The Kynix Blog

cientists have created a material that could make reading biological signals, from heartbeats to brainwaves, much more sensitive. Organic electrochemical transistors (OECTs) are designed to measure signals created by electrical impulses in the body, such as heartbeats or brainwaves. However, they are currently only able to measure certain signals.Now researchers led by a team from Imperial College London have created a material that measures signals in a different way to traditional OECTs that they believe could be used in complementary circuits, paving the way for new biological sensor technologies.Semiconducting materials can conduct electronic signals, carried by either electrons or their positively charged counterparts, called holes. Holes in this sense are the absence of electrons - the spaces within atoms that can be filled by them.Electrons can be passed between atoms but so can holes. Materials that use primarily hole-driven transport are called 'p-type' materials, and those that use primarily electron-driven transport are called, and 'n-type' materials.An 'ambipolar' material is the combination of both types, allowing the transport of holes and electrons within the same material, leading to potentially more sensitive devices. However, it has not previously been possible to create ambipolar materials that work in the body.The current most sensitive OECTs use a material where only holes are transported. Electron transport in these devices however has not been possible, since n-type materials readily break down in water-based environments like the human body.But in research published today in Nature Communications, the team have demonstrated the first ambipolar OECT that can conduct electrons as well as holes with high stability in water-based solutions.The team overcame the seemingly inherent instability of n-type materials in water by designing new structures that prevent electrons from engaging in side-reactions, which would otherwise degrade the device.These new devices can detect positively charged sodium and potassium ions, important for neuron activities in the body, particularly in the brain. In the future, the team hope to be able to create materials tuned to detect particular ions, allowing ion-specific signals to be detected.Lead author Alexander Giovannitti, a PhD student under the supervision of Professor Iain McCulloch, from the Department of Chemistry and Centre for Plastic Electronics at Imperial said:"Proving that an n-type organic electrochemical transistor can operate in water paves the way for new sensor electronics with improved sensitivity. "It will also allow new applications, particularly in the sensing of biologically important positive ions, which are not feasible with current devices. For example, these materials might be able to detect abnormalities in sodium and potassium ion concentrations in the brain, responsible for neuron diseases such as epilepsy." Reference:2N3811DMA204020RDMMT5551S-7-F 

Omron Electronic Components Europe is launching a new dust sensor module, offering four times greater sensitivity compared with other LED dust sensors on the market. The higher performance and greater sensitivity of the sensor will allow tighter pollution control as well as the creation of more effective air purifiers and similar systems. Omron’s Dust Sensor is able to detect particles as small as 1 micron, less than half the size of the PM2.5 standard for fine particulate matter in the atmosphere.It also features a high air throughput, of around 6 times that of established alternatives, giving improved sensitivity of response to changes in the environment.Commenting, Gabriele Fulco, European Product Marketing Manager Sensors, Omron said “Controlling air pollution including emissions from vehicles as well as cigarette and other smoke is a major concern for city authorities and building managers alike"."It is only possible to control what can be detected, so Omron believes it is making a major contribution to the environment and public health by launching this new, highly sensitive dust sensor.”The new Omron dust sensor is highly compact, sized just 50mm x 45mm x 20mm – giving it an overall size of 20% less than popular alternative solutions. The sensor is part of a growing range of Omron solutions for HVAC and other environmental systems.They include the D6F-PH MEMS pressure sensor and the velocity sensors D6F-V which incorporate a Dust segregation System (DSS). The design of all Omron sensors guarantees very sensitive and temperature compensated measurement of air for a precise HVAC control.Reference:GP2Y1+GP2Y1010AU0FDN7C3CA006SM-PWM-01C

By combining 3D holographic lithography and 2D photolithography, researchers from the University of Illinois at Urbana-Champaign have demonstrated a high-performance 3D microbattery suitable for large-scale on-chip integration with microelectronic devices."This 3D microbattery has exceptional performance and scalability, and we think it will be of importance for many applications," explained Paul Braun, a professor of materials science and engineering at Illinois. "Micro-scale devices typically utilize power supplied off-chip because of difficulties in miniaturizing energy storage technologies. A miniaturized high-energy and high-power on-chip battery would be highly desirable for applications including autonomous microscale actuators, distributed wireless sensors and transmitters, monitors, and portable and implantable medical devices.""Due to the complexity of 3D