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IntroductionⅠ What is the Backlit Keyboard? 1.1 Advantages of the Backlit Keyboard 1.2 Disadvantages  of the Backlit KeyboardⅡ How to Enable and Disable a Backlit KeyboardⅢ Compact Backlit Keyboard w/Force Sensing Resistor (USB) (Black) | SLK-79-FSR-USB by iKey    3.1 How Does a Force Sensing Resistor (FSR) Work?    3.2 How do Force Sensing Resistors Measure Force?    3.3 How do You Calibrate a Force Sensing Resistor?    3.4 How are Force Sensing Resistors Made?    3.5 Matrix or Single-Point Force Sensing Resistors    3.6 How are Force Sensing Resistors Used?Ⅳ Factors to Consider Before Purchasing a Backlit Keyboard    4.1 Price    4.2 Increased Power Usage    4.3 Brightness    4.4 RGBⅤ How Much does a Backlit Gaming Keyboard Cost?Ⅵ Frequently Asked Questions about Backlit KeyboardIntroductionThe term "backlit keyboard" refers to a keyboard that has a light beneath the keys. In low-light situations, the backlight illuminates the letters and symbols on the keys to make them visible. Because the print on the keys is semi-transparent, the light will pass through it like a window. Read this article to learn how to choose a backlit keyboard quickly.Video: Backlight KeyboardsⅠ What is the Backlit Keyboard?A backlit keyboard, also known as an illuminated keyboard or a backlit gaming keyboard, is one that has lights inside it. The lights illuminate the area behind and around the keys, making them visible in low-light or dark settings. For energy efficiency and increased brightness, the light source is typically made up of mini LED light bulbs. Backlit gaming keyboards are popular among computer gamers, but they can also be used for general computing tasks. G.SKILL 's multicolor backlit gaming keyboard is shown below. 1.1 Advantages of the Backlit KeyboardThe distinction between a backlit keyboard and a regular keyboard is that the backlit keyboards can be used in the dark because they are illuminated from behind the keys.The characters associated with each key on regular boards are simply printed on and do not light up. Backlit keyboards  are therefore the most versatile option.You may have one or more colors depending on the keyboard supplier and model.A colorful backlit keyboard is a way to go for the gamer or the person who wants to add a little flair to their computer hardware setup.While these keyboards do have a more youthful feel to them, they are suitable for anyone who is young at heart.In general, the F and J keys have raised lines on them if you look at your keyboard (you may have to feel your keyboard).It's supposed to help you navigate the board even when the lighting isn't ideal.To work properly, you must, of course, know how to type efficiently and not just with your pointer finger (aka index finger).Some argue that efficient backlighting is the answer.Laptops with lights can be both functional and attractive.Learn more about illuminated keyboards as the ultimate gaming, editing, or programming accessory. 1.2 Disadvantages of the Backlit KeyboardFigure 1 Backlit keyboardThey cost more than other types of keyboards. Most models with key lighting start around $800 and rise from there - sometimes dramatically.Illuminated keyboards use more energy than standard keyboards. It can drain your battery faster if it is not plugged in and charging.Ⅱ How to Enable a Backlit KeyboardTouching the keys or across the edge of the keyboard usually activates the backlit feature. When the keys or keyboard edges are not touched, the lights automatically turn off after a short period of time. Turning off the lights automatically helps to conserve battery energy, extending battery performance between charges.Backlit keyboards for laptops and desktop computers may also include special keys or FN keys for permanently turning the backlight on and off, as well as the ability to change the color. The special or FN key to press on a keyboard varies depending on the manufacturer of the keyboard or laptop.In the Windows Mobility Center, most new PC laptops allow you to change the backlighting on the keyboard. On Dell laptops, this is frequently Fn+F10 or simply F10. Fn+Spacebar is the hidden key for adjusting the backlit keyboard  on Lenovo laptops.Ⅲ Compact Backlit Keyboard w/Force Sensing Resistor (USB) (Black) | SLK-79-FSR-USB by iKeyThe SLK-79-FSR-M keyboard was created for mobile applications that require a small footprint. The SLK-79-FSR-M, which includes an integrated force sensing resistor pointing gadget with dual left-click capability, packs a lot of power into a small package. The SLK-79-FSR-M includes backlit keys for working in low-light environments. The SLK-79-FSR-M, like the other iKey keyboards, has sealed industrial silicone rubber keypads and sturdy ABS polycarbonate cases.Features:12 Keys for FunctionPointing Device With Integrated Force Sensing ResistorKeyboard with Red BacklightConfigurations for USB and PS/2 are available. 3.1 How Does a Force Sensing Resistor (FSR) Work?In recent years, printed, thin, and flexible sensors have created quite a stir in the design engineering community. This is largely due to the proliferation of smart, lightweight, and energy-efficient technologies that have become ingrained in our daily lives. Naturally, when designing these small but powerful devices and products, the embedded components that make them game-changers should share the same characteristics.Force sensing resistors (also known as printed force sensors or force-sensitive resistors) are a large and expanding class of embedded components, with many new sensor types introduced in recent years. Force sensing resistors    , on the other hand, are not a new technology. For decades, force-sensing resistors have been used as an embedded component.3.2 How do Force Sensing Resistors Measure Force?Most engineers know that the formula for force is an object's mass multiplied by its acceleration (or, F=M*A) or applied pressure multiplied by contact zone (F=P*Area). Newtons (N), pound-force (lbf), and other engineering units are used to represent "F" in these equations.Figure 2: When a force sensing resistor is applied, the conductance response as a function of force is linear.Pressure sensor resistors are not pre-calibrated to correlate a force reading to a known technology unit on their own. The force measurement result captured by a force sensing