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In the world of electronics, the reliability of components is essential for ensuring the smooth functioning of devices. Whether you're operating a smartphone, driving a car, or managing a complex industrial system, you can be certain that precise control over temperature is vital. One of the unsung heroes in achieving this control is the Negative Temperature Coefficient (NTC) thermistor.NTC thermistors are small, yet powerful components that help manage temperature in a vast array of applications, from everyday consumer electronics to high-performance systems. These devices sense temperature changes and regulate electrical resistance accordingly, offering both temperature measurement and protection capabilities. In this article, we'll explore what NTC thermistors are, how they work, and their various applications. Whether you're a seasoned engineer or a newcomer to the world of thermistors, this guide will provide you with a thorough understanding of these components and their importance in modern electronics. What Is an NTC Thermistor?To start, it's important to understand the basic concept behind NTC thermistors. A thermistor is a type of resistor whose resistance varies significantly with temperature. Unlike standard resistors, whose resistance remains constant, thermistors are temperature-dependent.NTC thermistors, specifically, have a negative temperature coefficient, which means that their resistance decreases as the temperature increases. This is the opposite of Positive Temperature Coefficient (PTC) thermistors, whose resistance increases as temperature rises. The key characteristic of NTC thermistors lies in their ability to offer precise temperature control, making them crucial for temperature sensing and circuit protection in a variety of devices. How NTC Thermistors WorkNTC thermistors function based on the principle that their resistance is inversely proportional to temperature. When the temperature of the thermistor increases, its resistance decreases. The relationship between resistance and temperature is not linear, but exponential, which is mathematically described by the following formula:Where:R(T) is the resistance at temperature T,R0 is the resistance at a reference temperature,B is the material constant specific to the thermistor,T is the temperature in Kelvin.In simpler terms, as the temperature rises, the resistance of the NTC thermistor falls dramatically. This property is what makes these thermistors particularly effective in applications where precise temperature sensing or regulation is necessary. Key Characteristics of NTC ThermistorsNTC thermistors are characterized by several key attributes that define their functionality and performance:High Sensitivity: The resistance of an NTC thermistor changes significantly with even small changes in temperature. This high sensitivity makes them ideal for measuring temperature accurately in a range of applications, from consumer electronics to industrial systems.Non-linearity: Unlike linear temperature sensors, NTC thermistors exhibit a non-linear resistance-temperature relationship. This makes them well-suited for applications where a large change in resistance is needed for a relatively small change in temperature.Self-heating: Like all resistive components, NTC thermistors generate heat as current passes through them. This self-heating effect can influence their behavior, especially when used in circuits with high current. Careful consideration of current ratings is essential to prevent thermal damage.Stability and Reliability: NTC thermistors are known for their long-term stability and reliability, making them suitable for both consumer-grade devices and high-performance applications that require consistent performance over time. Common Applications of NTC ThermistorsThe versatility of NTC thermistors has led to their widespread use in various applications. Let's take a closer look at some of the most common uses:1.Temperature SensingOne of the primary applications of NTC thermistors is temperature sensing. Because their resistance changes predictably with temperature, they are often used in temperature measurement devices, including:Thermometers: NTC thermistors are commonly used in digital thermometers for both medical and industrial applications. Their sensitivity allows them to measure small variations in temperature with high precision.Home Appliances: Many household appliances, such as refrigerators, ovens, and air conditioners, use NTC thermistors to monitor and regulate internal temperatures. The thermistors provide feedback to the control systems, ensuring that the devices operate within safe temperature ranges.Automotive Sensors: In automotive systems, NTC thermistors are used to monitor the temperature of components like engine coolant, exhaust gases, and battery packs. Accurate temperature measurement is crucial for maintaining optimal engine performance and preventing overheating. 2.Inrush Current LimitingWhen electrical devices are powered on, they can experience an inrush current – a brief surge in current that occurs as capacitors charge and other components initialize. This surge can be harmful to the components, potentially causing damage or shortening their lifespan.NTC thermistors help limit this inrush current by offering high resistance when first powered on. The high resistance reduces the initial current flow, protecting sensitive components from damage. As the thermistor heats up, its resistance decreases, allowing normal current to flow.This property makes NTC thermistors ideal for use in power supplies, surge protectors, and devices with large capacitive loads, such as audio amplifiers or power converters. 3.Battery Management SystemsIn battery-powered devices, temperature control is critical for maintaining battery health and performance. Overheating can reduce the lifespan of batteries or cause them to fail entirely. NTC thermistors are used in battery management systems to monitor the temperature of battery packs in devices such as smartphones, laptops, and electric vehicles.By constantly monitoring the temperature of the battery, the thermistor ensures that the battery operates within safe limits. If the temperature rises too high, the system can trigger a cooling mechanism or shut down the device to prevent damage. 4.Overheating ProtectionNTC thermistors are also widely used in circuit protection applications. In devices with high-power circuits, such as power supplies and motors, the thermistors help prevent overheating by regulating the current flow based on temperature changes. If the temperature exceeds a preset threshold, the thermistor's resistance increases, limiting the current and preventing further heating. 5.Consumer ElectronicsFrom smartphones to laptops, NTC thermistors are integrated into nearly all modern electronic devices. They are used not only for temperature sensing but also for ensuring the thermal protection of critical components. In devices with high-performance processors or graphics units, such as gaming consoles or computers, NTC thermistors monitor the temperature to prevent overheating and maintain consistent performance. Choosing the Right NTC ThermistorSelecting the right NTC thermistor is crucial to ensuring that your device operates as intended. When choosing an NTC thermistor, several factors need to be considered:1.Temperature RangeNTC thermistors are available in a variety of temperature ranges, from low to high temperatures. It's important to select a thermistor that can operate within the temperature range of your application. For example, automotive applications require thermistors with a higher temperature tolerance compared to consumer electronics.2.Resistance ValueThe resistance value of an NTC thermistor should be chosen based on the requirements of the circuit. A higher resistance provides better sensitivity to temperature changes, but it also results in slower response times. For applications requiring quick temperature measurements, lower resistance thermistors may be more appropriate.3.B-ValueThe B-value is a constant that defines the relationship between resistance and temperature. A higher B-value indicates that the thermistor will exhibit a more significant change in resistance per unit of temperature change. This property is essential for applications requiring high sensitivity.4.Size and Form FactorThe size and shape of the thermistor also matter. Surface-mount thermistors are ideal for compact electronic devices, while larger disc thermistors are better suited for power supply applications. Consider the available space in your design when choosing the form factor. ConclusionNTC thermistors are critical components in modern electronics, offering temperature sensing, circuit protection, and inrush current limiting capabilities. Their sensitivity to temperature changes and reliable performance make them invaluable in applications ranging from consumer electronics to industrial systems. By understanding the fundamental properties and applications of NTC thermistors, you can ensure that your electronic designs are more efficient, reliable, and long-lasting.At Kynix Semiconductor, we offer a wide selection of high-quality NTC thermistors to suit a variety of applications. Whether you're designing a temperature-sensing circuit for a medical device or need an inrush current limiter for a power supply, we have the right thermistor for you. Explore our catalog today and discover how our components can help optimize your designs for superior performance.
