Bipolar Current Source Research Articles

A Bi-polar Current Source with High Short-term Stability for Tsinghua Tabletop Kibble Balance

A Bi-polar Current Source with High Short-term Stability for Tsinghua Tabletop Kibble Balance

A 20 A bipolar current source with 140 μA noise over 100 kHz bandwidth

The precise control of direct current (dc) magnetic fields is crucial in a wide range of experimental platforms, from ultracold quantum gases and nuclear magnetic resonance to precision measurements. In each of these cases, the Zeeman effect causes quantum states to shift in energy as a function of the magnetic field. The development of low-noise current sources is essential because electromagnets are the preferred tool to dynamically control the magnetic field. Here, we describe an ultra-low noise bipolar current source using pairs of complementary n- and p-channel metal–oxide–semiconductor field-effect transistors controlled by zero-drift operational amplifiers. Our source has a 90 kHz inherent bandwidth and provides current from −20 to 20 A with noise (0.1 Hz to 100 kHz) of 140 µA at ±20 A.

Ultra-low noise bipolar current source for ultracold atom magnetic system.

We report the development of an ultralow-noise bipolar current source based on the configuration of H-bridge current switching. The measured relative current noise fluctuation reaches 4 × 10-9Hz-1/2, which enables an ultra-stable magnetic system for cold atom experiments. We avoid the influence of the AC leakage currents induced by the large parasitic capacitance of the H-bridge. First, the current sensor is placed as close as possible to the magnetic coils so that the systematic errors from these leakage currents are minimized. Second, the large parasitic capacitance, which parallels the magnetic coils and forms an LC oscillator, is removed from the feedback loop in our setup to maintain a large self-resonance frequency of the feedback control loop. These two improvements lead to a current source that is more precise and less noisy. Remarkably, the lowest current noise density produced by the proposed method is only 500 nA Hz-1/2 at a current of 100A, which is about ten fold smaller than the case with leakage current. To optimize the feedback control, a numerical simulation is implemented by using Matlab Simulink, and the numerical simulation results are entirely consistent with the experimental results.

A High Dynamic Range and Ultralow-Noise Bipolar Current Source for Unshielded SERF Atomic Magnetometers

A High Dynamic Range and Ultralow-Noise Bipolar Current Source for Unshielded SERF Atomic Magnetometers

A High-Speed Protection Strategy for Bipolar CSC-Based HVDC Transmission System

This paper introduces a novel approach to high-speed fault protection strategy for bipolar Current Source Converter (CSC) based high voltage DC transmission line. The Bagged-Tree Ensemble-Classifier (BTEC) method is employed to detect the presence of a fault and categorizes the various types of faults in the DC transmission line. The implementation of the Wavelet Transform (WT) technique assists in diminishing the effect of deviation in the fault resistance value, fault location, and disturbances created due to noise on the performance BTEC method. The development of the predictive model through concatenating individual models is the prime objective of the ensemble schemes. Ensemble procedure assists to enhance the performance accuracy of the fault protection strategy. The local measurement at the rectifier end side is enough for the proposed strategy to realize the protection of the entire line with no use of communication channels. The AC sinusoidal voltage, DC current and DC voltage are recorded at the rectifier end terminal and sampled at 1 kHz, which is very less as compared to the other existing techniques. The proposed strategy detects the fault in the least possible time of 4 ms and able to classify all the tested faults with reasonable accuracy. The results convey that the proposed strategy offers high-speed detection of fault and preciseness in the classification of all types of faults, despite variation in the fault resistance up to 180 Ω. The proposed scheme is applicable for DC faults and also detects the presence of AC faults in either rectifier end as reverse fault and in inverter end as sub-sequent forward section fault.

Analysis of Bipolar Integrated Circuit Degradation Mechanisms Against Combined TID–DD Effects

Integrated circuits sensitive to both total ionizing dose (TID) and displacement damage (DD) effects can exhibit degradation profiles resulting from a combination of degradation mechanisms induced by both effects. This work presents circuit simulations based on experimental data to explain degradation mechanisms induced by combined TID and DD effects on a bipolar IC current source. First, the effect of the degradation of each internal transistor on the circuit's response is evaluated by applying electrical parametric changes. Then simulations are performed from different degradation scenarios based on observed circuit behaviors to reproduce the different TID, DD, and combined TID-DD responses. These simulations show that a synergistic interaction between a current leakage induced by DD on a transistor located in the bandgap reference part with the gain degradation of a current mirror induced by both TID and DD appears to be responsible for the combined TID-DD response. It is also shown that the circuit degradation rate depends on the DDD/TID rate ratios encountered during the exposition.

