become a huge breakthrough in electric power engineering. Additionally, it can be used as a effective DC source for electric vehicles. The nominal voltage used in hybrid vehicles ranges from 100V to 200V.For electric-only vehicles, the required voltage is as high as 800V.The simulations are done using MIT Circuit sandbox, an open source circuit simulation tool. Keywords: DC amplifier, Op-amp, negative capacitance, silicon carbide and high voltage insulation.

ПОСТРОЕНИЕ МОЩНЫХ ШИРОКОПОЛОСНЫХ УСИЛИТЕЛЕЙ ПОСТОЯННОГО ТОКА МОДУЛЯЦИОННОГО ТРАКТА ПЕРЕДАТЧИКОВ С РАЗДЕЛЬНЫМ УСИЛЕНИЕМ СОСТАВЛЯЮЩИХ

Increasing transmission path efficiency, as the largest consumer of electricity, is relevant for any wireless communication devices, digital television, and radio broadcasting. A number of methods are used to improve efficiency, including Envelope Tracking (ET) and Envelope Elimination and Restoration (EER, or Kahn method). Increasing the bandwidth of used frequencies in 5G radio systems requires expanding the modulation path DC amplifiers bandwidth to 250…500 MHz or more. The possibility of using amplifiers with input signal quantization (AISQ) as an alternative to the most common broadband hybrid modulators combining linear and switching (with PWM) amplification channels is considered. It is shown that in order to obtain AISQ high energy characteristics, it is advisable to perform, according to the scheme with output channels parallel connection, the switching of the amplifying cells along the input circuits and to reduce the saturation voltage on the output transistors. An approach has been developed for the AISQ characteristics optimizing according to the criterion of minimum losses. The example of AISQ parameters optimization and its energy characteristics calculation for a linearly increasing signal showed that, compared with a class B amplifier (n = 1), already with three-level quantization, the loss power in the AISQ decreases by 2...2.5 times (depending on the residual transistor voltage). A further increase in n leads to a less sharp decrease in the relative loss power, which, with the obvious complication of the circuitry implementation of such AISQ, makes the use of three-four-level quantization the most expedient. With these parameters, the AISQ becomes competitive with hybrid modulators and does not create electromagnetic interference from the PWM path.

Static and Dynamic Performance of Vector Control on Induction Motor with PID Controller: An Investigation on LabVIEW

A three-phase induction motor is often used in everyday life because of its high reliability. However, it is associated with some disadvantages, including difficulties in maintaining constant speed during load changes and speed regulation due to the decoupled system. Therefore, this study aims to adjust the three-phase induction motor control to become a separate amplifier DC motor by setting the vector control using the IFOC method, which changes the coupled to the decoupled system. The speed settings are equipped with a PID controller where its parameters, which are obtained using Ziegler Nichols, produce speed output with fast research time and small steady-state errors. This research was conducted to observe and analyze the performance of a controller based on the IFOC approach with a PID controller at speed differences, with static and dynamic conditions in the entire speed working area. In the first stage of the research, simulation is carried out with static conditions, namely changes in speed variations throughout the work area (low speed to high speed), the next stage is a simulation with dynamic conditions, which is to provide changes in the value of the load torque when the system is operating. The simulation result carried out with LabVIEW shows a response time of 1.13 ms, a settling time of 9.9 ms, and a steady error of 0.4% at the 500 Rpm set point. It also indicated dynamic characteristics with a recovery time of 4.9 ms at the 300 Rpm set point. When operated at low speed, IFOC with PID controller has a stable response. But In dynamic conditions, the use of a PID controller is considered unsuitable. This is because the PID controller is less fast and less robust in responding to the system when conditions change in the value of the load torque.

Simulation of the insulation monitoring system of the high-voltage electrical network of a vehicle with a hybrid power plant