Allen On 2024-11-19
Exploring the BasicsA potentiometer, stands as a pivotal component in the realm of electronic engineering and design. This three-terminal resistor with its adjustable sliding or rotating contact forms the cornerstone of a versatile voltage divider system. Its widespread application across electronic circuits is largely attributed to its capability to modify voltage and provide variable resistance seamlessly. At its core, the device operates on a straightforward principle: adjusting voltage levels across its terminals through the manipulation of resistance. This functionality not only makes it an indispensable tool in adjusting the volume of audio devices but also extends its utility to serve as a critical control input for a myriad of electronic devices. From the fine-tuning of musical instruments to the precise calibration of measuring tools, its applications are as varied as they are vital. The intrinsic value of these components lies in their simplicity and effectiveness. By offering a hands-on approach to controlling electronic circuits, they empower users and technicians alike to make adjustments in real-time, ensuring optimal performance and precision in a wide range of applications. Diverse ApplicationsBeyond the basic function of volume control in audio equipment, these components find their place in a spectrum of applications, marking their importance across consumer electronics and industrial control systems alike. Their versatility is showcased in their ability to act as tuning dials on radios, offering users the tactile feedback required for fine-tuning frequencies, and as integral parts of user interfaces on various electronic devices. In the realm of industrial applications, their role becomes even more pronounced. Here, they are not just components; they are the backbone of machinery control systems, allowing for the precise calibration and adjustment of electrical signals. This precision plays a crucial role in the seamless operation of complex machinery, ensuring both efficiency and safety in industrial environments. Their adaptability and ease of integration into electronic circuits make them an invaluable tool in the designer's arsenal, offering both simplicity and precision in control mechanisms. Whether it's adjusting the backlight on a digital device or calibrating the input signals for a piece of high-precision equipment, their applications are limited only by the imagination and needs of the user. The Operational MechanicsUnderstanding the operation of these devices requires a closer look at their construction. Comprising a resistive element, a wiper (or slider), and three terminals, their design is both simple and effective. The magic happens when the wiper traverses the length of the resistive element, altering the resistance between the terminals. This action, in turn, adjusts the voltage output across the load, offering a nuanced control over the circuit's performance. The beauty of this system lies in its direct impact on a circuit without the need for altering the circuit's fundamental design. By simply adjusting the position of the wiper, users can fine-tune the output, affecting changes in volume, brightness, or signal strength with ease and precision. This level of control is particularly beneficial in applications requiring a high degree of accuracy and adaptability, from the calibration of audio equipment to the adjustment of light intensities in LED displays. The efficiency and effectiveness of these components are underscored by their ability to offer real-time adjustments in a user-friendly manner. Whether it's a subtle change in the ambient lighting of a room or a critical adjustment in the feedback loop of an industrial control system, the potentiometer stands as a testament to the elegance of simplicity in design and functionality. Varieties of Potentiometers: Understanding the DifferencesIn the vast and intricate world of electronic components, potentiometers distinguish themselves not just by functionality but also by their diverse forms, each tailored to specific needs and applications. Among the plethora, rotary, linear, and digital variants stand out, each with its unique advantages and suited environments. Rotary variants are perhaps the most visually recognizable, embodying the classic control knob found on numerous devices. Their design is geared towards applications where user interaction involves circular motion, making them ideal for volume control in audio systems or tuning dials in broadcasting equipment. The tactile feedback and intuitive operation of rotary types make them a favorite in user-interface design. Linear versions, by contrast, operate on a straight-line path, making them perfect for applications where precise and direct control is needed. From the sliders on mixing consoles to position controls in machinery, their design allows for straightforward and accurate adjustments. Their application in fields that require a tangible correlation between control position and effect, such as lighting dimmers or motor controls, highlights their versatility. Digital potentiometers represent the confluence of traditional mechanical design and modern digital technology. Offering electronic control, they bring precision, programmability, and the ability to interface with microcontrollers and other digital systems. Their use is critical in environments where adjustments need to be made with pinpoint accuracy, or where automation and remote control are necessary. This integration of digital control mechanisms allows for complex adjustments to be made simpler and more efficient, making them invaluable in advanced electronic systems. Understanding Resistance ValuesThe resistance value of these components is a defining characteristic that influences their application and functionality. Measured in ohms, this value can span from just a few ohms to several megaohms, reflecting the wide range of uses and the versatility of these devices. Selecting the appropriate resistance value is crucial, as it determines the range of adjustment available and the maximum current the device can safely handle. This selection process is guided by the specific requirements of the application, whether it's a delicate adjustment in a high-precision instrument or a robust application in an industrial setting. The choice of resistance value directly impacts the performance and efficiency of the application. In audio equipment, for example, a well-chosen value can mean the difference between clear, precise volume control and a system prone to distortion or imbalance. Similarly, in industrial applications, the right resistance value ensures that controls respond accurately and reliably under varying conditions. CharacteristicsDelving deeper into the characteristics of these components, we find that resistance value, tolerance, power rating, and linearity are key to their performance. Tolerance is a measure of precision, indicating how closely the actual resistance value aligns with the specified value, a critical factor in high-precision applications. The power rating is equally important, denoting the maximum power the device can handle without risk of damage or failure, ensuring longevity and reliability in its operation. Linearity, or the uniformity of the resistance change as the adjustment is made, is paramount in applications requiring precise control. Non-linear adjustments can lead to unpredictable results, making this characteristic vital in settings where accuracy is non-negotiable. The balance between these characteristics defines the suitability of a potentiometer for a given application, making understanding them crucial for engineers and designers alike. ConclusionIn the ever-evolving world of electronics, potentiometers maintain their crucial status as fundamental components capable of precisely controlling and adjusting electrical parameters. Their significance within the industry is bolstered not only by their basic functionality but also by their ability to adapt to the rapid pace of technological progress and the shifting requirements of diverse applications. Gaining a deep understanding of how they operate, the variety of forms they come in, and the importance of their key features is vital for anyone seeking to utilize these components effectively. As they continue to evolve and find new roles within both established and emerging technologies, their contribution to electronics design and functionality becomes increasingly pronounced, showcasing their perpetual value and versatility. FAQsWhat is a potentiometer? A potentiometer is a three-terminal resistor used in electronic circuits to adjust voltage levels and provide variable resistance. What are the main types of potentiometers? The main types are rotary, linear, and digital variants, each offering unique advantages for different applications. How do potentiometers work? Potentiometers work by adjusting resistance via a sliding or rotating contact, allowing users to modify voltage outputs in electronic circuits. What are the applications of potentiometers? They are widely used for volume control in audio devices, tuning dials in radios, and precise calibration in industrial machinery control systems. What factors should be considered when selecting a potentiometer? Important factors include resistance value, tolerance, power rating, and linearity, which determine suitability for specific applications. Why are potentiometers important in electronics? Potentiometers offer simplicity, versatility, and precision in controlling electronic circuits, making them indispensable components across a wide range of applications.
Allen On 2024-02-29
Executive Summary: Transistors in 2026The semiconductor transistor remains the fundamental building block of modern electronics. As of January 2026, the industry has shifted toward Gate-All-Around (GAAFET) architectures at the 2nm process node, enabling AI chips like NVIDIA's Blackwell B200 to pack over 208 billion transistors. This guide updates legacy concepts with 2026 standards, covering operation modes, NPN/PNP switching circuits, and the latest market statistics approaching a $1 Trillion valuation.What is a Semiconductor Transistor in 2026?A semiconductor transistor is an active semiconductor device used to amplify, control, and generate electrical signals and power. It functions as a variable current switch capable of controlling output current based on input voltage. Unlike ordinary mechanical switches (such as relays), transistors use electrical signals to control their own opening and closing, allowing for switching speeds in the gigahertz (GHz) range—critical for modern 5G and AI applications.Key 2026 Insight: While traditional Bipolar Junction Transistors (BJTs) are still used in analog circuits, modern high-speed computing relies on GAAFET (Gate-All-Around Field Effect Transistor) technology, which has replaced FinFET at the 3nm and 2nm nodes to minimize power leakage.Video: Transistors Basics Explained Ⅰ How do Electrons and Holes Function in a Transistor?The transistor is a current-controlled device (BJT) or voltage-controlled device (FET) that facilitates signal amplification, oscillation, and modulation. Its operation relies on the movement of charge carriers: electrons (negative charge) and holes (positive charge carriers).A standard BJT has three terminals (Emitter, Base, Collector), three regions, and two PN junctions. Understanding the internal structure is key to grasping how 2026 hardware manages billions of switching operations per second.Figure 1. Transistor Structure (NPN Configuration)Movement of Charge Carriers:Figure 2. Movement of Charge CarriersHoles vs. Electrons: The hollow circles in Figure 2 represent positively charged holes, while solid dots are negatively charged electrons. "Hole movement" is effectively the macroscopic result of electrons filling vacancies.Emitter (E): Heavily doped to emit a large number of electrons. When forward-biased, it injects carriers into the base.Base (B): Very thin and lightly doped. In an NPN transistor, the P-type base allows most electrons from the emitter to diffuse directly to the collector, with very few recombining with holes (creating the small base current, IB).Collector (C): Large surface area designed to collect electrons drifting through the base. It dissipates the most heat, especially in power transistors used in 2026 EV inverters.Current Equation: IE (Emitter Current) = IC (Collector Current) + IB (Base Current).