Built-in Resistors Research Articles

Linear Synaptic Weight Update in Selector-Less HfO₂ RRAM Using Al₂O₃ Built-In Resistor for Neuromorphic Computing Systems

Linear Synaptic Weight Update in Selector-Less HfO₂ RRAM Using Al₂O₃ Built-In Resistor for Neuromorphic Computing Systems

New Normal Mode dv/dt Filter With a Built-In Resistor Failure Detection Circuit

Insulated gate bipolar transistors (IGBTs) will soon be replaced by wide band gap devices (SiC and GaN) as the choice for power semiconductor switch in voltage source inverters. These devices have extremely fast rise time and fall time compared with IGBT devices. The high dv/dt of pulse-width modulation outputs create excessive voltage stress in the insulation system of ac motors due to voltage reflection issues associated with motors at large distances from the drive. In many oil field applications, the distance between the motor and the variable frequency drive approaches 300 m. In walking rig applications, it is common to use multiple smaller sized conductors per phase, bunched together, to achieve the desired ampacity. This practice results in higher than usual value of the cable parasitic capacitance. Traditional dv/dt filters used for mitigating over-voltage at motor terminals have been found to be inadequate in reducing the over voltage at the motor terminals in such oil field installations. The damping resistor often experiences high voltage and gets damaged. A new dv/dt filter suitable for use with high power ac motors at distances nearing 300 m with a built-in resistor failure detection circuit is proposed here. Test results are given to demonstrate its efficacy.

Adjustable built-in resistor on oxygen-vacancy-rich electrode-capped resistance random access memory

In this study, an adjustable built-in resistor was observed on an indium–tin oxide (ITO)-capped resistance random access memory (RRAM) device, which has the potential to reduce operating power. Quite notably, the high-resistance state (HRS) current of the device decreased with decreasing current compliance, and a special situation, that is, a gradual change in current always appears and climbs slowly to reach the compliance current in the set process even when the compliance current decreases, was observed. Owing to this observed phenomenon, the device is regarded to be equipped with an adjustable built-in resistor, which has the potential for low-power device application.

Electrical safety of commercial Li-ion cells based on NMC and NCA technology compared to LFP technology

Since a laptop caught fire in 2006 at the latest, Li-ion cells were considered as more dangerous than other accumulators [1]. Recent incidents, such as the one involving a BYD e6 electric taxi [2] or the Boeing Dreamliner [3], give rise to questions concerning the safety of L#i-ion cells. This is a crucial point, since Li-ion cells are increasingly integrated in all kinds of (electric) vehicles. Therefore the economic success of hybrid electric vehicles (HEV) and battery electric vehicles (BEV) depends significantly on the safety of Li-ion cells. Lithium nickel manganese cobalt oxide (NMC) and lithium nickel cobalt aluminium oxide (NCA) are two standard Li-ion cathode chemistries, which are often used for today’s HEVs and BEVs Li-ion batteries. Cells with this two cathode technologies are investigated in detail and compared to cells with the alleged save lithium iron phosphate (LFP) technology. Furthermore only commercially available and mass produced Li-ion cells were tested, in order to get as close to real end-user applications as possible. To ensure comparability, cells with the most common 18650 casing have been used. Furthermore all cells had no built-in resistor with positive temperature coefficient (PTC-device). For each abuse test at least 2 cells have been tested to get to know the statistical dispersion. The spread was in all tests for all measured values of each cell type lower than 11 %. Consequently it can be supposed, that mass produced cells show equal behaviour also in abusive test. The performed electrical safety tests on these cells, involve overcharge, overdischarge and short circuit tests. These tests represent real abuse scenarios and are geared to established standards [15], [16], [17], [18]. To complete these measurements an accelerated rate calorimetry (ARC) test has been carried out, to determine the thermal stability of the cells. As in the literature discussed, the investigated LFP/C cells show a higher thermal stability and are therefore safer, although they do not have any overcharge buffer as the investigated NCA/C and NMC/C cells.

Design and fabrication of novel three-dimensional multi-electrode array using SOI wafer

A novel method has been developed for the manufacture of a three-dimensional multi-electrode array (3D MEA), particularly, the shape of micro-tips can be varied by MEMS technology to construct different multi-electrode array. It improved the disadvantage of single electrode, which meant that it was available for multi-recording and analysis of a series of signals. Overcoming the difficulty of making interconnection line on 3D MEA chips via innovative fabrication process design. Using local isolation and removal of oxide films to forming electrodes and interconnections with oxide isolation covers. A 10 × 10 3D MEA with a distance of 100 μm between each other for further bio-neural signals was demonstrated, and a test on rabbit retina was also available. Besides, integrating pre-amplifier and built-in resistors with 3D MEA was brought out to hopefully increase the efficiency of sensing.

Varistors based on mixed-phase ceramics containing ZnO and negative temperature coefficient spinels

High nonlinearity coefficients of 60–150 are observed in the current-voltage (I-V) curves of the mixed phase ceramics formed by cosintering ZnO with spinel phases having large negative temperature coefficients (NTCs) in resistivity. The region of negative slope in the I-V curves of the NTC ceramics is progressively made positive with ZnO phase content, wherein ZnO grains function as a built-in resistor in series to the resistance of the NTC phase. High α depends on the optimum phase content of ZnO as much as its intrinsic conductivity. The studies indicate that the predominent contribution to power dissipation is by way of joule heating from the resistive component of the current.

High dI/dT light-triggered thyristors

Directly light-triggered, 4000- and 6000-V thyristors were designed, fabricated, and tested to obtain high performance in dI/dt, dV/dt, and photosensitivity. Built-in resistors protected both auxiliary stages during high dI/dt turn-on. The novel use of etched moats to define the resistors was compatible with an optical gate structure that gives high dV/dt and good photosensitivity. No additional processing steps were needed to fabricate these devices, as compared to standard light-triggered thyristors. A record value of 1000 A/µs at 60 Hz was measured on a 6000-V thyristor, and 850 A/µs was safely triggered with only 1.8 mW of light. The dV/dt immunity of the photogate structure measured 4000 V/µs, rising exponentially to 80 percent of 4000 V, V <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">DRM</inf> . Thyristors triggered by dV/dt were not destroyed. A new model of resistor heating was combined with the first measurements of the current pulses through both built-in resistors to identify the mechanism responsible for occasional burn-out of the second resistor. The failure mechanism was conductivity modulation in the surface of the resistor during its microsecond on-time caused by thermally generated carriers. The test results confirmed the utility of built-in resistors for high dI/dt performance with minimal light power and for nondestructive dV/dt triggering.