Dual feedback based bipolar current source with high stability for driving voice coil motors in wide temperature ranges

Bipolar current sources with a stability better than 0.1% in the temperature range of -30 to +70 °C are demanded for driving voice coil motors applied in a new ultra-quiet satellite platform, but almost none of the existing designs satisfy the harsh requirements. This paper presents a possible solution, which is essentially a floating-load, bipolar current source circuit with a dual feedback path. The key circuit is a composite amplifier (co-amp) composed of a high precision amplifier for error correction and a high power amplifier for load driving. The first feedback path comprises a specially designed four-wire current-sense resistor for current-to-voltage conversion and a discrete instrumentation amplifier for amplifying the converted voltage and closing the loop. The second feedback path is a proposed compensation network for loop stability. Error budgets for evaluating current stability and choosing key components of the circuit are comprehensively studied based on a derived rigorous current equation. Loop-stability problems attributable to the inductive load and the high open-loop gain of the co-amp are analyzed, and the proposed dual feedback compensation method is verified by theory, simulation, and measurement. All these contributions are demonstrated by three implemented prototypes with an output of up to ±2A. The measured results agree well with theoretical predictions. The best and the worst stability performances of the three prototypes at +2 and -2A are, respectively, 394 and 986 ppm in the temperature range of -30 to +70 °C, which are close to the theoretical value of 776 ppm.

MEDUSA: A Low-Cost, 16-Channel Neuromodulation Platform with Arbitrary Waveform Generation

Neural stimulation systems are used to modulate electrically excitable tissue to interrogate neural circuit function or provide therapeutic benefit. Conventional stimulation systems are expensive and limited in functionality to standard stimulation waveforms, and they are bad for high frequency stimulation. We present MEDUSA, a system that enables new research applications that can leverage multi-channel, arbitrary stimulation waveforms. MEDUSA is low cost and uses commercially available components for widespread adoption. MEDUSA is comprised of a PC interface, an FPGA for precise timing control, and eight bipolar current sources that can each address up to 16 electrodes. The current sources have a resolution of 15.3 nA and can provide ±5 mA with ±5 V compliance. We demonstrate charge-balancing techniques in vitro using a custom microelectrode. An in vivo strength-duration curve for earthworm nerve activation is also constructed using MEDUSA. MEDUSA is a multi-functional neuroscience research tool for electroplating microelectrodes, performing electrical impedance spectroscopy, and examining novel neural stimulation protocols.

Ultra-low noise and high bandwidth bipolar current driver for precise magnetic field control.

Current sources with extremely low noise are significant for many branches of scientific research, such as experiments of ultra-cold atoms, superconducting quantum computing, and precision measurements. Here we construct and characterize an analog-controlled bipolar current source with high bandwidth and ultra-low noise. A precise and stable resistor is connected in series with the output for current sensing. After being amplified with an instrumentation amplifier, the current sensing signal is compared with an ultra-low noise reference, and proportional-integral (PI) calculations are performed via a zero-drift low-noise operational amplifier. The result of the PI calculation is sent to the output power operational amplifier for closed-loop control of the output current. In this way, a current of up to 16 A can be sourced to or sunk from a load with a compliance voltage of greater than ±12 V. The broadband current noise of our bipolar current source is about 0.5 μA/Hz and 1/f corner frequency is less than 1 Hz. Applications of this current source in a cold atom interferometer, as well as active compensation of a stray magnetic field, are presented. A method for measuring high-frequency current noise in a 10 A DC current with a sensitivity down to a level of 10 μA is also described.

Bipolar Steep Pulse Current Source for Highly Inductive Load

A bipolar pulse current source is proposed for a highly inductive load. The current source exploits a noninductive capacitor to store or release the energy back to and from inductive load during switching on or off of power inverter. A boost module is designed at the dc side of inverter to supplement the required energy gap so that edge steepness of the load current can be improved. The capacitor and boost elements are configured based on the analysis of capacitor impact on the load current and boost inductor current. The stability of load current can be guaranteed by the multiple driving pulses generated from closed-loop control of boost switch, regardless of load changes or initial pulse width offset. An experiment prototype is built to generate a flat-top 20 A current with the 200 μs rise/fall time for an inductive load of 2 mH or higher. Due to the steep rising and falling edges, the inductive load can realize high-frequency pulse currents. Moreover, the steep pulse current source can excite strong magnetic field, which make it especially useful for the inductive coils of high-power geophysical transient electromagnetic method (TEM) transmitter.

Bipolar square-wave current source for transient electromagnetic systems based on constant shutdown time.