Ⅱ What are the Key Characteristics of Transistors?Transistors define the logic of all digital circuits. Their behavior is governed by the following core principles:1) Current Control (BJT): The small base current (IB) controls the large collector current (IC).NPN Current Direction: Base → Emitter.PNP Current Direction: Emitter → Base.2) Amplification Factor (β): Transistors amplify signals by a factor of β (Beta). If IB = 1mA and β = 100, then IC = 100mA. This principle amplifies weak sensor signals in IoT devices.3) Saturation (Switch ON): When IB is sufficient (e.g., ≥1mA for small signal transistors), the voltage drop Vce ≈ 0.3V. The transistor acts as a closed switch.4) Cutoff (Switch OFF): When Vbe < 0.7V (for Silicon), the transistor is fully off. Vce is high (equal to supply voltage), acting as an open switch.Design Tip for 2026: For NPN switching circuits, connect the load to the Collector and the Emitter to Ground (GND). For PNP, connect the Emitter to Power (VCC) and the load to the Collector. NPN is generally preferred in modern logic due to higher electron mobility compared to hole mobility. Ⅲ What are the Three Operational Regions of a Transistor?To effectively use a transistor in AI hardware or power regulators, one must understand its three operational states: Cut-off, Active, and Saturation.Figure 3. Transistor Circuit And Operational Regions(1) Cut-off Region (Digital "0"): The transistor is OFF. Ube < Threshold (0.7V). IB = 0, IC ≈ 0. The switch is open.(2) Active Region (Amplification): Used for analog signal processing (audio, radio). The Emitter junction is forward-biased, and the Collector junction is reverse-biased. IC = β * IB.(3) Saturation Region (Digital "1"): The transistor is fully ON. Both junctions are forward-biased. IC cannot increase further even if IB increases. Uce is minimal (~0.2V).In embedded systems and logic gates (like those in the newest 2nm chips), transistors toggle rapidly between Cut-off and Saturation, avoiding the Active region to minimize power loss.Figure 4. Voltage CharacteristicⅣ How to Analyze Input and Output Characteristics?4.1 Input CharacteristicsThe input characteristic curve relates the base current (IB) to the base-emitter voltage (VBE). It resembles the curve of a standard diode.Figure 5. Input CharacteristicWhen VCE increases, the collector's ability to "sweep" electrons improves, slightly reducing the recombination in the base. This shifts the curve to the right, meaning less IB flows for the same VBE.4.2 Output CharacteristicsThe output characteristic relates the collector current (IC) to the collector-emitter voltage (VCE) for various fixed values of IB.Figure 6. Output CharacteristicUnderstanding the Graph: The horizontal axis is VCE. The initial steep rise is the Saturation Region (switch closed). The flat horizontal lines represent the Active/Amplification Region, where IC is constant regardless of VCE (acting as a constant current source controlled by IB). Ⅴ What Causes Saturation and Cutoff Distortion?Signal distortion occurs when a transistor amplifier is improperly biased, causing the output waveform to be "clipped" at the top or bottom.5.1 Waveform Analysis of Basic Common Emitter Amplifier CircuitFigure 7. Waveform Analysis of Common-emitter Amplifier CircuitSaturation Distortion (Bottom Clipping): Occurs when the static operating point (Q-point) is too high. IB is too large, causing UCE to drop near 0V during the positive half-cycle of the input.Cutoff Distortion (Top Clipping): Occurs when the Q-point is too low. IB is too small, causing the transistor to turn OFF during the negative half-cycle of the input.5.2 Why use Transistors as Switches?Feasibility: The distinct "ON" (Saturation) and "OFF" (Cutoff) states allow transistors to replace mechanical switches. Modern SiC (Silicon Carbide) transistors can switch high voltages in EVs with minimal efficiency loss.Necessity: Microcontrollers (CPUs/MCUs) operate at low voltages (3.3V or 5V) and cannot directly drive high-power loads like motors or LED arrays. A transistor acts as the bridge, allowing a weak software signal to control massive power. Ⅵ How to Design Transistor Switching Circuits?6.1 Basic Switching Circuit of NPN TransistorsFigure 8. NPN Transistor Switch CircuitLow-Side Switching: In an NPN circuit, the Load (R1) is connected between VCC and the Collector. The Emitter connects to Ground. When the Base receives a High signal (e.g., 3.3V from a GPIO pin), current flows from C to E, turning the load ON.6.2 Basic Switching Circuit of PNP TransistorsFigure 9. Basic Switching Circuit of PNP TransistorHigh-Side Switching: Common PNP models like the 8550 are used here. The Emitter connects to VCC. The Load connects between the Collector and Ground. Logic: A LOW signal (0V) at the Base turns the PNP transistor ON. A HIGH signal turns it OFF. This is often used for driving buzzers or indicators where the ground path must remain common. Ⅶ Frequently Asked Questions About Transistors (2026 Update)1. How does a semiconductor transistor work?A transistor works by using a small control current at the Base (or voltage at the Gate) to regulate a much larger current flowing between the Collector and Emitter (or Source and Drain). This allows it to act as an amplifier or a high-speed electronic switch.2. How is a transistor used as a switch?The transistor operates as a solid-state switch by toggling between the Cutoff region (Open circuit, OFF) and the Saturation region (Short circuit, ON). It eliminates moving parts, allowing for billions of operations per second in modern CPUs.3. What is the PN junction of a transistor?A BJT contains two PN junctions. The Emitter-Base junction is forward-biased to inject carriers, while the Collector-Base junction is typically reverse-biased to collect them. These junctions form the potential barriers that control current flow.4. How many PN junctions are there in a transistor?2 PN JunctionsA Bipolar Junction Transistor (BJT) has two PN junctions (Base-Emitter and Base-Collector). Field Effect Transistors (FETs) rely on channel conductivity rather than junction injection.5. What are the two basic types of transistors?The two primary categories are Bipolar Junction Transistors (BJT) (current-controlled) and Field Effect Transistors (FET) (voltage-controlled). As of 2026, FETs (specifically MOSFETs and GAAFETs) dominate digital electronics.6. What are the terminals of a transistor called?For BJTs: Emitter, Base, and Collector. For FETs/MOSFETs: Source, Gate, and Drain.7. What is the difference between NPN and PNP?An NPN transistor turns ON with a positive current to the Base (High-Side control usually requires voltage > Emitter). A PNP transistor turns ON when the Base is pulled Low (voltage < Emitter). NPN is more common in switching applications due to better electron mobility.8. What is the most popular transistor in 2026?The MOSFET remains the most widely used transistor globally, accounting for 99.9% of all transistors. However, for cutting-edge AI chips (like NVIDIA Blackwell), GAAFET (Gate-All-Around) is the new standard, while SiC and GaN dominate power electronics in electric vehicles.{ "@context": "https://schema.org", "@type": "Article", "headline": "What is a Semiconductor Transistor? 2026 Comprehensive Guide", "datePublished": "2019-01-01", "dateModified": "2026-01-05", "description": "A deep dive into semiconductor transistors, covering electrons/holes, NPN/PNP characteristics, and 2026 industry standards like GAAFET and AI chip architectures.", "author": { "@type": "Organization", "name": "Kynix Semiconductor" }, "mainEntity": { "@type": "FAQPage", "mainEntity": [ { "@type": "Question", "name": "How does a semiconductor transistor work?", "acceptedAnswer": { "@type": "Answer", "text": "A transistor works by using a small control current at the Base (or voltage at the Gate) to regulate a much larger current flowing between the Collector and Emitter, effectively acting as an amplifier or switch." } }, { "@type": "Question", "name": "What are the two basic types of transistors?", "acceptedAnswer": { "@type": "Answer", "text": "The two main types are Bipolar Junction Transistors (BJT) and Field Effect Transistors (FET). In 2026, FETs (specifically MOSFETs and GAAFETs) are the dominant technology for digital processors." } }, { "@type": "Question", "name": "How acts a transistor as a switch?", "acceptedAnswer": { "@type": "Answer", "text": "It acts as a switch by driving the transistor into saturation (fully ON) or cutoff (fully OFF), thereby completing or breaking the circuit path for the load." } }, { "@type": "Question", "name": "What is the difference between NPN and PNP transistors?", "acceptedAnswer": { "@type": "Answer", "text": "NPN transistors are 'active high' switches that turn on when current enters the base. PNP transistors are 'active low' switches that turn on when the base is pulled to ground." } } ] }}
Kynix On 2022-03-10