The paper presents the results of mathematical and simulation modeling, as well as calculated and experimental dependencies, which make it possible to evaluate the operation of the insulation resistance monitoring system of the high-voltage power grid of a hybrid vehicle. The work also provides circuits for measuring insulation resistance, a mathematical model in the MATLAB Simulink environment, and the peculiarities of the operation of the software and hardware simulation complex. The aim of the work is to obtain the most reliable mathematical and physical model of insulation resistance, to determine the architecture of a high voltage battery with the IRM system included in it, to identify the key functions and characteristics of the IRM system, to test the simulation system. The introduction justifies the importance of the IRM system and provides references to standards that govern the requirements for measuring and identifying utility faults. The block diagram of the high voltage battery control system is presented. The composition of its main elements is described. The functions and key characteristics of the IRM system are considered, typical characteristics of insulation monitoring systems are given. A schematic diagram of determining the insulation resistance of conductors and an electric circuit is clearly considered. An equivalent circuit of a differential DC amplifier with a unipolar power supply is presented, which is used to amplify small differential voltages on a shunt when changing large common-mode voltages, which is part of the measuring circuit. Mathematical and simulation modeling was carried out to evaluate the method for calculating the insulation resistance according to the well-known scheme, which is used when measuring using the three-voltmeter method. There was considered the mode of checking the the insulation control system, when several test procedures performed containing simulation of the fault and operating condition of the insulation by connecting and measuring the test resistance. The results of physical simulation of the IRM system and measurement of insulation resistance, voltage between each of the high voltage supply wires and the high voltage battery case, voltage between the wires, battery voltage were obtained. The actual insulation resistance was calculated. The conclusions explain the effectiveness of physical and simulation modeling, obtaining a reliable mathematical model and low error in modeling the insulation characteristics.

High-precision nuclear-quadrupole-resonance thermometer for aerohydrodynamic research

In hydroaerodynamics, there are problems that require increased accuracy of temperature measurement. An example is the measurement of excess temperature at the periphery of turbulent jets. Unlimited temperature increase on the axis of the jet to increase the accuracy of measurement is impractical due to non-automodeliness by the Archimedes number. To do this, it is possible to use the phenomenon of nuclear quadrupole resonance. The device for exact measurement of temperature in the range from 0° C to +200 °C is offered. Using the LabView graphic programming package, a virtual model of an automatic thermometer based on nuclear quadrupole resonance in КClO3 was built. The temperature sensor is a superregenerative spectrometer with automatic monitoring of the center of the absorption line of the thermometric substance, consisting of the actual superregenerator, bandpass filter, comparator, DC amplifier and modulating voltage generator. The circuit that switches the supergenerator to the mode of continuous generation and output of information on the display contains a single vibrator, a buffer stage, a microcontroller and an indicator. From the output of the superregenerator, the absorption signal is fed to the bandpass filter, and then to the comparator. After the comparator, a voltage equal to the input voltage difference is amplified by a DC amplifier. This signal controls the resonant absorption frequency through the feedback circuit. The frequency of the sensor polling is determined by a single vibrator, the oscillations of which are synchronized with the clock generator. Measuring uncertainty in the range above changes from 0.02 K to 0.002 K It has been shown that either a manual frequency measurement method or a regenerative mode must be used to reduce the measurement uncertainty up to 0.002 K in the range. This improved automatic device is more complex, because of requirements of special measures to eliminate parasitic amplitude modulation. To increase the temperature range and precision, it is possible to find other thermometric substance, such as Сu2O crystals.

Vortex Express Method for Parameter Determination Thermoelectric Materials

The method is based on the possibility of determining the heat loss of electric power during the flow of Foucault eddy currents in the volume of a thermoelectric sample, placing in the field of action of the ferrite core an inductor through which electric currents that are symmetrical and asymmetric in nature flow sequentially in time.
 Mathematical expressions are obtained for the coefficients of electrical conductivity σ, thermal conductivity ϰ, thermo-emf α and thermoelectric figure of merit Z. Minimization of the error of the proposed method, carried out by computer simulation of the physical processes occurring in the sample using appropriate programs, showed that the operating frequency of the device measuring sensors should be located in the range of 36 ÷ 250 kHz, and the electric current flowing through it — taking into account the inequality qф/П/ qф/ qϰ > 10. The magnetic field induction ratio in terms of components is selected from the condition В0/В > 8.6, which corresponds to the conditions of minimal impact on the parameters of the sample by galvanic thermomagnetic phenomena.
 The block diagram of a device for non-contact measurement of symmetric σс and asymmetric σа components of the electrical conductivity of thermoelectric materials consists of: 1 — SV switch block; 2 — electronic switch; 3 — auto generator; 4 — AC amplifier; 5 — synchronous detector; 6 — DC amplifier; 7 — pulse generator; 8 — signal processing unit; 9 — indicator device; 10 — DC indicator; 11 — correction unit; FR1, FR2.
 Measurement of the parameters of the thermoelectric sample based on Bi-Te-Se-Sb crystals showed that the real error of the proposed method is 2 %. This indicates that the eddy current method can be successfully used to determine the main parameters of thermoelectric materials.
 The use of this method allows solving the relevant problem of avtomazation of the process of monitoring and sorting out thermoelectric ingots, billets and parts.