resistor. On the other hand, can be correlated to the applied force via a calibration procedure.Piezoresistive sensing technology is a force-sensing resistor, This means that they are passive elements that serve as variable resistors in an electrical circuit. As illustrated in Figure 1, when the sensor is unloaded, it has a high resistance (on the order of Megaohms (M)) that decreases as force is applied (usually on the order of Kiloohms (K)). When the inverse of resistance (conductance) is considered, the thermal conduction response as a function of force is linear within the sensor's specified force range.3.3 How do You Calibrate a Force Sensing Resistor?Force sensing resistors  can really be calibrated with as few as two-to-three known loads due to their resistance/conductance linear relationship.Furthermore, if the circuit is built with adjustable components, the sensor's sensitivity can indeed be adjusted for optimal performance in the specific force range.3.4 How are Force Sensing Resistors Made?A semi-conductive material – or semi-conductive ink – is sandwiched between two thin substrates to form force-sensing resistors. As illustrated in Figure 3, there are two types of force sensing resistor technologies: Shunt Mode and Thru Mode.Figure 3:  The differences between shunt and thru mode force sensing resistor technologies.Force sensing resistors  in the shunt mode are polymer thick-film devices made up of two membranes separated by a thin air gap. One membrane contains two sets of interdigitated traces that are electronically isolated from one another, while the other is coated with a special textured, resistive ink.Thru mode force-sensing resistors  are flexible printed circuits with two outer substrates of polyester film. Above and below a pressure-sensitive layer, silver circles with traces are positioned, followed by a conductive polymer. The two layers of the substrate are laminated together with an adhesive layer. 3.5 Matrix or Single-Point Force Sensing ResistorsFigure 4: Examples of different force sensitive resistor technologies.ForceSensing resistors  can be configured as single-point force sensors or as a matrix array to capture pressure distribution over a large area. Pressure mapping technology refers to the use of force-sensing resistor  matrices.Tekscan's FlexiForceTM sensors are a type of thru mode force-sensing resistor. This technology's flexibility, combined with its operating capabilities and ability to operate on simple circuitry, makes it an excellent choice for embedding into smart devices with limited space and power. FlexiForce sensors are also extremely adaptable. Size, shape,  electrical termination, electrical termination, sensitivity,  and operating temperature can all be customized to meet the needs of your application. 3.6 How are Force Sensing Resistors Used?While there are new applications for force-sensing resistor technology every day, the majority of them fall into one of four categories:Detecting or measuring the rate at which a force changes.Detecting or measuring a change in force relative to another object.Touch and/or contact detectionDetecting force thresholds to initiate some kind of action (e.g., IoT applications)This short video gives you a better visual understanding of the various applications for force sensing resistors, specifically FlexiForce force sensing resistors.Are you interested in purchasing force sensing resistors? Ⅳ Factors to Consider Before Purchasing a Backlit KeyboardBefore purchasing a system with a backlit keyboard, you should think about a few things. The following sections go over each of them:4.1 PriceBacklit keyboard laptops are significantly more expensive than those without. As a result, it is recommended that you only invest in a feature if you are certain that it will benefit you and improve your user experience. It is recommended that you skip this feature if you rarely use your computer in dimly lit environments or if you can type without looking. 4.2 Increased Power UsageYour battery  percentage will quickly be depleted by backlit keyboard  s. As a result, if you value durability over aesthetics, you should avoid purchasing a laptop with a backlit keyboard,  However, if you don't mind having your system plugged in the majority of the time, the reduced battery  life shouldn't be a big deal. Furthermore, if you purchase a laptop with a backlit keyboard.  you can turn the feature on or off according to your needs.4.3  BrightnessOne of the main benefits of purchasing a laptop with a backlit keyboard  is the ability to use your system effectively in dimly lit environments. As a result, you should make sure that the backlit keyboard on your laptop is bright enough to meet your needs.4.4  RGBIf you're convinced that a backlit keyboard is a must-have feature for your ideal laptop, then go for the best that the market has to offer. When purchasing a laptop with a backlit keyboard, make sure that the keyboard can switch between different color ranges to effectively adapt to your surroundings.Ⅴ How Much does a Backlit Gaming Keyboard Cost?Gaming keyboards with backlighting are more expensive than standard keyboards, costing around $90 or more. They come in both wired and wireless versions. Wireless models require batteries to operate and may include a USB cable for charging the batteries by plugging the keyboard into the computer.Backlit gaming keyboards are made by a variety of companies, the most popular of which are Corsair, G.SKILL, Logitech, and RAZER.Ⅵ Frequently Asked Questions about Backlit Keyboard6.1 Are there wireless backlit keyboards?These keyboards are wireless and have backlit keys together. ... With backlit keys you are able to work in dark or dim light surroundings whereas wireless connectivity allows you to get free of all wires. Wireless keyboards mostly use bluetooth and are battery powered.6.2 Does backlit keyboard drain battery?Powering the keyboard backlights is a lesser drain on the battery, but there's a built-in setting that I recently learned about that turns off the keyboard backlights after a period of inactivity too.6.3 Does LED keyboard consume more power?There is no difference between the amount of energy/electricity usage a light up/LED keyboard will use compared to a non-light/non-LED up keyboard.6.4 Can you buy a backlit keyboard?Keyboards do come in a variety of different sizes, configurations, and builds, but these don't influence whether the keyboard has a backlight. Both membrane keyboards and mechanical keyboards may be built with backlights. Also, backlights are integrated into both desktop keyboards and laptop keyboards.6.5 Does Microsoft make a backlit keyboard?Yes, it does!all Surface Laptop 3 models come with the same three levels of the backlit keyboard. You can control the backlit on the Surface Laptop 3 keyboard by pressing the F1 media key (Next to Esc key). 