Introduction When the reverse bias voltage applied to the PN junction increases to a certain value, the phenomenon that the reverse current density suddenly begins to increase rapidly is called PN junction breakdown. From the mechanism, it can be divided into three categories: avalanche breakdown, tunnel breakdown and thermoelectric breakdown. Among them, there are two physical mechanisms for forming reverse breakdown in PN junction: zener breakdown and avalanche breakdown. Generally, both breakdowns coexist. So what is the difference between them? Avalanche Breakdown and Zener Breakdown Effect Explained Catalog Introduction Ⅰ Basic Characteristics 1.1 Avalanche Effect 1.2 Zener Effect Ⅱ Zener Effect vs Avalanche Effect Ⅲ Transistor Secondary Breakdown and Protection 3.1 A Brief Description 3.2 Cause of Breakdown 3.3 Precaution 3.4 Snubber Circuit Examples Ⅳ FAQ Ⅰ Basic Characteristics 1.1 Avalanche Effect As the reverse voltage increases, the electric field in the space charge region strengthens, and the energy obtained by the carriers in the barrier region also increases. When the reverse voltage is close to the breakdown voltage, these carriers with higher energy meet the neutral atoms in the space charge region and cause collision ionization, generating new electron-hole pairs. These newly generated electrons and holes will regain energy under the action of the electric field, collide with other neutral atoms to ionize them, and generate more electron-hole pairs. With reaction continues, causing the number of carriers in the space charge region to increase sharply, just like an avalanche, what’s more, the reverse current also increase sharply, resulting in breakdown. So this breakdown is called avalanche breakdown (or avalanche effect).This breakdown generally occurs in PN junctions with lower doping concentration and higher applied voltage. Because a PN junction in this state has a wider space charge region and more opportunities for impact ionization. Figure 1. Zener Breakdown vs Avalanche Breakdown 1.2 Zener Effect When the reverse voltage increases to a certain value, a strong electric field can be established in the barrier region, which can directly pull out the valence electrons bound in the covalent bond, so that a large number of electron-holes are generated in the barrier region. Then a large reverse current is formed, resulting in breakdown. At this time, atoms in the barrier region are directly excited under the action of a strong electric field is called Zener effect/breakdown. It is caused by the tunneling effect in quantum mechanics. Giving a simple metaphor, the simple understanding is that the two lines are too close, and they pass through directly. At this time, the potential barrier loses its function of blocking electrons, and a breakdown occurs.Zener breakdown generally occurs in PN junctions with higher doping concentrations. This is because the PN junction under this situation has a large charge density and a narrow width in the space charge region. As the temperature increases, the energy gap decreases, and a breakdown can be resulted in with a small reverse voltage. Figure 2. PN Junction Ⅱ Zener Effect vs Avalanche Effect 1) Zener effect mainly depends on the maximum electric field in the space charge region, and in the collision ionization mechanism is related to both the field strength and the collision accumulation process of carriers. Obviously, the wider the space charge region, the more times of multiplication, so the avalanche breakdown is not only related to the electric field, but also related to the width of the space charge region, which requires the thickness of the PN junction.2) Because avalanche breakdown is the result of impact ionization. If we increase the electrons and holes in the space charge region by means of illumination or fast particle bombardment, they will also have a multiplier effect. However, the above external effects will not have a significant impact on the Zener breakdown.3) The breakdown voltage is determined by the tunnel effect, and its temperature coefficient is negative, that is, the breakdown voltage decreases with the increase of temperature, which is the result of the decrease of the forbidden band width with the increase of temperature. The breakdown voltage determined by avalanche multiplication decreases with the increase of temperature due to the impact ionization rate (the ionization rate represents the number of electron-hole pairs generated by a carrier drifting a unit distance under the action of an electric field), and its temperature coefficient is positive. That is, the breakdown voltage increases with temperature. Zener with voltage lower than 5-6V is mainly due to Zener breakdown; Zener with voltage higher than 5-6V is mainly due to avalanche breakdown. Zener diodes with a voltage between 5-6V have similar breakdown degrees and the best temperature coefficient, which is why many circuits use 5-6V Zener tubes. The principle of the Zener tube determines that its response speed is not very fast, so a tube reference voltage is used in occasions with high speed requirements.4) For the PN junction with higher doping concentration and thinner barrier, it is mainly Zener breakdown. The PN junction with lower doping and therefore wider potential barrier is mainly avalanche breakdown, and the breakdown voltage is relatively high.The PN junction breakdown is an important electrical property, and the breakdown voltage limits the working voltage of the circuit, so semiconductor devices have certain requirements for the breakdown voltage. However, a variety of devices such as Zener diodes, avalanche diodes, and tunnel diodes can be fabricated by using the breakdown phenomenon.Under normal circumstances, the avalanche breakdown and Zener breakdown are within a certain range of conditions (breakdown voltage, time), with the normal working conditions are restored, are reversible. If it is only for protection, the TVS voltage regulator tube is mainly used for voltage regulation. The smaller the current passing through, the better. When the instantaneous voltage exceeds the normal working voltage of the circuit, the TVS diode will avalanche, providing an ultra-low resistance path for the instantaneous current, which is diverted through the diode, avoiding the protected device. In additional, the protected circuit keeps the cut-off voltage until the voltage returns to normal value. When the instantaneous pulse ends, the TVS diode automatically returns to the high resistance state, and the entire circuit entering the normal voltage, the failure mode of the TVS tube is mainly short circuit. But when the overcurrent passed is too large, it may also cause the TVS tube to be burst and open. Figure 3. TVS Diode Ⅲ Transistor Secondary Breakdown and Protection 3.1 A Brief Description In most switching power supplies, power switching transistors work under high-voltage, high-current high-frequency pulses, and switching on and off under such conditions will cause a great impact on the transistors. Secondary breakdown is one of the important causes of transistor damage. To design a high-performance, high-reliability switching power supply, it is necessary to have a clear understanding of the secondary breakdown of transistors and avoidance measures. 3.2 Cause of Breakdown The secondary breakdown is mainly caused by the high local temperature in the device body. The temperature rise is caused by thermal imbalance when forward biased and avalanche breakdown when reverse biased.Because the thermal resistance of the transistor is unevenly distributed throughout the tube, in some weak areas, the temperature rise will be higher than other parts, forming a so-called "hot spot", and so on until a critical temperature, causing the breakdown of the tube. The secondary breakdown caused by the avalanche breakdown is a phenomenon in which the electric field distribution of the junction is changed due to the excessive current density at some points after the primary avalanche breakdown occurs, resulting in a negative resistance effect and the local temperature is too high. 3.3 Precaution Turn-on and turn-off losses are important factors that affect the normal operation of switching devices. In particular, the transistor is prone to secondary breakdown in the dynamic process, and this phenomenon is directly related to the switching loss. Therefore, reducing the switching loss of the self-shutdown device is a necessary measure for the correct use of the device. There are two ways to reduce losses:(1) Turn off the transistor at the lowest possible collector-emitter voltage (Vce).(2) When the transistor is turned off during the rise of the emitter voltage, the emitter current should be minimized. For example, introducing a buffer circuit is one of the ways to achieve the above purpose. 3.4 Snubber Circuit Examples The following snubber circuits can be used in the design of switching power supplies to ensure that the transistors operate within a safe area.1) The commonly one is an energy-consuming shutdown snubber circuit. Although it consumes more energy, this circuit is simple. Figure 4. Commonly Used Shutdown Snubber Circuit It consists of an RCD network connected in parallel with transistor switches. When the transistor is turned off, the load current charges the capacitor C through the diode D, so that the collector current of the tube gradually decreases. Because the voltage across the capacitor C cannot be abruptly changed, its collector voltage is restrained. The situation where the collector voltage and current reach their maximum values at the same time is avoided, so there is no maximum instantaneous power consumption spike. When the tube is turned on, the capacitor releases energy and dissipates it in the resistor.2) Two commonly used energy-consuming turn-on snubber circuits.a. An inductor-diode network is connected in series with the transistor collector to form a turn-on snubber circuit. When the tube is turned on, the inductance Ls controls the current rise rate di/dt during the collector voltage drop. When the tube is turned off, the energy stored in the inductor Ls 1/2 freewheels through the diode Ds, and its energy is dissipated in the resistance of Ds and the reactor. Figure 5. Open Snubber Loop with Unsaturated Reactance b. Turn-on snubber circuit with saturable reactor: The purpose of using turn-on snubber circuit is to make the collector voltage drop to 0 when the collector current of the transistor is small, so as to minimize the turn-on loss. Especially for inductive loads, the effect is more significant. The designed saturable reactor should be: in one hand, after the collector voltage drops to zero, the buffer reactor is in a saturated state; in the other hand, before saturation, the collector voltage drops to zero, the reactor presents a high resistance, and the magnetizing current flowing through the tube is small to achieve the purpose of reducing turn-on loss. Figure 6. Open Snubber Circuit with Saturable Reactance 3) In the figure, Co is a transfer capacitor, and Dc is a feedback diode. These two components feed back energy to the load. When the tube is turned off, the buffer capacitor Cs is charged to the power supply voltage Vcc, and when the tube is turned on next time, the load current is transferred from the freewheeling diode Df to the transistor. At the same time, the voltage on Cs resonates to Co. When the tube is turned off again, the Cs is charged again, the capacitor Co is discharged to the load, and the energy is fed back. Figure 7. Passive Feedback Shutdown Buffer Circuit 4) This circuit stores the magnetic field energy and feeds back to the power supply through the transformer. The transformer is wound with two wires, and its primary side has a certain inductance; the polarity of the width side is opposite to that of the primary side, and a reverse diode is connected. When the tube is turned on, the primary side bears all the power supply voltage, and the secondary side has no energized circuit. When the tube is turned off, the polarity of the induced voltage on the secondary side is reversed, and when its voltage is higher than the power supply voltage Vcc, energy is fed to the power supply. Figure 8. Passive Feedback Opens the Buffer Circuit 5) The turn-on snubber circuit and the turn-off snubber circuit are combined to form a composite snubber circuit, and the composite snubber circuit has a protective effect when the transistor is turned on and off. This kind of circuit is also divided into two types: energy consumption and energy feeding.a. When the tube is turned on, the snubber capacitor is discharged through the Cs, Rs, and Ls loops, which reduces the current rising rate that the tube bears. In addition, when the tube is turned on, the inductance Ls can also limit the reverse recovery current of the freewheeling diode Df. Figure 9. Energy-consuming Composite Buffer Circuit b. When the transistor is turned off, the capacitor Co and the inductor Ls operate in parallel to feed the stored energy to the load. When the capacitor Co is discharged, the voltage on the inductor Ls gradually decreases to 0, and the load current is conducted through the freewheeling diode Df during this period. Figure 10. Energy-feeding Compound Snubber Circuit The various snubber circuits mentioned above can be divided into two types, namely energy-consuming and energy-feeding. The energy-consuming circuit is simple but relatively consumes more energy, and is suitable for the use of low-power circuits. The energy-feeding circuit is complex, but in a high-power supply, if the energy dissipated by the snubber circuit is dissipated in the form of heat, it is bound to cause a lot of trouble, so the energy-feeding buffer circuit should be used. Ⅳ FAQ 1. What is a zener breakdown voltage?A normal p-n junction diode allows electric current only in forward biased condition. ... This sudden rise in electric current causes a junction breakdown called zener or avalanche breakdown. The voltage at which zener breakdown occurs is called zener voltage and the sudden increase in current is called zener current. 