electrodes, it is generally difficult to realize such batteries, let alone the possibility of on-chip integration and scaling. In this project, we developed an effective method to make high-performance 3D lithium-ion microbatteries using processes that are highly compatible with the fabrication of microelectronics," stated Hailong Ning, a graduate student in the Department of Materials Science and Engineering and first author of the article, "Holographic Patterning of High Performance on-chip 3D Lithium-ion Microbatteries," appearing in Proceedings of the National Academy of Sciences."We utilized 3D holographic lithography to define the interior structure of electrodes and 2D photolithography to create the desired electrode shape." Ning added. "This work merges important concepts in fabrication, characterization, and modeling, showing that the energy and power of the microbattery are strongly related to the structural parameters of the electrodes such as size, shape, surface area, porosity, and tortuosity. A significant strength of this new method is that these parameters can be easily controlled during lithography steps, which offers unique flexibility for designing next-generation on-chip energy storage devices."Enabled by a 3D holographic patterning technique—where multiple optical beams interfere inside the photoresist creating a desirable 3D structure—the battery possesses well-defined, periodically structured porous electrodes, that facilitates the fast transports of electrons and ions inside the battery, offering supercapacitor-like power."Although accurate control on the interfering optical beams is required to construct 3D holographic lithography, recent advances have significantly simplified the required optics, enabling creation of structures via a single incident beam and standard photoresist processing. This makes it highly scalable and compatible with microfabrication," stated John Rogers, a professor of materials science and engineering, who has worked with Braun and his team to develop the technology."Micro-engineered battery architectures, combined with high energy material such as tin, offer exciting new battery features including high energy capacity and good cycle lives, which provide the ability to power practical devices," stated William King, a professor of mechanical science and engineering, who is a co-author of this work.   

Overview: The article discusses the SC robustness, surge energy, and overvoltage robustness of GaN HEMTs. Additionally, the article highlights recent achievements in ultrafast SC protection circuits and alternative circuit approaches. For many applications, including motor drives, automobile powertrains, and electric grids, the ability of power devices to stand up to overvoltage, overcurrent, and surge-energy events is a crucial need for robustness. For Si and SiC power transistors, UIS (avalanche) and SC tests are typically used to measure robustness.  Does gallium nitride possess SC robustness? It is known that GaN HEMTs lack avalanche capabilities and have restricted SC robustness. Furthermore, compared to Si and SiC devices, GaN HEMTs behave considerably differently in terms of stress tolerance and failure under specific out-of-safe-operating area situations.  The SC robustness, surge energy, and overvoltage robustness of GaN HEMTs will be discussed. Fig. 1 shows an illustration of GaN SP-HEMT and GaN HD-GIT.Fig. 1. Illustration of (a) GaN SP-HEMT and (b) GaN HD-GIT. Source: IEEE Transactions on Power Electronics SC Robustness When there is a conduction path with minimum resistance between the power source and the switching transistor, SC fault occurrences take place. SC events typically drive devices into saturation mode, which stresses the device with high voltage and high conduction current. Objectives Standard SC robustness criteria are:10 μs SC withstanding time (tSC) under the bus voltage (VBUS) The driving conditions must be identical to the application-use operation.Note: The U.S. Department of Energy 2025 Vehicle Drive Roadmap states that a 2 μs tSC of the power device along with the ultrafast protection circuit is required if the 10 μs tSC is not achievable. Types of SC Robustness In power electronics systems, there are typically four types of SC situations that can occur: Arm SC, also known as the hard-switching fault (HSF) or SC type ISeries arm SCOutput SCGround SCHSF is typically used in these situations to assess the robustness of the SC power device. The findings of repeated SC tests, failure modes, and single-event tSC for GaN HEMTs are compiled in this section. Reasons for Restricted SC in GaN HEMT A lot of work has been done to figure out what limits the SC capability of GaN HEMTs, especially when the bus voltage is high. Devices fail thermally in long SC duration tests with low bus voltage. At high bus voltages, several reports point to an electrical failure.  It is suggested that the high electric field produced by the hole accumulation beneath the gate—where the holes are produced by impact ionization—may be the reason for the SC failure. The relationship between electric field crowding at the drain-side gate edge and the high carrier density caused by the SC has been reported. A wafer-level transient voltage measurement keeps track of the potential profile in the gate-drain region under SC stress.  