1st Press: Activate backlight at level 1 (min). 2nd Press: Activate backlight at level 2 (medium).6.6 Does the surface laptop 2 have a backlit keyboard?Surface Laptop 2 keyboard and trackpadThe Surface Laptop 2 features a full-sized chicklet style keyboard with 1.5 mm of travel (versus 1.3 mm in Surface Pro 6) and three-stages of backlighting.6.7 Does HP laptop have backlit keyboard?Many HP laptops have backlit keyboards, some just a single color, others with what's known as RGB lighting, that can be customized to show different colors.6.8 Does ASUS have backlit keyboard?Here you can learn more about ASUS keyboard hotkeys introduction. For part of Notebook models, backlit function key is F3 and F4 key . If they are available, they can enable the backlit by pressing FN and F4 keys (FN+F4 keys) at the same time. ... For Gaming Notebook models, it's generally on Up and Down keys.6.9 How do I make my laptop keyboard glow?Also, depending on your computer model, your PC may be configured to control the backlit keyboard via the F9 or F11 button rather than the F5 button. Practice the same simultaneous Fn + F11 operation to turn on a backlight keyboard light.

Executive Summary: What is a Phototransistor?A phototransistor is a light-sensitive semiconductor device that converts incident light into electric current while providing internal gain amplification. Unlike simple photodiodes, phototransistors utilize a bipolar junction structure (NPN or PNP) to amplify the signal, making them highly effective for optical switching, object detection, and encoding systems in modern 2026 electronics.Ⅰ Introduction to PhototransistorsThe phototransistor is a specialized semiconductor device engineered to detect light levels and modulate the current flowing between the emitter and collector based on the photon intensity it receives.While both phototransistors and photodiodes serve as optical sensors, the phototransistor distinguishes itself through high sensitivity attributed to the internal gain of its bipolar transistor architecture. As of 2026, this intrinsic amplification makes phototransistors the preferred choice for applications requiring robust signal detection without complex external amplification circuitry.Ⅱ Video Tutorial: How Phototransistors WorkVisual learners can understand the practical operation of light detection in the following tutorial.Phototransistor Tutorial Phototransistor Video Description:A comprehensive tutorial demonstrating how to utilize phototransistors for precise light detection in circuit design.  Ⅲ What Is a Phototransistor?A phototransistor is an electronic switching and current amplification component that operates by converting photon energy into electrical signals. When light strikes the exposed base-collector junction, a reverse current flows proportional to the luminance intensity.Widely used to convert light pulses into digital electrical signals, these components are powered by light interactions rather than solely electrical bias at the base. They offer high gain and low cost, making them ubiquitous in 2026 consumer electronics. Figure 1: Phototransistor SymbolFunctionally, phototransistors share similarities with photoresistors (LDRs), but with a key distinction: phototransistors generate current and voltage through the photovoltaic effect and amplification, whereas LDRs only change resistance.Transistors with the base terminal exposed are chemically doped to maximize light sensitivity. Photons striking the depletion layer generate electron-hole pairs, activating the transistor just as a base current would in a standard BJT. Silicon-based photosensors typically respond to visible and near-infrared radiation (approx. 400nm to 1100nm). Ⅳ How are Phototransistors Constructed?The phototransistor's structure is specifically optimized for photo-applications by maximizing the area of the base-collector junction. While ordinary bipolar transistors exhibit some photosensitivity, phototransistors feature significantly larger base and collector areas to capture maximum light flux.Figure 2: Construction of a PhototransistorⅤ Semiconductor Material EvolutionHistorical phototransistors utilized a homo-junction structure, fabricated entirely from germanium or silicon. In contrast, modern 2026 phototransistors often employ type III-V semiconductor materials, such as gallium arsenide (GaAs), to target specific wavelengths and increase efficiency.Key structural variations include:NPN Topology: The most popular configuration due to the higher mobility of electrons compared to holes.Heterostructures: Utilizing different materials on either side of the PN junction to enhance conversion efficiency.Mesa Structure: A common physical layout for optimized light absorption.Schottky Junctions: Occasionally used for the collector to improve switching speeds.To ensure optimal sensitivity, the emitter contact is frequently offset, preventing it from blocking light from reaching the active region. Ⅵ How Does a Phototransistor Work?A phototransistor operates by using light to control the flow of current, effectively replacing the base current of a standard transistor with photon energy.Biasing: The collector is biased positively relative to the emitter (in NPN), creating a reverse-biased Base-Collector (B-C) junction.Injection: Light strikes the B-C junction, generating electron-hole pairs.Amplification: The movement of these carriers constitutes a base current, which the transistor amplifies by its gain factor (hFE).Typically, the physical base terminal is left unconnected (floating), as the device is controlled entirely by incident light. Ⅶ Key Electrical CharacteristicsSince phototransistors are essentially Bipolar NPN Transistors with an exposed junction, their V-I characteristics resemble a standard BJT family of curves, but with Light Intensity (mW/cm²) replacing Base Current (IB).Dark Current: When no