Cooperative work of multiple magnetic transmitting sources is a new trend in the development of transient electromagnetic system. The key is the bipolar current waves shutdown, concurrently in the inductive load. In the past, it was difficult to use the constant clamping voltage technique to realize the synchronized shutdown of currents with different peak values. Based on clamping voltage technique, we introduce a new controlling method with constant shutdown time. We use the rising time to control shutdown time and use low voltage power source to control peak current. From the viewpoint of the circuit energy loss, by taking the high-voltage capacitor bypass resistance and the capacitor of the passive snubber circuit into account, we establish the relationship between the rising time and the shutdown time. Since the switch is not ideal, we propose a new method to test the shutdown time by the low voltage, the high voltage and the peak current. Experimental results show that adjustment of the current rising time can precisely control the value of the clamp voltage. When the rising time is fixed, the shutdown time is unchanged. The error for shutdown time deduced from the energy consumption is less than 6%. The new controlling method on current shutdown proposed in this paper can be used in the cooperative work of borehole and ground transmitting system.

Flyback Topology TEM Bipolar Pulse Transmitter

In the fields of transient electromagnetic (TEM) geophysical exploration, it is necessary to create a bipolar pulse current source with decline edge of high linearity, short turn-off time and high stability. In order to improve detection equipment’s practicality, it’s urgently needed to miniaturize and improve the reliability of the detection equipment. In this paper, a clamp and prompt drop bipolar pulse current circuit based on Flyback topology is represented, which can accelerate the decline of load current by clamping the coil load with fixed high voltage in the period of current declining. Also, because of this circuit’s low power consumption and significantly improvement of the transmitter’s energy utilization, chassis’s cooling equipment can be greatly reduced and it’s easier to miniaturize the transmitter. To start with, the principle of this circuit is represented. Then, the method is given to select the optimal values of circuit’s components. Finally, the results of simulation proves the proposed circuit meeting the requirements much better than those reported, with shorter turn-off time, higher linearity, less energy consumption. In general, this circuit has been successfully applied to a new type of detection equipment. DOI: http://dx.doi.org/10.11591/telkomnika.v11i9.3250

Constant Voltage-clamping Bipolar Pulse Current Source for Transient Electromagnetic System

This article proposes a bipolar pulse current source for the transient electromagnetic system. This current source consists of a full-bridge converter circuit, a constant voltage-clamping circuit, and a damping-snubber circuit. Bipolar pulses are generated by the full-bridge converter circuit. During the rising edge of the pulse current, the high voltage generated by the constant voltage-clamping circuit is added to the load, which will enhance the rising speed of the pulse current and help the current quickly stabilize. Similarly, for the falling edge, the constant voltage acts on the load, brings out a linear falling edge, and efficiently shortens the turn-off time. The damping snubber circuit is then used to eliminate the ringing happening in the current-reduced-to-zero vicinity. Its operation principles are described, and calculations of the main parameters are also provided. Simulation and experimental results show that the current source has a fast rising edge, a highly linear falling edge, and a short turn-off time, which helps to enhance the transmitting frequency of the current source and the efficiency of the transient electromagnetic system.

A New High Efficiency Current Source Driver With Bipolar Gate Voltage

A novel bipolar current source driver (CSD) for power MOSFETs is proposed in this paper. The proposed bipolar CSD alleviates the gate current diversion problem of the existing CSDs by clamping the gate voltage to a flexible negative value (such as -3.5 V) during turn-off transition. Therefore, the proposed driver is able to turn off the MOSFET much faster with a higher effective gate current. The idea presented in this paper can also be extended to other CSDs to further improve the efficiency with high output currents. The experimental results verify the benefits of the proposed CSD. For buck converters with 12 V input at 1 MHz switching frequency, the proposed driver improves the efficiency from 80.5% using the existing CSD to 82.5% (an improvement of 2%) at 1.2 V/30 A, and at 1.3 V/30 A output, from 82.5% using the existing CSD to 83.9% (an improvement of 1.4%).

Reconfigurable 4 × 4 Switch Matrix for Ka-Band Geo-Stationary Satellite Mission

A 4 × 4 reconfigurable switch matrix based on low temperature co-fired ceramic technology for Geo-stationary satellite mission at Ka-band downlink frequencies (17–22 GHz) is presented. In comparison to its predecessor, the new generation of switch-matrix features augmented functionality whilst an overall reduced size (40%). The distinguished characteristics include the shifting of matching networks from top-layer into the embedded layers of the multilayer ceramic stack and the elimination of two external peripherals required to digitally control the bipolar current sources of the PIN-diodes based switch integrated circuits. As an additional functionality, four passive transparent paths between corresponding input and output are integrated within the module, to exhibit rudimentary transmission through the module in case of on-board power failure.