It is found that the failure is dependent on the speed at which the electric field propagates; impact ionization causes the failure when a high electric field reaches the drain edge. Results of Repetitive SC stresses on GaN HEMTs It has been documented that GaN HEMTs are not sufficiently robust to repetitive SC stresses within the single-event SC SOA. In SP-HEMTs, the repetitive SC stresses cause a decrease in drain-leakage currents and a rise in on-resistance (RDS,ON) at lower bus voltages. All of these parametric shifts point to the possibility of electron trapping during the repetitive SC operation in the buffer and gate areas. In HD-GIT repetitive SC tests, the progression of developing cracks and aluminum extrusion at this load has been seen.In cascode HEMT, two additional strategies have been identified to constrain the SC robustness The first thing that can happen is that the parasitics of the Si-GaN chip interconnection can cause the self-sustained gate oscillation to excite. This can make the GaN HEMT turn on by accident and fail. Secondly, the cascode HEMT's thermal self-regulation capability on the gate control is lower than that of HD-GITs and SP-HEMTsMethods to Overcome SC Faults Protection circuits must be included for applications where the SC fault may arise due to the short SC withstanding time of contemporary GaN HEMTs. Within 100–200 ns, the protection circuit should identify the issue and clear it. Conventional desaturation circuits have a long response time, which makes it difficult to achieve this. Ultrafast SC protection circuits for GaN HEMTs have recently been achieved by several groups. These circuits typically exhibit fault detection and clearance times of less than 100 ns. Some other good qualities that have been talked about are strong dv/dt noise immunity, use with parallel-connected GaN HEMTs, and monolithic integration with the GaN device. Alternative circuit approaches to improve the SC capability in addition to quick protection are also suggested, such as coupling the GaN HEMT to a Si mosfet.Device-level enhancements have also been reported to enhance the SC withstanding time of GaN devices, in addition to circuit techniques. Removing parts of the 2DEG channel along the width of the GaN HEMT is an easy way to minimize the saturation current. With this method, an SC withstanding time over 3 μs is possible in industrial cascode GaN HEMTs. Surge Energy Power devices would greatly benefit from the ruggedness against surge energy in addition to SC robustness. Si/SiC MOSFETs and IGBTs have relied on their avalanche ability—an impact ionization and multiplication effect—to support high current at high drain-to-source bias. Why is surge energy important for power devices? When devices are exposed to surge energy, drain-to-source bias quickly climbs to and clamps at avalanche breakdown voltage. Avalanching in the device causes the drain current to decrease to zero and the surge energy to be resistively dissipated. The dissipation of energy stops converters from circulating energy further. For this reason, avalanche ruggedness is another name for surge-energy ruggedness. An essential indicator of device robustness is avalanche energy, which is the maximum energy that a power device can dissipate without causing a thermal runway. Surge Energy in GaN HEMTS However, the intrinsic avalanche capacity is absent from GaN HEMTs. The JEDEC JC 70 committee has just identified their surge-energy robustness as a crucial evaluation problem. GaN HEMTs show a quick rise in drain-to-source bias when they are exposed to surge energy. This is because of the resonance between output capacitance and parasitic inductance in the circuit.  This standing process cannot release energy until the resonance voltage drops, which causes the GaN HEMTs to turn on in reverse. The device's overvoltage margin is the principal cause of electrical failure in the withstand process.  The convergence of overvoltage and surge-energy robustness for GaN HEMTs is demonstrated in the discussion above. GaN HEMTs can generally tolerate higher surge energies at the expense of slower switching speed when they are constructed with a larger output capacitance and a higher dynamic breakdown voltage. Any nonavalanche power device can be designed or chosen with this tradeoff in mind for a variety of applications. Summarizing the Key PointsUIS (avalanche) and SC tests are typically used to measure the robustness of Si and SiC power transistors. GaN HEMTs lack avalanche capabilities and have restricted SC robustness compared to Si and SiC devices. Standard SC robustness criteria include 10 μs SC withstanding time under the bus voltage and identical driving conditions to the application-use operation. Recent achievements in ultrafast SC protection circuits for GaN HEMTs and alternative circuit approaches have improved SC capability. And, device-level enhancements have been reported to enhance the SC withstand time of GaN devices.Surge energy, which is the maximum energy that a power device can dissipate without causing a thermal runway, is also important for power devices in addition to SC robustness since it is an essential indicator of device robustness.GaN HEMTs can generally tolerate higher surge energies at the expense of slower switching speed when they are constructed with a larger output capacitance and a higher dynamic breakdown voltage.ReferenceKozak, Joseph Peter, Ruizhe Zhang, Matthew Porter, Qihao Song, Jingcun Liu, Bixuan Wang, Rudy Wang, Wataru Saito, and Yuhao Zhang. “Stability, Reliability, and Robustness of GaN Power Devices: A Review.” IEEE Transactions on Power Electronics 38, no. 7 (July 2023): 8442–71. https://doi.org/10.1109/tpel.2023.3266365.