light is present, a minuscule leakage current flows from collector to emitter. In high-precision applications, minimizing this Dark Current is crucial.Light Current: As light intensity increases, the base current rises, triggering the amplification process. Figure 3: Reverse Bias Configuration The collector current characteristics curve below demonstrates the linear relationship between light intensity and output current in the active region.Figure 4: Collector Current vs. Irradiance Ⅷ Selection Criteria & PropertiesWhen selecting a component for 2026 designs, engineers must evaluate specific properties to ensure the device matches the optical environment.Critical Datasheet Properties:Peak Wavelength: The specific color of light (e.g., 850nm IR vs. 560nm Visible) the device is most sensitive to.Linearity: How accurately the output follows the input light intensity.Sensitivity: The ratio of output current to incident light power.Response Time: The rise and fall time, which determines the maximum data rate (typically slower than photodiodes).Acceptance Angle: The field of view from which the sensor can detect light. Ⅸ Common Types: BJT vs. FETPhototransistors are primarily categorized by their internal transistor architecture:BJT Phototransistor: The standard type. In darkness, it leaks only ~100 nA. Under illumination, it can conduct up to 50mA. This high current handling capability distinguishes it from photodiodes.Photo-FET (Field Effect Transistor): Utilizes light to generate a gate voltage that controls the drain-source current. Photo-FETs offer extremely high input impedance and are more sensitive to weak light signals, though they are less common in general switching applications. Ⅹ Practical Circuit Examples (2026 Applications)The primary goal of phototransistor circuits is to generate a usable output voltage from light-induced current. Unlike photodiodes which often require Transimpedance Amplifiers (TIA), phototransistors have built-in gain, allowing for simpler circuit designs.Common Configurations:Common-Emitter (Inverting): Output voltage drops as light increases.Common-Collector (Non-Inverting): Output voltage rises as light increases.Figure 5: Basic Amplifier Configurations 10.1 Step-by-Step Circuit Implementations 1. Light Operated Relay (Automatic Day Switch)Mechanism: When light strikes phototransistor Q1, it conducts, supplying base current to the driver transistor Q2. Q2 then activates the mechanical relay, turning on the connected load. 2. Darkness Operated Relay (Night Light)Mechanism: By inverting the logic, the relay activates only when light is absent. In darkness, the phototransistor turns off (high resistance), allowing the bias resistor to trigger Q2. 3. Light Interruption Alarm (Security System)Mechanism: This circuit functions as a tripwire. Under normal conditions (laser/light hitting sensor), the phototransistor pulls the SCR gate LOW (off). When the beam is broken by an intruder, the gate voltage rises, latching the SCR and sounding the alarm until manually reset. Ⅺ Datasheet Specifications to WatchTo ensure system reliability, consult the following parameters in manufacturer datasheets:Collector Current (IC): Maximum current the device can handle (typically 1mA - 50mA).Dark Current (ID): Leakage current in total darkness (lower is better for precision).Peak Wavelength (λp): The wavelength of maximum sensitivity.VCE(sat): Collector-Emitter saturation voltage.Rise/Fall Time (tr/tf): Critical for optical data transmission applications.Power Dissipation (Ptot): Thermal limits of the package. ⅻ Pros and Cons AnalysisSelecting the right optical sensor requires balancing sensitivity, speed, and cost.AdvantagesDisadvantagesHigh Gain: Produces higher current output than photodiodes, reducing the need for external amplifiers.Limited Voltage: Cannot withstand high voltages compared to Thyristors or Triacs.Cost-Effective: Inexpensive to manufacture and integrate into ICs.Slower Speed: Slower response time (lower bandwidth) compared to PIN photodiodes.Simplicity: Can drive small relays or logic gates directly in simple circuits.Temperature Sensitivity: Dark current increases significantly with temperature fluctuations. XIII Modern Applications in 2026Due to their versatility, phototransistors are integral to many modern technologies:Optocouplers (Optoisolators): Protecting low-voltage logic circuits from high-voltage spikes in power supplies.Optical Encoders: Used in robotics and motors to detect position and speed.Object Detection: Proximity sensors in smartphones and automated manufacturing lines.Safety Systems: Smoke detectors and light curtain barriers for industrial machinery.Remote Control Receivers: IR detection for consumer electronics (though often integrated with demodulators). XIV Comparison: Photodiode vs. PhototransistorWhile both detect light, their use cases differ based on speed and sensitivity needs.FeaturePhotodiodePhototransistorOutputLow Current (µA)High Current (mA) - AmplifiedResponse SpeedVery Fast (Nanoseconds)Moderate (Microseconds)ApplicationsFiber Optics, High-Speed DataRemote Controls, Light Switches, EncodersNoiseLow NoiseHigher Noise levels XV Frequently Asked Questions1. What type of device is a phototransistor?A phototransistor is a bipolar semiconductor device. It functions as a transistor where the base current is generated by incident photons striking the exposed semiconductor junction, rather than an electrical connection.2. What is the main difference between a standard transistor and a phototransistor?Physically, the primary difference is the packaging. A phototransistor has a transparent lens or window to allow light to reach the junction, and it often lacks an external base pin. Electrically, it is controlled by light intensity rather than input current.3. Is a phototransistor considered a sensor?Yes, it is a discrete photosensor. It detects the presence and intensity of light and converts it into a measurable electrical signal.4. How do you test if a phototransistor is working?You can test it using a multimeter or a simple circuit:Connect the phototransistor in series with a resistor and LED to a power source (checking polarity).Expose the sensor to light; the LED should brighten.Cover the sensor; the LED should dim or turn off.5. Which is better: Photodiode or Phototransistor?Neither is universally "better"; it depends on the application. For high-speed data (like fiber optics), a photodiode is superior. For switching and sensing without extra amplifiers, a phototransistor is more efficient due to its internal gain.