Six-bit 2.7-GS/s 5.4-mW Nyquist complementary metal-oxide semiconductor digital-to-analogue converter for ultra-wideband transceivers

This study presents a 6-bit 2.7 GS/s low-power digital-to-analogue converter (DAC) for ultra-wideband transceivers. A ‘2(thermometer)+4(binary)’ segmented architecture is chosen to reach a compromise between the current source cell's area and the operating speed of the thermometer decoder. In addition, the proposed pseudo-thermometer structure improves the DAC's dynamic performance. The bipolar current source cell and latch clock delay technique are employed to reduce the power consumption in the analogue and digital parts, respectively. Moreover, the compact de-glitch latch presented in this study simplifies the conventional latch design and layout. This DAC was implemented in a standard 0.13 µm 1P8M complementary metal-oxide semiconductor technology with the active area of 0.0585 mm2. The measured differential non-linearity and integral non-linearity are less than 0.09 and 0.11 least significant bit, respectively. The measured spurious-free dynamic range is more than 36 dB over the Nyquist frequency at the sampling frequency of 2.7 GHz. The DAC consumes 5.4 mW with a near-Nyquist sinusoidal output at 2.7 GS/s, resulting in a better figure of merit of 31 fJ/conversion-step than other published arts.

An Area-Efficient, Low-Power CMOS Fractional Bandgap Reference

This paper proposes an area efficient, low power, fractional CMOS bandgap reference (BGR) utilizing switched-current and current-memory techniques. The proposed circuit uses only one parasitic bipolar transistor and built-in current source to generate reference voltage. Therefore significant area and power reduction is achieved, and bipolar transistor device mismatch is eliminated. In addition, output reference voltage can be set to almost any value. The proposed circuit is designed and simulated in 0.18µm CMOS process, and simulation results are presented. With a 1.6V supply, the reference produces an output of about 628.5mV, and simulated results show that the temperature coefficient of output is less than 13.8ppm/°C in the temperature range from 0°C to 100°C. The average current consumption is about 8.5µA in the above temperature range. The core circuit, including current source, opamp, current mirrors and switched capacitor filters, occupies less than 0.0064mm2 (80µm × 80µm).

Differential effects produced by ketamine on oscillatory activity recorded in the rat hippocampus, dorsal striatum and nucleus accumbens

Previously, we showed that NMDA antagonists enhance high-frequency oscillations (130-180 Hz) in the nucleus accumbens. However, whether NMDA antagonists can enhance high-frequency oscillations in other brain regions remains unclear. Here, we used monopolar, bipolar and inverse current source density techniques to examine oscillatory activity in the hippocampus, a region known to generate spontaneous ripples (∼200 Hz), its surrounding tissue, and the dorsal striatum, neuroanatomically related to the nucleus accumbens. In monopolar recordings, ketamine-induced increases in the power of high-frequency oscillations were detected in all structures, although the power was always substantially larger in the nucleus accumbens. In bipolar recordings, considered to remove common-mode input, high-frequency oscillations associated with ketamine injection were not present in the regions we investigated outside the nucleus accumbens. In line with this, inverse current source density showed the greatest changes in current to occur in the vicinity of the nucleus accumbens and a monopolar structure of the generator. We found little spatial localisation of ketamine high-frequency oscillations in other areas. In contrast, sharp-wave ripples, which were well localized to the hippocampus, occurred less frequently after ketamine. Notably, we also found ketamine produced small, but significant, changes in the power of 30-90 Hz gamma oscillations (an increase in the hippocampus and a decrease in the nucleus accumbens).

Wide Band Howland Bipolar Current Source using AGC Amplifier

Electrical impedance tomography (EIT) is a promising technique for imaging the conductivity distribution within the body from voltage surface measurements. The measuring precision is very important, where inaccuracies from the current source generate distortions in the images. These are particularly caused by stray capacitances which reduce the frequency response of the instrumentation. This paper investigates the performance of a bipolar current source attached to a multiplexer using an Automatic Gain Control (AGC) Amplifier circuit. Output current measurements were made in the frequency range 100 Hz to 1 MHz and also output impedance at 100 kHz, both with and without the AGC Amplifier circuit. The results showed a constant output current with a maximum error of ±2% when using the AGC Amplifier circuit whereas 300% not using it. Also, the output impedance was approximately 10.4 and 1.2 M? with and without using the AGC Amplifier circuit, respectively. It can be concluded that the AGC Amplifier circuit may increase significantly the precision of the current measurements and may improve the image quality in EIT systems.

Hardware and Software of a Bipolar Current Source Controlled by PC.

This paper describes a realization of a bipolar current source developed by the paper's authors. The source is intended for use in galvanic and other industrial plants, where a pulse-reverse current supply (with the desired shape in time) is required. A prototype of the device, which provides the outcome current intensity up to ± 50 A, has been constructed. The hardware of the source consists of a Pentium IV PC, a commercial ADDA converter, an interface of authors' original construction as well as a current regulator. The application software is developed using a commercial packet LabView as the basis.