Overview: The article discusses the vital role of feedback amplifiers in electronic circuits and examines their types. It also highlights the desirable effects of negative feedback on signal amplification, enhancing overall performance. To improve the reliability and performance of amplification circuits, feedback amplifiers play an essential role in electronics. A feedback loop allows these amplifiers to fine-tune and enhance their output, leading to more accurate and dependable operation. What is feedback?The term "feedback" describes the process of redirecting a portion of an amplifier's output signal into an input signal. Here, the input to the circuit is a portion of the output signal that has been added or reduced to the source signal. Consequently, the amount of feedback may rise or fall based on the operation of adding or subtracting the signal from the source signal. What is a feedback amplifier?An important part of the amplifier is the feedback circuit, which works by feeding back some of the signal's output to the input. These amplifiers have several uses since they provide better control over many parameters.Types of FeedbackPositive FeedbackPositive feedback occurs when feedback is used to increase the input signal. Positive feedback adds to the input signal, and the new input to the circuit is greater than the source signal. For this reason, it is also known as regenerative feedback. Positive feedback occurs when the feedback energy (voltage or current) is in phase with the input signal. Fig. 1 shows that both the amplifier and the feedback network create a 180° phase shift. As a result, the sum of the 360° phase shift around the loop occurs, and the feedback voltage (Vf) becomes in phase with the input signal (Vin). Fig. 1 Illustration of the positive feedback amplifier. Source: Rakesh Kumar, Ph.D.The positive feedback increases the amplifier's gain. However, it has the drawbacks of increased distortion and instability. Positive feedback is, therefore, rarely used in amplifiers. Positive feedback is utilized in oscillators, multivibrator circuits, and some active filters. Negative FeedbackNegative feedback is defined as feedback that decreases the input signal. Degenerative feedback, also known as negative feedback, occurs when the signal feedback is out of phase with the input signal by 180°. Negative feedback occurs when the input signal's voltage or current is out of phase with the feedback energy. The feedback network is supposed to introduce no phase shift, or 0° phase shift, however, the amplifier introduces a 180° phase change into the circuit, as seen in Fig. 2. As a result, the input signal (Vin) and the feedback voltage (Vf) are 180° out of phase. Fig. 2 Illustration of the negative feedback amplifier. Source: Rakesh Kumar, Ph.D. Advantages of Negative Feedback AmplifierA negative feedback amplifier provides several benefits, including lower distortion, more stable gain, wider bandwidth, and better input and output impedances. Negative feedback is used in amplifiers and other control circuits to improve stability. Gain StabilityGain is defined as the ability of a circuit to increase the power or amplitude of a signal. Gain is the ratio of output to input signal in an amplifier and can be expressed as A, as shown in the equation. It can be a voltage gain, a current gain, or a power gain. Gain is typically a unitless measurement.A = Vout / Vin Negative voltage feedback improves the stability of amplifier gain by making it independent of transistor characteristics and supply voltage fluctuations. Desensitizing the gain refers to making the overall gain of an amplifier less sensitive to variations in the amplifier's internal components or operating conditions. The gain only depends on the feedback circuit's parameters. Feedback circuits, which are typically resistive networks, are not impacted by temperature, transistor settings, or frequency changes. Consequently, the gain of the amplifier is extremely stable. This is one of the key benefits of using negative feedback in amplifiers. Non-Linear DistortionNegative feedback plays a crucial role in reducing non-linear distortion and makes the gain of the amplifier almost constant. It helps maintain a more proportional relationship between input and output signals, reducing non-linear distortions that occur when the amplifier operates outside its linear region. Improved BandwidthNegative feedback improves the frequency response and extends the bandwidth of the amplifier. This ensures that the amplifier can handle a wider range of frequencies more effectively, maintaining consistent gain across the spectrum. Input and Output ImpedanceNegative feedback in amplifiers significantly influences both input and output impedances, enhancing the overall performance and stability of the amplifier. NoiseDepending on