{ "@context": "https://schema.org", "@graph": [ { "@type": "Article", "headline": "Phototransistors: The Ultimate 2026 Guide", "datePublished": "2021-12-02", "dateModified": "2026-01-07", "description": "A comprehensive guide to phototransistors, covering construction, working principles, circuit diagrams, and 2026 applications.", "image": "https://www.kynix.com/editor_u/image/20211202/2021120216390176.jpg", "author": { "@type": "Organization", "name": "Kynix Electronics" } }, { "@type": "FAQPage", "mainEntity": [ { "@type": "Question", "name": "What type of device is a phototransistor?", "acceptedAnswer": { "@type": "Answer", "text": "A phototransistor is a bipolar semiconductor device where the base current is generated by incident photons striking the exposed junction." } }, { "@type": "Question", "name": "What is the difference between a transistor and a phototransistor?", "acceptedAnswer": { "@type": "Answer", "text": "The main difference is that a phototransistor has an exposed optical window and is controlled by light intensity, whereas a standard transistor is controlled by electrical current at the base pin." } }, { "@type": "Question", "name": "Is a phototransistor a sensor?", "acceptedAnswer": { "@type": "Answer", "text": "Yes, a phototransistor is a discrete photosensor that converts light intensity into an electrical signal." } }, { "@type": "Question", "name": "Which is better: Photodiode or Phototransistor?", "acceptedAnswer": { "@type": "Answer", "text": "Photodiodes are better for high-speed data applications, while phototransistors are better for switching and sensing applications requiring higher sensitivity and gain." } } ] }, { "@type": "HowTo", "name": "How to Build a Simple Light Interruption Alarm", "step": [ { "@type": "HowToStep", "name": "Setup the Phototransistor", "text": "Connect the phototransistor to a pull-down resistor to create a voltage divider." }, { "@type": "HowToStep", "name": "Connect the SCR", "text": "Connect the output of the phototransistor junction to the Gate of an SCR (Silicon Controlled Rectifier)." }, { "@type": "HowToStep", "name": "Align the Light Source", "text": "Point a laser or light beam directly at the phototransistor. This keeps the SCR gate low (Off)." }, { "@type": "HowToStep", "name": "Trigger the Alarm", "text": "Interrupt the light beam. The phototransistor turns off, voltage spikes at the SCR gate, latching the alarm on." } ] } ]}

2026 Executive Summary: Reading SMD Resistor CodesHow do you read SMD resistor codes? For standard 3-digit codes, the first two numbers are significant digits, and the third is the multiplier (10^x). For 4-digit codes (precision), the first three are significant. The EIA-96 system uses a two-digit code and a letter multiplier. This authoritative guide covers all calculation methods, updated for 2026 industry standards.What are SMD Resistors? (2026 Overview)SMD Resistor, also known as a Chip Resistor, is a surface-mount passive component essential for modern high-density electronics. Manufactured by sintering metal powder and glass glaze on a ceramic substrate, these components offer superior resistance to humidity, high temperatures, and vibration compared to legacy through-hole parts. As of 2026, they are the industry standard for everything from AI hardware to smartphones. While different resistors feature varied specifications, the critical question remains: how are these microscopic resistance values marked and decoded? Figure 1. Structure of SMD ResistorsⅠ How to Read Resistor Markings: 4 Key MethodsTo master resistor identification, one must understand the four global standards used to denote resistance values. These methods are governed by IEC 60062 standards:1. Direct Marking MethodThis method prints the actual numbers and unit symbols directly on the resistor surface. The allowable error (tolerance) is expressed as a percentage. If no deviation is marked, the standard tolerance is typically ±20%.2. Text Symbol MethodThis approach uses a combination of Arabic numerals and text symbols to indicate the nominal resistance and tolerance. The number preceding the symbol represents the integer value, while the number following represents the decimal. Tolerance characters are standardized: D (±0.5%), F (±1%), G (±2%), J (±5%), K (±10%), M (±20%).3. Digital Method (Most Common for SMD)This method uses a 3-digit or 4-digit code. Read from left to right, the initial digits represent the significant figures (effective values), and the final digit is the exponent (multiplier), indicating the number of zeros to add. The unit is always Ohms (Ω).4. Color Code Marking MethodWhile rare on modern SMDs (except MELF packages), color bands are the standard for through-hole resistors. The bands represent values and multipliers:Black (0), Brown (1), Red (2), Orange (3), Yellow (4)Green (5), Blue (6), Violet (7), Gray (8), White (9)Tolerance: Gold (±5%), Silver (±10%), Colorless (±20%)Figure 2. Universal Resistor Color Code DiagramReading Tip: For a four-band resistor, the last band (usually gold/silver) is the tolerance. The first two bands are digits, and the third is the multiplier. For five-band precision resistors, the first three are digits, the fourth is the multiplier, and the fifth is the tolerance. Ⅱ Calculating SMD Resistor Values (Step-by-Step)2.1 Understanding Character Code MarkingsVideo: SMD Resistor Coding ExplainedMarking chip resistors requires a compact system due to the component's microscopic size. While large packages may use full numbers, 0603, 0805, and 1206 packages use coded systems. Here is the 2026 standard breakdown for decoding these values:The 3-Digit System (Standard Tolerance ±5%):1. The first and second digits represent the significant resistance figures.2. The third digit is the multiplier (10^x).Decoding Guide by Third Digit:• Ends in 0: No extra zeros. Example: 100 = 10 Ω.• Ends in 1: Add one zero (x10). Example: 101 = 100 Ω.• Ends in 2: Add two zeros (x100). Example: 102 = 1,000 Ω (1 kΩ).• Ends in 3: Add three zeros (x1,000). Example: 103 = 10,000 Ω (10 kΩ).• Ends in 4: Add four zeros. Example: 104 = 100 kΩ.• Ends in 5: Add five zeros. Example: 105 = 1 MΩ.