ВИСОКОЛІНІЙНІ БАЛАНСНІ ДВОТАКТНІ ПІДСИЛЮВАЧІ ПОСТІЙНОГО СТРУМУ ІЗ НИЗКОЮ ПОХИБКОЮ ЗСУВУ НУЛЯ

It is known that push-pull DC amplifiers (PPDA), as a rule, have a high linearity of the transfer characteristic, a wide passband (hundreds of MHz and GHz units) at the level of unity gain, and a significant rate of change in the output voltage (at least thousands of volts per microsecond). Serial models of such integrated PPDA are produced by Analog Devices, Texas Instruments, Linear Technology, National Semiconductor and others. Due to the presence of these characteristics, PPDA are widely used in current-voltage, current-current, ADC, DAC, direct digital synthesis systems and multi-channel digital systems for processing and recording analog signals. Despite the high indicated static and dynamic characteristics of the PPDAs built on bipolar transistors, which have a significant additive error in the form of an input zero bias current of hundreds of nA and μA units. Often this can degrade the static parameters of these devices and systems. When the input zero bias current appears, there are basic currents of bipolar transistors in the input stages of the amplifiers. To reduce their influence in single-cycle current amplifiers, some special circuit methods are used. Which allow an order of magnitude to reduce the input zero bias current of the differential stage without affecting the bias voltage or speed. To reduce the input zero bias current in the PPDA, it was proposed to apply basic current compensation in the input stages, as well as to build the input stages on Shiklai composite transistors, which will significantly improve the accuracy of the circuit as a whole.

Статичні й динамічні характеристики перетворювачів струм-струм на базі двотактних підсилювачів струму

In some cases, current amplifiers have an advantage over voltage amplifiers. This is due to the fact that a significant part of the parasitic parameters of integrated circuits are capacitances. In this case, it is necessary to take into account the fact that, according to the laws of switching, the voltage across the capacitor cannot change abruptly, while the current through the capacitor can change abruptly. Thus, when designing electronic circuits for various analog-digital and digital-analog accessories and systems, one should be guided by the principle of current amplification. For this, it is advisable to use converters — current-current amplifiers (CCA). Functional and schematic diagrams of a current-to-current converter with a grounded load with variable transmission coefficients based on a push-pull DC amplifier, the complexity of which is less known, are considered. The linearity errors and zero bias currents of the PPDA are estimated depending on the value of the transmission coefficients of a particular. It showed that the linearity errors do not exceed 0,001 %, and the bias current does not exceed 0,5 μA. This makes it possible to use these devices in high-frequency electronic systems and devices. The optimal values of the tuning resistor are determined, at which the linearity errors at the given transmission ratios are minimal. The dynamic characteristics of the PPDA are analyzed using the frequency response, phase response and transient response for the given current transfer coefficients. It is proved that the bandwidth is as wide as possible and is determined by the limiting frequency of the transistor amplification.

Low Noise Programmable DC Amplifier with Remote Control

Introduction. In modern experimental technology, the direction associated with the development of information-measuring systems for recording, pre-processing and analyzing excess low-frequency noise (flicker noise) is well known. Currently, such measuring systems are mainly presented in the form of particular solutions, due to the large variety of research goals and objectives. At the same time, for automation of the experiment, multichannel measuring complexes with the possibility of flexible reconfiguration of the measuring channel according to the task are highly demanded. It is obvious that any distributed measuring channel is represented as a multi-stage scheme with given functions and parameters of each stage, which makes it difficult for the measuring system to adapt to different conditions and tasks of the experiment. The logical solution to this problem is a deep unification of all components of the measuring channel while maintaining good performance characteristics. One of the main problems with this is the evaluation of the intrinsic noise of electronic elements, which provide for changing the parameters of the amplifier.Objective. Experimental analysis of the intrinsic noise of electronic potentiometers, development of the concept and study of parameters of a low-noise DC amplifier with a high degree of unification, the possibility of external electronic control and the use of built-in characteristics correction algorithms.Materials and methods. To achieve the set result, a method for measuring the noise of electronic potentiometers was proposed and experimental studies were carried out.Results. According to the calculation results and experimental studies, it was shown that the specific noise of the electronic potentiometers corresponds to the noise of the metal-film resistors, which makes it possible to use them in low-noise amplification stages. The developed circuit solutions allow the implementation of a unified amplifying module with cascading to build low-noise measuring DC paths based on electronic potentiometers. External and internal digital control allows you to significantly improve the performance of the measuring path as a whole and allows you to adapt it to a wide range of tasks.Conclusion. As part of the study, a method was proposed for measuring the noise of electronic potentiometers, analytical and experimental studies were carried out, and a prototype of a low-noise amplifier was developed and investigated.