2. Which breakdown occurs in Zener diode?avalanche breakdownIn Zener diodes, avalanche breakdown occurs. When the Vz is greater than 8 volts in a Zener diode, avalanche breakdown occurs because there is an isolation of electrons and holes. 3. What is difference between avalanche and zener breakdown?The main difference between Zener breakdown and avalanche breakdown is their mechanism of occurrence. Zener breakdown occurs because of the high electric field whereas, the avalanche breakdown occurs because of the collision of free electrons with atoms. Both these breakdowns can occur simultaneously. 4. How do you calculate Zener breakdown voltage?The reverse current that results after the breakdown, is called Zener current (Iz). At breakdown, increase of VI increases II by large amount, so that V0 = VI– RI II becomes constant. This constant value of V0 which is the reverse breakdown voltage, is called Zener voltage. 5. What is avalanche breakdown of diode?What is Avalanche Breakdown? The avalanche breakdown occurs when a high reverse voltage is applied across the diode. As we increase the applied reverse voltage, the electric field across the junction increases. This electric field exerts a force on the electrons at the junction and frees them from covalent bonds. 6. How does an avalanche breakdown take place?Avalanche breakdown usually occurs when a high reverse voltage is applied across the diode. So as we increase the applied reverse voltage, the electric field across the junction will keep increasing. This generated electric field exerts a force on the electrons at the junction and it frees them from covalent bonds. 7. What is avalanche effect of Zener diode?Avalanche breakdown involves minority carrier electrons in the transition region being accelerated, by the electric field, to energies sufficient for freeing electron-hole pairs via collisions with bound electrons. The Zener and the avalanche effect may occur simultaneously or independently of one another. 8. What do you mean by zener breakdown voltage?When reverse biased voltage applied to the zener diode reaches zener voltage, it starts allowing large amount of electric current. At this point, a small increase in reverse voltage will rapidly increases the electric current. Because of this sudden rise in electric current, breakdown occurs called zener breakdown. 9. Is Zener voltage the same as breakdown voltage?The breakdown voltage,commonly called the Zener voltage, is the reverse-biased voltage that causes the diode to conduct current. Breakdown voltages usually range from 2.4 V to hundreds of volts. 10. What is meant by Zener effect?The Zener effect is a type of electrical breakdown that occurs in a reverse-biased PN junction when the electric field enables tunnelling of electrons from the valence to the conduction band of a semiconductor, leading to a large number of free minority carriers which suddenly increase the reverse current. 11. Which factor is responsible for Zener effect?In effect, electrons from the p-side valence band are able to tunnel across the barrier into the empty states in the n-side conduction band when a small reverse bias is applied. The result is a strong current from n to p in the diode, causing zener breakdown. 12. What is valence breakdown?Avalanche breakdown (or “the avalanche effect”) is a phenomenon that can occur in both insulating and semiconducting materials. It is a form of electric current multiplication that can allow very large currents within materials which are otherwise good insulators. It is a type of electron avalanche.
Ivy On 2022-02-25
Introduction RF power amplifier is an important part of various wireless transmitters. In the front-end circuit of the transmitter, the power of the RF signal generated by the modulation oscillator circuit is very small, and it needs to go through a series of amplification-buffer stage, intermediate amplification stage, and final power amplification stage to obtain enough RF power before feeding. In order to obtain a sufficiently large RF output power, a RF power amplifier must be used. RF Power Amplifier Design: The Basics Catalog Introduction Ⅰ Requirements of RF Power Amplifier Ⅱ Types of Power Amplifier in Use Ⅲ Parameters of RF Power Amplifier Design Ⅳ Key Feature: Non-Linearity 4.1 Nonlinear Characteristics 4.2 Influence of Nonlinear Characteristics Ⅴ FAQ Ⅰ Requirements of RF Power Amplifier With the vigorous development of modern digital mobile communication technology, users have more requirements on the performance of wireless communication equipment. To achieve stable and high-speed data transmission in various environments is one of the main goals of future mobile communication system researchers. The RF power amplifier is the last stage of the transmitter. It amplifies the modulated frequency band signal to the required power, ensuring that the receiver in the coverage area can receive a satisfactory signal level, but it cannot interfere too much with the communication of adjacent channels, and meanwhile try to keep the amplified high-power signal without distortion. The requirements of these different aspects make the users of power amplifiers have to consider many factors in all aspects. So you should get a full knowledge of RF power amplifiers. Figure 1. Classic RF Power Amplifier Circuit Ⅱ Types of Power Amplifier in Use What are the main types of RF amplifiers for such an important device?1) According to the operating frequency bandsAccording to the working frequency band, it can be divided into narrowband RF power amplifier and broadband RF power amplifier. The former generally uses frequency selective networks as load circuits, such as LC resonant circuits. The latter does not use the frequency selection network as the load loop, but employs the transmission line with a wide frequency response as the load.2) According to the network propertiesAccording to the nature of the matching network, power amplifiers can be divided into non-resonant power amplifiers and resonant power amplifiers. The matching network of the non-resonant power amplifier is a non-resonant system, such as high-frequency transformers, transmission line transformers and other non-resonant systems, and its load properties are purely resistive, where this is also called reactance properties.3) According to current conduction angleBased on it, RF power amplifiers can be divided into class A, AB, B, C, D, E and so on. The differences between these categories can be seen in the following table: Classification Conduction Angle Efficiency Linearity Application Class A Θ=360° ≤30% Very good Small Signal Low Power Amplification Class B Θ=180° ≤60% Lower than class A For High Power Class C Θ<180° About 60% Nonlinear amplifier For High Power Class AB 180°<Θ<360° 30%~60% Better than class B Small signal works in class A, large signal works in class B Class D Work in switch mode 80% Very good, only good for low frequencies Switch mode amplifier Class E Work in switch mode 90% Completely nonlinear amp Switch mode amplifier In the classification of amplifiers, we often talk about amplifiers of class A to E according to the conduction angle. Class A power amplifier is a linear amplifier, its response to the sine-wave input is a sine-wave output, generally without distortion amplification, and the output frequency is the same as the input frequency. Since class A amplifiers do not require additional filtering circuitry, their packages can be small and cost less. The output of a class B amplifier is a half sine wave of the input, resulting in half-wave distortion, which produces many harmonics. The output power and efficiency of the class C working state are the highest among these working states, and most of the amplifiers used for radio frequency work in the class C. Figure 2. Class A Amplifier Load Curve Ⅲ Parameters of RF Power Amplifier Design RF power amplifiers are electronic circuits that comprehensively consider issues such as output power, excitation level, power consumption, distortion, efficiency, size and weight. In the transmitting system, the output power of the RF power amplifier can be as small as mW and as large as several kW, but this refers to the output power of the final power amplifier. In order to achieve high power output, the last stage must have a sufficiently high excitation power level. At the same time, it has other important indicators, as follows:1) Operating FrequencyGenerally speaking, it refers to the linear operating frequency range of the amplifier. If the frequency starts at DC, the amplifier is considered to be a DC amplifier.2) GainThe working gain is the main indicator to measure the amplification ability of the amplifier. Here it is defined as the ratio of the power delivered to the load by the amplifier output port to the power actually delivered by the signal source to the amplifier input port.Gain flatness refers to the variation range of amplifier gain in the entire operating frequency band under a certain temperature, and is also a main indicator of the amplifier. Figure 3. Output Power and 1dB Compression Point (P1dB) Referring to the Figure 3, when the input power exceeds a certain amount, the gain of the transistor begins to decrease, and the end result is that the output power saturates. When the gain of the amplifier deviates from a constant or is 1dB lower than other small signal gains, this point is the famous 1dB compression point (P1dB). Generally speaking, the power capacity of an amplifier is expressed by the 1dB compression point.3) EfficientSince the power amplifier is a power component, it needs to consume the supply current. Therefore, the efficiency of the power amplifier is extremely important to the efficiency of the whole system. Power efficiency is the ratio of the RF output power of the amplifier to the DC power supplied to the transistors.