• Ends in 6: Add six zeros. Example: 106 = 10 MΩ.The 4-Digit System (Precision Tolerance ±1%):For higher precision, three significant digits are used. Example: 1001 means 100 + one zero = 1000 Ω (1 kΩ).Note: Ultra-small packages like 01005, 0201, and 0402 are physically too small for markings. These must be measured with a multimeter or tracked via reel tape labeling.2.2 Real-World Calculation ExamplesCase 1: 3-Digit Code (±5% Tolerance)This uses two significant digits followed by a multiplier.Calculation: 153 → 15 followed by 3 zeros → 15,000 Ω = 15 kΩDecimal Values: "R" represents the decimal point. Code 6R8 → 6.8 ΩCase 2: 4-Digit Code (±1% Tolerance)Common on packages like 0805, 1206, and 2512. The first three digits are significant.Calculation: 2372 → 237 followed by 2 zeros → 23,700 Ω = 23.7 kΩDecimal Values: 3R24 → 3.24 ΩCase 3: EIA-96 System (The "Cryptic" Code)Used for 1% tolerance resistors on small 0603 packages where 4 digits won't fit. This system uses a two-digit code (referencing a lookup table) and a letter multiplier.Format: [Code] [Letter]Example Multipliers: Y=0.01, X=0.1, A=1, B=10, C=100, D=1000, E=10000.E-96 Series Standard Resistance Lookup Table (Partial)ValueCodeValueCodeValueCode100011471721533102021501822134105031541922635107041582023236110051622123737113061652224338115071692324939118081742425540121091782526141124101822626742127111872727443130121912828044133131962928745137142003029446140152053130147143162103230948 ValueCodeValueCodeValueCode316494646568181324504756669882332514876771583340524996873284348535116975085357545237076886365555367178787374565497280688383575627382589392585767484590402595907586681412606047688792422616197790993432626347893194442636497995395453646658097696EIA-96 Calculation Examples:Code 29B: Lookup "29" in table → Value 196.Multiplier "B" → x10.Result: 196 × 10 = 1.96 kΩCode 10X: Lookup "10" in table → Value 124.Multiplier "X" → x0.1.Result: 124 × 0.1 = 12.4 ΩCase 4: The Underlined Code (Special 0603 Case)Sometimes you see a standard 3-digit code with a line under it on an 0603 package. This usually indicates the manufacturer uses the E-24 series values (loose tolerance) rather than E-96, but the calculation is standard.122 = 12 × 100 = 1.2 kΩ680 = 68 × 1 = 68 Ω (Note: 680 does not mean 680 ohms here, it means 68 and zero extra zeros). Ⅲ How to Identify Damaged SMD Resistor Values?When a resistor is burned or the marking is unreadable, use these four forensic engineering methods to deduce the value:1. Parallel Circuit ComparisonPCB designs, especially in power supplies and audio amplifiers, often use symmetrical channels. • Example: In an LCD backlight driver, if the resistor in Channel A is burnt, check the corresponding position in Channel B. Often R17 = R51, or R23 = R48. Measure the intact sibling component to find the value.2. Circuit Context Analysis (Pull-Up/Pull-Down)For Microcontroller (MCU) circuits, resistors connected to GPIO pins are typically "pull-up" or "pull-down" resistors used to stabilize logic levels.• Common Values: 3.3kΩ, 4.7kΩ, 10kΩ.• Deduction: If the resistor connects a data line to VCC or GND, replacing it with a 10kΩ resistor is a safe starting point for testing.3. Reference Similar SchematicsIf the exact schematic is unavailable, search for schematics of devices using the same main IC. Manufacturers often use the "Reference Design" provided by the chipmaker, meaning the peripheral resistor values will be identical across different brands.4. The Potentiometer Test (Advanced)If all else fails, trace the circuit diagram. Temporarily solder a high-value potentiometer (variable resistor) in place of the damaged part. Power on the device and slowly adjust the resistance while monitoring voltage levels until the circuit functions correctly. Remove the potentiometer, measure its set resistance, and replace it with the closest standard fixed resistor.  Ⅳ Top SMD Resistor Manufacturers (2026 Updated)Reliability is paramount in 2026 electronics. The following brands are currently recognized as Tier-1 manufacturers for automotive, industrial, and consumer electronics:YAGEO: Global leader in chip resistors (acquired KEMET).Vishay: Known for high-precision, military-grade foil resistors.Panasonic: Industry standard for high-reliability automotive parts.KOA Speer: Major supplier for automotive and industrial markets.Bourns: Famous for circuit protection and resistors.TE Connectivity: Specialist in harsh environment resistors.Other Notable Brands: ROHM, Ohmite, Welwyn, TT Electronics, UNI-ROYAL (Uniohm). ⅴ Frequently Asked Questions (FAQ)1. What is an SMD resistor used for?SMD (Surface Mount Device) resistors limit current, divide voltage, and stabilize signal lines in compact electronic circuits. They are essential for miniaturizing devices like smartphones, wearables, and IoT sensors where traditional through-hole components would be too bulky. 2. How do I calculate the value of a 3-digit SMD resistor?Use the formula: [1st Digit][2nd Digit] x 10^[3rd Digit]. For example, "103" means 10 x 10^3 (1000) = 10,000 Ohms or 10kΩ. 3. What does "R" mean in a resistor code like 4R7?The letter "R" represents the decimal point. It is used when the resistance value is too small to use a multiplier code. Therefore, 4R7 equals 4.7 Ohms. 4. What is the difference between 103 and 1002 markings?Both equal 10kΩ, but the marking indicates tolerance. "103" (3-digit) typically indicates ±5% tolerance. "1002" (4-digit) indicates higher precision, typically ±1% tolerance. 5. How do I read the cryptic "01A" or "29B" codes?These are EIA-96 codes for 1% precision resistors on small 0603 parts. You cannot read them directly; you must use an EIA-96 lookup table. The number refers to a value code, and the letter is the multiplier. 6. Why do some SMD resistors have no markings?Resistors in package sizes 0402, 0201, and 01005 are physically too small to print legible text. To identify these, you must measure them with a multimeter or refer to the manufacturer's reel tape packaging. 7. What does SMD stand for?SMD stands for Surface Mounted Device. It refers to the component itself. SMT (Surface Mount Technology) refers to the manufacturing process of placing these components onto a PCB. 8. What materials are SMD resistors made of?Most SMD resistors are "Thick Film" or "Thin Film" types. They consist of a ceramic substrate (alumina) coated with a resistive paste (metal oxides and glass). This is fired in a kiln, laser-trimmed to the exact value, and then coated with a protective layer.