Extraction of Eye Movements for a Communication System by EOG Signal Using DC Amplifier

Extraction of Eye Movements for a Communication System by EOG Signal Using DC Amplifier

High Accuracy and Simultaneous Scanning AC Measurement Approach for Two-Dimensional Resistive Sensor Arrays

Zero potential circuit (ZPC) is widely implemented for two-dimensional resistive sensor array/matrix measurement to eliminate the crosstalk effect caused by the additional current paths through the un-targeted sensors. However, the measurement accuracy of the ZPC method is strongly influenced by its applied multiplexer switch-on resistors and operational amplifier DC offset voltage. This paper proposes to supply simultaneously each row of the sensor matrix with an AC voltage at a row-specific frequency, so that the responses of sensors in one column can be isolated from each other based on a frequency spectrum analysis and all sensors can be therefore scanned simultaneously. Comparing to the original ZPC method, this new approach does not need the un-targeted sensors to be short-circuited, as well as the multiplexer can be omitted. The resistance value of each sensor is calculated by evaluating its column output signal at the frequency of its corresponding row excitation AC voltage source. The DC offset voltage of the operational amplifier does not influence the measurement anymore because of the AC measurement principle.

Simple thermal control of dc low-current amplifiers improves stability

Measurement of direct currents below the nA range are common in nanoscience experiments. Gain and offset thermal drifts of high-gain (G to T) transresistance amplifiers limit the measurement sensitivity and accuracy. Here we describe a simple and inexpensive thermostat, constructed from off-the-shelf consumer components, and quantify the improvements in the gain and offset stability of a commercial transresistance amplifier (FEMTO mod. DDPCA-300), popular in nanoscience experiments.

Відбивачі струму з високим і надвисоким вихідним опором на біполярних транзисторах

Current reflectors (DCs) or current mirrors built on bipolar transistors are widely used in a variety of electronic circuits, such as: DC amplifiers, code-current converters, analog-to-digital converters, power supplies, and others. The feature of low-power bipolar transistors is the ability to function in linear mode at relatively low operating voltages on collector-emitter transitions and emitter bases about 0,7…0,8 V at currents 0,1…10 mA. A new approach to the construction of an aircraft with high and ultrahigh rhythms is proposed, consisting in the use of the n-p-n and p-n-p composite transistors and allows to compensate for the change of the base current of the transistor of the regulator, which arises as a result of various factors. The static characteristics of circuits of known aircraft are analyzed, their deficiencies are determined and ways of their elimination are considered. An analytical correlation is derived for determining the initial resistances of the proposed schemes of the Sun, in particular, such that the introduction of a positive feedback in the collector circuit of the transistor of the regulator is used. A computer simulation of static characteristics was performed to determine the adequacy of the mathematical models obtained by comparing the obtained results. In addition, the construction of the aircraft with high and ultrahigh-speed rms used to construct analog signal converters is considered. The schemes of known aircraft (Vidar and Wilsono) are considered and the shortcomings of such schemes are identified. The analytical co-relation for calculation of initial impedance is deduced. Also, expressions for the coefficients of current and voltage are given, and dependencies are presented that demonstrate the work of the proposed reflectors of current at different displacement currents. A schematic design of the above-mentioned aircraft with high and ultrahigh rms, constructed using the composition of integral transistors n-p-n and p-n-p conductivity, was carried out. The recommendations for the construction of the aircraft with high and ultrahigh rms are given, which makes it possible to use them in multichannel analog-to-digital converters. A comparative analysis of some variants of the implementation of the aircraft with high and ultrahigh rye is made.