whether a transistor or tube is employed, an amplifier might have a variety of noise sources. Negative feedback helps reduce the noise in the output signal. To conclude, negative feedback lowers the amplifier's gain. At the same time, negative feedback reduces distortion and noise. This trade-off is generally beneficial, as the improved linearity and reduced distortion often outweigh the loss in gain. A feedback amplifier to considerLM6172The LM6172 is a high-speed, low-power, low-distortion, dual-voltage feedback amplifier designed by Texas Instruments. It is particularly noted for its excellent DC and AC performance, making it suitable for a wide range of applications. The LM6172 boasts a very high slew rate of 3000 V/μs, which allows it to handle rapid changes in input signals without significant delay. It has a unity-gain bandwidth of 100 MHz, ensuring stable operation even at high frequencies.The amplifier is designed to operate efficiently, consuming minimal power, which is crucial for battery-operated and portable devices. The LM6172 features low total harmonic distortion and can operate over a wide supply voltage range from ±2.5V to ±18V, providing flexibility for various design requirements. It operates over a broad temperature range from -55°C to 125°C, making it suitable for industrial and military applications. The LM6172 is available in various packages, including 8-DIP and surface-mount options, providing flexibility for different design and manufacturing requirements. Summarizing the Key PointsFeedback amplifiers play a crucial role in enhancing the efficiency and stability of amplification circuits in electronics.Understanding the types of feedback, such as positive and negative, is essential for optimizing signal amplification.Negative feedback offers benefits like reduced distortion, improved stability, wider bandwidth, and enhanced input/output impedances.The LM6172 amplifier by Texas Instruments exemplifies a high-speed, low-power, low-distortion feedback amplifier suitable for various applications. ReferenceAyobamidele, Segun & Oyebola, Blessed. (2018). Feedback Amplifier, Its Operation, Effect Importance and Connecting Types: A Review. 16-32.ALL ABOUT ELECTRONICS, “Introduction to Feedback Amplifier | The concept of Negative Feedback and its advantages,” July 7, 2024, https://www.youtube.com/watch?v=__8f6AXenYo.

A*STAR Institute of Microelectronics (IME) and Cubic Micro today announce that they have developed and demonstrated a 400 MHz radio frequency (RF) transceiver with the highest power efficiency and leading performance reported to deliver high quality signals over industry's widest coverage in wireless sensor network applications. The transceiver is integrated with a highly configurable baseband, which allows users to customize transceiver performance for specific applications ranging from wireless smart energy management and security control in homes and buildings to long-range remote industrial monitoring.To achieve low power consumption in RF transceiver, performance is typically sacrificed, resulting in degradations of sensitivity, channel selectivity and interference immunity during the wireless signal communication process.To address the performance and power consumption dilemma, the IME team has employed a low-power low-noise linear RF chain and a 75-dB-dynamic-range band-pass analogue-to-digital converter (ADC) so that channel filtering is conducted in the low-power digital circuits. This strategy cuts energy consumption by up to 55% while providing unprecedented wireless communication range that supports highest reported sensitivity along with excellent selectivity compared to commercially available RF transceiver integrated chips. These features translate into fewer sensor nodes to achieve similar network coverage in a wireless sensor network, further reducing costs and power consumption.The design is amenable to mass production and is compatible with both Japanese standards[1], while also meeting the emission limits of Europe and US."IME's commitment to continually demonstrate strong R&D capabilities in CMOS RF design has attracted partners who look forward to developing next-generation smart energy metering solutions," said Professor Dim-Lee Kwong, Executive Director of IME. "We look forward to strengthening customer adoption to benefit the community with a wider range of innovative applications.""We are glad to have developed the lowest power and high performance RFIC in Asia together with IME," said Mr Yutaka Kumagai, Managing Director of Cubic Micro. "This kind of joint developments will be needed for high diversity business environment, and we believe IME will be one of the best technology partners in the area of wireless solution to create new product and technologies."Reference:BC417143B-GIQN-E4CC430F5147IRGZTLMX9838SBX/NOPB