{ "@context": "https://schema.org", "@type": "Article", "mainEntityOfPage": { "@type": "WebPage", "@id": "https://www.kynix.com/Blog/How-to-Read-the-Value-of-SMD-Resistor-Example-Explained.html" }, "headline": "How to Read SMD Resistor Codes: The 2026 Guide to 3-Digit, 4-Digit & EIA-96 Markings", "image": "https://www.kynix.com/editor_u/image/20211027/2021102711243403.jpg", "author": { "@type": "Organization", "name": "Kynix Electronics" }, "publisher": { "@type": "Organization", "name": "Kynix Electronics", "logo": { "@type": "ImageObject", "url": "https://www.kynix.com/logo.png" } }, "datePublished": "2021-10-27", "dateModified": "2026-01-08", "description": "Learn how to calculate SMD resistor values using 3-digit, 4-digit, and EIA-96 codes. Includes updated 2026 lookup tables and troubleshooting steps for damaged components.", "articleBody": "SMD Resistor, called Chip Resistor, is one type of resistors..."}{ "@context": "https://schema.org", "@type": "FAQPage", "mainEntity": [{ "@type": "Question", "name": "What is an SMD resistor used for?", "acceptedAnswer": { "@type": "Answer", "text": "SMD (Surface Mount Device) resistors limit current, divide voltage, and stabilize signal lines in compact electronic circuits like smartphones and IoT devices." } }, { "@type": "Question", "name": "How do I calculate the value of a 3-digit SMD resistor?", "acceptedAnswer": { "@type": "Answer", "text": "Use the formula: [1st Digit][2nd Digit] x 10^[3rd Digit]. For example, 103 means 10 x 1000 = 10,000 Ohms (10kΩ)." } }, { "@type": "Question", "name": "What does 'R' mean in a resistor code like 4R7?", "acceptedAnswer": { "@type": "Answer", "text": "The letter 'R' acts as a decimal point. 4R7 represents 4.7 Ohms." } }, { "@type": "Question", "name": "How do I read EIA-96 codes like 01A?", "acceptedAnswer": { "@type": "Answer", "text": "EIA-96 codes require a lookup table. The number represents a significant value, and the letter represents a multiplier. For '01A', 01 is 100 and A is x1, resulting in 100 Ohms." } }]}{ "@context": "https://schema.org", "@type": "HowTo", "name": "How to Read a 3-Digit SMD Resistor Code", "description": "Step-by-step guide to calculating resistance from standard 3-digit markings found on most chip resistors.", "step": [{ "@type": "HowToStep", "name": "Identify the Significant Digits", "text": "Read the first two numbers on the resistor. These are your significant digits (e.g., in '103', the significant digits are '10')." }, { "@type": "HowToStep", "name": "Identify the Multiplier", "text": "Read the third number. This indicates the power of 10 to multiply by (or how many zeros to add). In '103', the multiplier is 3 (10^3 or 1000)." }, { "@type": "HowToStep", "name": "Calculate the Result", "text": "Multiply the significant digits by the multiplier. 10 x 1000 = 10,000 Ohms (10kΩ)." }]}

Introduction The operational amplifier has a non-inverting input terminal and an inverting input terminal in the electronic circuit. The polarity of the input terminal and the output terminal are the same is a non-inverting amplifier, and the polarity of the input terminal and the output terminal are opposite called inverting amplifier. The inverting amplifier circuit has the function of amplifying the input signal as inverting output. Inverting Op Amp and The Concept of Virtual Ground in Op Amp Catalog Introduction Ⅰ Inverting Amplifier Basics Overview 1.1 Working Principle 1.2 Inverting Amplifier Gain Calculator 1.3 Inverting Amplifier Features 1.4 Inverting Amplifier Functions Ⅱ Inverting Amplifier Applications Ⅲ Inverting Amplifier Explain with Diagrams: NE5532 Ⅳ Inverting Amplifier Circuit Design Steps Ⅴ FAQ Ⅰ Inverting Amplifier Basics Overview 1.1 Working Principle As shown in Figure 1, the inverting amplifier circuit has the function of amplifying the input signal as inverting output. "Inverting" means that the positive and negative signs are reversed. This amplifier uses negative feedback technology, which used to return a part of the output signal to the input. In Figure, the wiring method of connecting the output Vout to the inverting input terminal (-) via R2 is negative feedback. Figure 1. Inverting Amplifier Circuit Operational amplifiers have such characteristics. When the power supply voltage is not applied to the output terminal, the non-inverting input terminal (+) and the inverting input terminal (-) are considered to have the same voltage, that is to say, it can be regarded as a virtual short circuit. Therefore, when the positive input terminal (+) is 0V, the voltage at output is also 0V.The input impedance of the operational amplifier is extremely high, and there is basically no current in the inverting input terminal (-). Therefore, when the current flows to R2, the I1 and I2 are basically equal. Based on the above conditions, using Ohm's Law for R2, we get Vout=-I1xR2. I1 is negative because I2 flows from point A where the voltage is 0V. From another point of view, when the input voltage of the inverting input terminal (-) rises, the output will be inverted and amplified greatly in the negative direction. Since the output voltage in the negative direction is connected to the inverting input terminal via R2, the voltage rise of the inverting input terminal (-) will be blocked. Both the inverting input terminal and the non-inverting input terminal voltage become 0V, and the output voltage is stable.   1.2 Inverting Amplifier Gain Calculator Calculate the gain through the relationship between the input and output in this amplifier circuit. The gain of an inverting op amp is the ratio of the feedback resistance to the input resistance, that is, the ratio of Vout to Vin, and the formula is Vout/Vin= (-I1xR2) /(I1xR1)=-R2/R1. The resulting gain is negative, indicating that the waveform is inverting.The current flowing through R1: I1=(Vi-V-)/R1...aThe current flowing through R2: I2=(V--Vout)/R2……bV-=V+=0………………cI1=I2……………………dSolve the above algebraic equations to get Vout=(-R2/R1)*Vi.This is the input and output relationship of the inverting amplifier circuit.   