ηp=RF Output Power/DC Input Power4) Intermodulation Distortion (IMD)Intermodulation distortion refers to the mixed components of two or more input signals with different frequencies passing through a power amplifier. This is due to the nonlinear nature of the amplifier. Among them, because the third-order intermodulation product is very close to the fundamental signal, it has the greatest influence, so the third-order intermodulation is the most important consideration for the related products. The lower the third-order intermodulation product, the better.5) Third-order Intermodulation Cut-off Point (IP3)The intersection point of the extension line of the fundamental wave signal output power and the extension line of the third-order intermodulation in Fig is called the third-order intermodulation cut-off point, which is represented by the symbol IP3. It is also an important indicator of nonlinearity. When the output power is constant, the greater the output power of the third-order intermodulation cut-off point, the better the linearity of the power amplifier.6) Dynamic RangeThe dynamic range of a power amplifier generally refers to the difference between the minimum detectable signal and the maximum input power in the linear operating region. Naturally, this value must be as large as possible.7) Harmonic DistortionWhen the input signal increases to a certain level, the power amplifier will generate a series of harmonics due to its work in the nonlinear region. For high-power amplifier systems, filters are generally required to reduce harmonics below 60dBc.8) Input/Output VSWR (Voltage Standing Wave Ratio)This is also a very important indicator of how well the amplifier matches the overall system. The deterioration of the input-output ratio will lead to the deterioration of the gain fluctuation and group delay of the system. However, it is difficult to design a power amplifier with a high VSWR. In general systems, the input VSWR of the power amplifier is required to be lower than 2:1.The main technical indicators of RF power amplifiers are output power and efficiency. Therefore how to improve them is the core of the design goals of RF power amplifiers. Usually in the RF power amplifier, the fundamental frequency or a certain harmonic can be selected by the LC resonant circuit to achieve distortion-free amplification. In addition to this, the harmonic components in the output should be as small as possible to avoid interference with other channels. Figure 4. Increase the Power of the RF Input Signal Ⅳ Key Feature: Non-Linearity In an ideal amplifier, the output signal should faithfully reflect the input signal, that is, the waveform should be the same. But in fact, for many reasons, the input signal cannot be exactly the same waveform as the input signal, which is called amplifier distortion.Amplifier distortion mainly includes frequency distortion (linear distortion) and waveform distortion (non-linear distortion). The former mainly refers to the difference in gain and delay of the amplifier for different frequency components; the latter refers to the same frequency, the output signal and the input signal are not linear. Frequency distortion is represented by spectral changes in the frequency domain, while nonlinear distortion is represented by changes in the time-domain waveform. Non-linear distortion is different from frequency distortion mainly because a large number of new frequency components are generated. The nonlinear distortion of the power amplifier is mainly discussed here. 4.1 Nonlinear Characteristics From the small-signal model and input characteristic curve of an ideal transistor, it can be seen that the transistor amplifier itself is not an ideal linear device, and at the same time, due to the influence of parasitic parameters, the linearity is further reduced. But within a certain power range, the transistor can be regarded as linear amplification. For power amplifier designers, how to obtain higher output power and improve linearity is the key.For a transistor amplifier, its volt-ampere characteristics can be described as follows: A power series expansion can be used to describe the volt-ampere characteristics of the device: In the formula, an(n=0,1,2,3,…) is a coefficient related to the circuit characteristics. Usually, the larger the n, the smaller the value of the coefficient an. When the nonlinear device in the circuit is represented by a power series, the number of series terms taken depends entirely on the magnitude of the signal amplitude and the required precision. 4.2 Influence of Nonlinear Characteristics The influence of the nonlinear characteristics of the device on the amplifier can be discussed in two cases. One is when there is only one signal at the input end, and the other is when the input end has one to two other signals in addition to the useful signal.🔺Only one signal at the inputLet the signal at the input end be , and substitute it into formula 2, at this time there is When the amplitude of the input signal is large and the effect of the cubic term must be considered, the fundamental frequency signal obtained from formula 2 is: Figure 5. 1dB Compression Point (PA) A3 in formula 3 is usually a negative value, that is, y1(t) decreases as the input signal amplitude increases, a phenomenon called gain compression.The "1dB compression point" is often used in engineering to measure the linear performance of the device. The 1dB compression point is defined as the input signal power P1dB that reduces the gain by 1dB from the linear gain. As shown in Figure 5. According to the definition of 1dB compression point and formula 3, we can get 🔺Two signals at the input.The signal amplified at the input end of the amplifier is generally not a single tone signal, but a spectral signal composed of a certain bandwidth. Due to the nonlinearity of the device, a large number of combined interference frequency components other than the useful signal will be generated at the output end. In addition, the combined frequency components of two or more interfering signals may also cause interference to the useful signal. Have an assumption: Substitute into formula 1, where It can be seen from the above formula that the fundamental frequency components of ω1 and ω2 are generated by the first and third power terms: A total of multiple frequency components are generated: ω1 , ω2 , ω1 ± ω2, 2ω1 - ω2, 2ω2 - ω1 , 3ω1 - 2ω2, 3ω2 - 2ω1.The difference frequency 2ω1 - ω2, 2ω2 - ω1 in the combined frequency is generated by the cubic term. The combination of these two signal frequencies is just within the sideband range of the signal frequency, which may cause interference to adjacent channels, and is one of the main indicators of transmission signal. Figure 6. Intermodulation Signal Interference This interference is caused by the mutual modulation of the two signals, so it is called intermodulation interference. At the same time, it is generated by a cubic term, so it is also called third-order intermodulation interference in engineering.When the third-order intermodulation interference is an important indicator of the communication machine, it is often measured by the intermodulation distortion ratio IMR and the third-order intermodulation blocking point IP3 in engineering. IMR is defined as the ratio of the amplitude of the third-order intermodulation product to the amplitude of the fundamental signal at a certain input amplitude. Definition of IP3: When the third-order intermodulation component increases to be equal to the fundamental frequency component, the receiver cannot receive normally, so there is a . Figure 7. Third-order Intermodulation Blocking Point 🔺Sideband Signals Figure 8. Sideband Signals and the Spectrum In fact, most of the sideband signals are generated outside the bandwidth after the useful signals of different frequencies within the bandwidth are modulated with each other. That is, the sideband signal rises faster than the in-band signal, and the spectral mask in the above figure becomes more and more flat. The increase of sideband signals will cause interference to adjacent channels, so the IEEE 802.11 protocol has strict requirements on the spectrum template, as shown in the Figure 9. Figure 9. DSSS Signal Modulation Spectral Mask Figure 10. OFDM 20MHz Bandwidth Signal Spectral Mask For the power amplifier, its nonlinear characteristics will increase the sideband of the modulated signal, and the sideband amplitude is not easily suppressed by other networks such as filters, and it is easy to cause design difficulties. Therefore, when choosing a PA, not only should pay attention to the maximum linear output that it can achieve, but also whether it can meet the sideband spectrum requirements at this output power.🔺Other Effects of NonlinearityIn addition to the previously mentioned gain drop, which generates a large number of harmonic components, as well as third-order intermodulation and sidebands, nonlinearity can also cause signal and EVM to deteriorate, etc. Ⅴ FAQ 1. What is RF power amplifier?A radio frequency power amplifier (RF power amplifier) is a type of electronic amplifier that converts a low-power radio-frequency signal into a higher power signal. 2. How does RF power amplifier work?An RF amplifier is actually a tuned amplifier that enables the input signal of broadcast or transmitted information to control an output signal. The RF amplifier uses frequency-determining networks to convert the input signal into an output signal that will provide the required response at a given frequency. 3. What is the most efficient class of RF power amplifier?Class C AmplifierThe Class C Amplifier design has the greatest efficiency but the poorest linearity of the classes of amplifiers mentioned here. The previous classes, A, B and AB are considered linear amplifiers, as the output signals amplitude and phase are linearly related to the input signals amplitude and phase. 4. How do I choose an RF power amplifier?Considerations When Choosing An RF Power Amplifier:Gain.Operating Frequency.Output Power Level.Efficiency.Linearity.Mismatch Tolerance.Noise Level. 5. What are the advantages of RF amplifier?Following are the RF Amplifier advantages:The RF amplifier offers greater gain i.e. better sensitivity. It offers better selectivity and hence it has ability to select wanted signals from multiple input signals at the RF receiver. 6. What are the different types of RF amplifiers?Amplifier TypesBroadband AmplifiersGain Block AmplifiersLog AmplifiersVariable Gain AmplifiersLow Noise AmplifiersCoaxial and Waveguide Power AmplifiersLinear AmplifiersBi-Directional Amplifiers 7. What is RF amplifier circuit?A radio frequency power amplifier (RF power amplifier) is a type of electronic circuit that converts a low-power radio-frequency signal into a higher power signal. 8. Is Class D amplifier better than a class AB?The most common audio power amplifier operates in the Class-AB mode. It provides the greatest amount of output power with the least amount of distortion. ... Class-D amplifiers are switches that are more efficient and produce less heat than their Class-AB equivalents. 9. What are RF amplifiers used for?Whenever people need to magnify a radio frequency signal into a higher power signal, the RF amplifier plays a pivotal role. They are used in commercial and defense avionics, space and deep space, electronic warfare, naval applications, mobile internet, satellite communication, and wireless communications. 10. Which amplifier is used in RF amplifier?RF power amplifiers using LDMOS (laterally diffused MOSFET) are the most widely used power semiconductor devices in wireless telecommunication networks, particularly mobile networks. LDMOS-based RF power amplifiers are widely used in digital mobile networks such as 2G, 3G, and 4G.
Ivy On 2022-02-16
Introduction Everyone has heard of FPGA more or less, such as Bitcoin mining, or Microsoft said before that it will use FPGA instead of CPU in the data center. So what exactly is it? Why use it? Compared with CPU, GPU, and ASIC, what are the characteristics of FPGA? FPGA is a chip that can reconfigure circuits and is a hardware reconfigurable architecture. Through programming, users can change its application scenarios at any time, and it can simulate various parallel operations of hardware such as CPU and GPU. By interconnecting with the high-speed interface of the target hardware, the FPGA can complete the low-efficiency part of the target hardware, thereby achieving acceleration at the system level. What Is an FPGA? Catalog Introduction Ⅰ FPGA vs CPU vs GPU vs ASIC Ⅱ Five Advantages of FPGA 2.1 Performance 2.2 Time-to-Market 2.3 Cost 2.4 Stability 2.5 Long-Term Maintenance Ⅲ New Applications of FPGA Ⅳ Development Trend of FPGA Ⅴ FAQ Ⅰ FPGA vs CPU vs GPU vs ASIC The core difference between FPGA and CPU, GPU, ASIC chips, etc. is that the connection and logic layout of the underlying operation unit are not solidified. Users can program the logic unit and switch array through EDA software to configure the function, so as to realize the integration of specific functions.FPGA appears as a semi-custom circuit in the field of application-specific integrated circuits (ASIC), which not only solves the shortcomings of custom circuits, but also improves the limited number of original programmable device gate circuits. Compared with ASIC chips, an important feature of FPGA is its programmable characteristics, that is, the user can specify the FPGA to realize a specific digital circuit through the program. Furthermore, FPGA chips are one of the best choices for small batch systems to improve system integration and reliability. Figure 1. FPGA Basic Structure So why is FPGA so fast? This is all because the computer's CPU(central processing unit) and GPU(graphics processing unit) belong to the von Neumann structure, with instruction decoding and execution, and shared memory. FPGAs, on the other hand, are instruction-free and memory-free architectures that make FPGA chips much more energy-efficient than CPUs or even GPUs. Figure 2. Von Neumann Structure In the von Neumann architecture, since the execution unit (such as the CPU core) may execute any instruction, so an instruction memory, a decoder, an operator of various instructions, and branch and jump processing logic are required. Due to the complex control logic of the instruction stream, it is impossible to have too many independent instruction streams. Therefore, the GPU uses SIMD (single instruction, multiple data) to allow multiple execution units to process different data at the same pace, and the CPU also supports SIMD instruction. The function of each logic unit of the FPGA has been determined during reprogramming, and no instructions are required. Figure 3. Computer CPU If the GPU is used for acceleration, in order to fully utilize the GPU computing, the batch size cannot be too small, and the delay will be on the order of milliseconds. Using FPGA to accelerate, only microsecond-level PCle delay is required. Why is FPGA so much lower latency than GPU? This is basically an architectural difference. FPGAs have both pipeline parallelism and data parallelism, while GPUs have almost only data parallelism (with limited pipeline depth).For example, FPGA chips can change the running hardware design on the chip every few seconds, while chips such as CPU and ASIC are already solidified when they leave the factory and cannot be changed. If ASIC, CPU, GPU, etc. are built buildings, and the routes of rooms, corridors, and stairs in the building have been fixed, while the interior of FPGA is similar to the magic staircase in Hogwarts, which can change the route of room to room at any time. In addition, FPGA does not need to compile the instruction system at the software application level like CPU and GPU. To program FPGA, use hardware description language, and directly compile and burn it into a combination of transistor circuits, that is, directly use transistor circuits to implement user algorithms.The biggest feature of FPGA is its flexibility. It can realize any digital circuit you want and can customize various circuits. Reduce the shackles of special chips, truly tailor-made for your own products, you can flexibly change the design during the design process, and have field programmability, so it is especially suitable for applications that require continuous changes in physical operation logic, such as AI algorithm optimization, data center applications, etc. Architecture Throughput(int ops) Delay Flexibility CPU ~1T N/A Very High GPU ~10T ~1ms High FPGA(Stratix V) ~1T ~1us High FPGA(Stratix 10) ~10T ~1us High ASIC ~10T ~1us Low The FPGA is set up by the RAM stored on the chip to reset its working state, so the on-chip RAM needs to be programmed when working. Users can use different programming methods according to different configuration modes, which can be said to be very flexible and convenient. The FPGA has the following configuration modes:🔺Parallel Mode: Parallel PROM, Flash configures FPGA.🔺Master-Slave Mode: One PROM configures multiple FPGAs.🔺Serial Mode: Serial PROM configures FPGA.🔺Peripheral Mode: The FPGA is used as a peripheral of the microprocessor and programmed by the microprocessor. Computational performance compared with CPU: For example, Stratix series FPGAs perform integer multiplication operations, and their performance is equivalent to that of a 20-core CPU, and for floating-point multiplication operations, their performance is equivalent to an 8-core CPU.Computational performance compared with GPU: FPGA performs integer multiplication and floating-point multiplication operations. There is an order of magnitude difference in performance compared to GPU. The computing performance of GPU can be approached by configuring multipliers and floating-point operation components. Figure 4. CPU and GPU Architecture Diagram The core advantage of FPGA for performing computation-intensive tasks: tasks such as search engine sorting and image processing have strict requirements on the return time limit of results, and it is necessary to reduce the delay of computing steps. Under the traditional GPU acceleration scheme, the data packet size is large, and the delay can reach the millisecond level. Under the FPGA acceleration scheme, the PCIe latency can be reduced to the microsecond level. Driven by long-term technology, the data transmission delay between CPU and FPGA can be reduced to less than 100 nanoseconds.The FPGA can build the same number of pipelines (pipeline parallel structure) for the number of data packet steps, and the data packets can be output immediately after being processed by multiple pipelines. The GPU data parallel mode relies on different data units to process different data packets, and the data units need to be input and output consistently. For stream computing tasks, the FPGA pipeline parallel structure has a natural advantage in latency. FPGA is used to process communication-intensive tasks and is not limited by network cards. It outperforms CPU solutions in terms of packet throughput and delay, and has strong delay stability. Therefore, FPGAs have obvious advantages over CPUs when performing large data processing tasks with high repetition rates.By programming the FPGA, the user can change the internal connection structure of the chip at any time to realize any logic function. Especially in industries with immature technical standards or rapid development and change, FPGA can effectively help enterprises reduce investment risks and sunk costs, and is a functional and economical choice. Figure 5. Computer GPU With the evolution of intelligent market demand, highly customized chips (ASIC SoC) have led to a sharp increase in market risks due to the large scale of non-repetitive investment and long R&D cycle. Relatively speaking, FPGA has advantages in the field of parallel computing tasks, and can replace some ASICs in the field of high performance and multi-channel. The demand for multi-channel computing tasks in the field of artificial intelligence (AI) drives the evolution of FPGA technology to the mainstream. Figure 6. ASIC SoC Ⅱ Five Advantages of FPGA 2.1 Performance Taking advantage of hardware parallelism, FPGAs break the sequential execution model and complete more processing tasks per clock cycle, surpassing the computing power of digital signal processors (DSPs). BDTI(Big Data Test Infrastructure), a well-known analysis and benchmarking company, has published benchmarks that show that in some applications, FPGAs can handle many times more processing power per dollar than DSP solutions. Controlling input and output (I/O) at the hardware level provides faster response times and specialized functionality to meet application needs. 2.2 Time-to-Market Despite increasing time-to-market constraints, FPGA technology offers flexibility and the ability to rapidly prototype. Users can test an idea or concept and complete verification in hardware without going through the lengthy manufacturing process of custom ASIC design. This allows users to make incremental modifications and iterate FPGA designs in hours, saving weeks. Commercial off-the-shelf (COTS) hardware provides different types of I/O connected to user-programmable FPGA chips. The increasing popularity of high-level software tools reduces the learning curve and abstraction layers, and often provides useful IP cores (pre-built functions) for advanced control and signal processing. 2.3 Cost The non-recurring engineering (NRE) cost of custom ASIC design far exceeds the cost of FPGA-based hardware solutions. The huge initial investment in ASIC design shows that OEMs need to ship thousands of chips each year, but more end users need custom hardware capabilities that enable the development of tens to hundreds of systems. The nature of programmable chips means that users can save on manufacturing costs as well as long lead times for assembly. System requirements change from time to time, but the cost of changing the FPGA design is negligible compared to ASCI's huge expense. 2.4 Stability Software tools provide the programming environment, and FPGA circuits are the real "hard" implementation of programming. Processor-based systems often contain multiple layers of abstraction that can schedule tasks and share resources among multiple processes. The driver layer controls hardware resources, while the operating system manages memory and processor bandwidth. For any given processor core, only one instruction can be executed at a time, and processor-based systems face the risk of tightly time-bound tasks taking over each other at all times. FPGAs, on the other hand, do not use an operating system, and have true parallel execution and deterministic hardware that focuses on each task, reducing the chance of stability issues. 2.5 Long-Term Maintenance As mentioned above, FPGA chips are field-upgradable without the time and expense involved in redesigning ASICs. For example, digital communication protocols contain specifications that can change over time, and ASIC-based interfaces can create maintenance and forward compatibility difficulties. Reconfigurable FPGA chips can accommodate future modifications. As a product or system matures, users can enhance functionality without spending time redesigning hardware or modifying board layouts. Ⅲ New Applications of FPGA At present, the FPGAs mainly produced by Xilinx and Altera with the highest market share, which are all based on SRAM technology, and need to be connected to an external memory to save the program when in use. When powered on, the FPGA reads the data in the external memory into the on-chip RAM, and after completing the configuration, it enters the working state. When power off, the FPGA returns to a white chip, and the internal logic disappears. In this way, the FPGA can not only be used repeatedly, but also does not require a special programmer, but only a general EPROM and PROM programmer. So Actel, QuickLogic and other companies also provide FPGAs with anti-fuse technology, which can only be downloaded once. They have the advantages of anti-radiation, high & low temperature resistance, low power consumption and fast speed. They are widely used in military and aerospace fields. FPGA cannot be erased and written repeatedly, which is troublesome and expensive in the early stage of development. Lattice is the inventor of ISP technology, which has certain characteristics in small-scale PLD applications. Early Xilinx products generally did not involve military and aerospace markets, but now a number of products such as Q Pro-R have entered such fields.In the industrial field, FPGA chips are widely used in the industrial field, and are widely used in video processing, image processing, CNC machine tools and other fields to realize signal control and operation acceleration functions. With the development of intelligence and automation technology, the industrial field is gradually shifting from human resources as the core element to intelligent unmanned factories with automation as the core element.Smart electric vehicles will be the mainstream development direction of the automotive industry in the future. At present, the application of FPGA in automotive cameras and sensors is relatively mature. In the artificial intelligence system of automatic/intelligent driving vehicles, the applicability of FPGA will be the most suitable for processing sophisticated ADAS and autonomous driving. Figure 7. FPGA for Auto In the field of automotive electronic system interface and control, FPGA chips are used to control and drive electric vehicle motor control systems, connect various in-vehicle equipment such as driving systems, instrument panels, radar, ultrasonic sensors, etc. control. In the field of video bridging and fusion, FPGA chips can be used to realize functions such as signal bridging of multiple image sensors, 3D surround view video fusion, reversing auxiliary video, and assisted driving video.In the field of communication, the number of 5G base stations has increased, and the FPGA usage of a single base station has increased, driving the increase in FPGA demand. According to estimates, the FPGA consumption of a 5G single base station is expected to increase from 1-3 blocks in the 4G period to 4-5 blocks in the 5G period. Figure 8. RFSoC FPGA Board Target 5G eFPGA technology is superior to traditional FPGA solutions in terms of performance, cost, power consumption, profitability, etc., and can provide flexible solutions for different application scenarios and different market segments. The economic trend of increasing design complexity and falling equipment costs has stimulated the market demand for eFPGA technology. Ⅳ Development Trend of FPGA First of all, with the commercialization of the new generation of communication technology, the demand for products such as communication base stations, servers, and intelligent terminals will further expand, thereby driving the increase in the market demand for FPGA chips. At the same time, smart cities, smart factories, and consumer electronics pay more attention to the functionality of various smart IoT devices, which will drive the wide application of FPGA chips in smart IoT devices. With the development of the Internet of Vehicles technology, the scale of the use of FPGA chips in the automotive industry will increase day by day to build a more complete Internet of Vehicles and realize smarter autonomous driving functions. Therefore, with the rapid penetration of 5G, the vigorous development of AI and the increasing trend of automotive intelligence, it is expected that the demand for FPGAs in the three fields of communication, AI and automotive electronics will continue to increase in the future, which will also promote The FPGA industry continues to grow. Ⅴ FAQ 1. What is FPGA and why it is used?The acronym FPGA stands for Field Programmable Gate Array. It is an integrated circuit that can be programmed by a user for a specific use after it has been manufactured. ... These blocks create a physical array of logic gates that can be customized to perform specific computing tasks. 2. Is FPGA faster than GPU?The difference between GPU and FPGA performance is not a static factor, but it does depend on the size of the data set. A study by Sanaullah and Herbordt [7] revealed that FPGA can compute small samples of 3D FFT tens of times faster than GPU. The difference is less clear when the data set gets bigger. 3. Is FPGA faster than CPU?A FPGA can hit the data cell faster and more often than a CPU can do it meaning the FPGA causes more results to occur during an attack. It all goes faster when an FPGA is used. And as a side benefit, no trace of all this is left on the CPU because it's never touched when an FPGA is used. 4. Are FPGAs efficient?Efficiency and Power: FPGAs are well-known for their power efficiency. A research project done by Microsoft on an image classification project showed that Arria 10 FPGA performs almost 10 times better in power consumption. 5. Is FPGA programming hard?FPGA vendors have touted their wares as ideal replacements for DSPs, CPUs, and GPUs – even for all of them in a single device – but they are notoriously difficult for software engineers to program as they are not anything like a conventional processor. 6. What can you do with FPGAs?Uses for FPGAs cover a wide range of areas—from equipment for video and imaging, to circuitry for computer, auto, aerospace, and military applications, in addition to electronics for specialized processing and more. 7. What is the difference between processor and FPGA?Microprocessor vs FPGA: A microprocessor is a simplified CPU or Central Processing Unit. ... An FPGA doesn't have any hardwired logic blocks because that would defeat the field programmable aspect of it. An FPGA is laid out like a net with each junction containing a switch that the user can make or break. 8. What language is used to program FPGA?VerilogTraditionally, FPGAs are programmed using pro-level hardware-description languages such as Verilog or VHDL. 9. How many times can you program an FPGA?There is effectively no limit to the number of times a device can be reconfigured; the configuration is stored in SRAM, which has no write limit. most Fpgas can be passively loaded from a processor, one word at a time. That processor can get the FPGA image from anywhere. 10. What are the advantages of FPGA?FPGA advantagesLong-term availabilityUpdating and adaptation at the customerVery short time-to-marketFast and efficient systemsAcceleration of softwareReal-time applicationsMassively parallel data processing 11. How do you make an FPGA?FPGA design checklistMake sure you have plenty of time to spare.Find a decent computer.If you can afford it, add a big display.Decide which operating system to use.Consider using a virtual machine (VM).Select an FPGA vendor.Pick out a suitable development board.Select an embedded processor to use. 12. What is FPGA for beginners?FPGA stands for Field Programmable Gate Array. As you may already know, FPGA essentially is a huge array of gates that can be programmed and reconfigured any time anywhere. Huge array of gates is an oversimplified description of FPGA. FPGA is indeed much more complex than a simple array of gates. 13. What is FPGA in Verilog?FPGAs are nothing, but reconfigurable logic blocks and interconnects can be programmed by Hardware Description Language like Verilog/ VHDL to perform a specific functionality. 14. Do we need to program the FPGA once powered off?If you have a SRAM-based FPGA, like the Spartan 3, then you have to program it each time it is powered up. The reason for this is that the SRAM which stores the configuration is volatile and loses the programmed configuration after power is switched off. 15. How is FPGA different from microcontroller?One of the main differences between a microcontroller and an FPGA is that an FPGA doesn't have a fixed hardware structure, while a microcontroller does. While FPGAs include fixed logic cells, these, along with the interconnects, can be programmed in parallel by using HDL coding language.
Ivy On 2022-01-26
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