1.3 Inverting Amplifier Features It can reduce the input impedance or keep a certain value.It can be used as a current input type.Virtual short-circuit point is generated at a certain potential.Its positive input port is free.If the signal source impedance is low, it is easier to obtain a required S/N.The magnification is -Rf/R.   1.4 Inverting Amplifier Functions The inverting amplifier is the basic gain stage in the CMOS circuit. It adopts a common source structure, and the load can be an active load or a current source.Advantages: The potential of the two input terminals is always approximately zero (the non-inverting terminal is grounded, and the inverting terminal is virtual ground). With only differential mode signals,it has strong anti-interference ability.Disadvantages: The input impedance is very small, equal to the resistance of the series resistance from the signal to the input.   Ⅱ Inverting Amplifier Applications Figure 2. Basic Inverting Amplifier Circuit 1) As a IntegratorThe original resistor R2 of the inverting amplifier is replaced by a capacitor C2. At this time, the relationship between the input signal Vi and the output signal Vo forms an integral relationship.2) As a DifferentiatorReplace the original resistor R1 of the inverting amplifier with an electric capacitor C. At this time, the relationship between the input signal Vi and the output signal Vo is differential.3) As a AdderIf the inverting amplifier is slightly changed, the relationship between the input signal and the output signal Vo at this time, if R1 = R2 = R3 =...= Rn = Rf, it can be simplified to Vo = -(V1+V2+V3+.. .+Vn), is additive.   Ⅲ Inverting Amplifier Explain with Diagrams: NE5532 The equivalent resistance seen between the input terminal and the ground of the inverting amplifier circuit is equal to the equivalent resistance between the input terminal and the virtual ground, so the input resistance of the circuit is Ri=R. It can be seen that although the input resistance of the ideal operational amplifier is infinite, the input resistance of the inverting proportional arithmetic circuit is not large because of the parallel negative feedback introduced by the circuit. Figure 3. NE5532 Audio Amplfier Circuit In order to increase the input resistance, R must be increased. For example, when the scale factor is -50, if Ri=10kΩ, R should be 10kΩ and Rf should be 500kΩ. If Ri=100kΩ, R should be 100kΩ and Rf should be 5MΩ. In fact, when the resistance in the circuit is too large, on the one hand, due to the process, the stability of the resistance is poor and the noise is large, on the other hand, when the resistance is of the same order of magnitude as the input resistance of the integrated op amp, the proportional coefficient -Rf/R of the circuit will change greatly, and its value will not only be determined by the feedback network. Therefore, it is necessary for practical applications to use a resistor with a smaller resistance value to get a larger scale factor and a larger input resistance.Look at the following two simulations: Figure 4. Current and Voltage Measuring From above, it doesn't matter without R0, take a look at this below. Figure 5. Current and Voltage Measuring Their output is different, if the expected result is -4V. The reading value -3.608V obviously does not meet the design requirements. We now know that the resistance value of Rs in Figure 5 is orders of magnitude greater than the input resistance of the integrated operational amplifier. Next, if have R0, look at the picture below. Figure 6. Current and Voltage Measuring It can be seen from Figure 6 that after adding R0, the output of the op amp is normal. Why is this?In a TTL circuit, the transistor has a bias current, which will produce a DC voltage drop on the feedback resistor of the e pole. Although it is small, the amplifier has a high amplification factor, which affects the output accuracy greatly. A resistor in the same value as the negative terminal is connected to the positive terminal to cancel the effect of the bias current.R0 is a compensation resistor, which minimizes the bias current error to ensure the symmetry of the differential amplifier circuit of the input stage. When its value is u=0 (that is, the input terminal is grounded), the inverting input terminal is always the equivalent resistance, that is, the parallel connection of the resistance of each branch, so R0=Rs/Rf, through Rf in the circuit, induce negative feedback. According to practical experience, it is best to add a compensation resistor to improve the stability of the circuit. Of course, it can be omitted under normal circumstances.   Ⅳ Inverting Amplifier Circuit Design Steps Inverting amplifiers are several commonly used amplifier types. How to use operational amplifiers design inverting amplifier circuit? The following sharing is the detailed steps.Step 1: Determine the magnification.As shown in the figure below, the amplification factor of the inverting amplifier is (-R2/R1). Figure 7. Determine the Magnification Step 2: Determine the supply voltage.Ensure that the output voltage after the input voltage Vin is multiplied by the amplification factor (-R2/R1) will not exceed the power supply voltage. If it is not the rail-to-rail operational amplifier used, it is better to have a margin of 1~2V. Figure 8. Determine the Supply Voltage Step 3: Determine the gain bandwidth product (GBW).If you are amplifying an AC signal, you need to consider the gain bandwidth product. The calculation formula is: bandwidth of input signal × design gain, select an operational amplifier whose GBW is greater than the required one. Step 4: Check the bandwidth with the slew rate (SR).If the amplifying is a large AC signal, there may be insufficient bandwidth, and it may not be accurate enough to calculate based on the gain-bandwidth product.SR = 2*pi*f*Vp -> f = SR/(2*pi*Vp), where Vp: peak output voltage.If the calculated value f is less than the input voltage frequency, the operational amplifier is not suitable and needs to be replaced. The actual bandwidth should be the smaller of the gain bandwidth product and the slew rate. Step 5: Determine the input offset voltage.Since the offset voltage is also a DC signal, if it is to amplify the DC signal, it should be noted that the offset voltage will also be amplified by the corresponding multiple. If the accuracy is high, try to choose an operational amplifier with a small offset voltage. Step 6: Determine the resistance value.In step 1, the ratio of R1 and R2 has been determined. R1 is generally 1k~10k. A small value is prone to cause gain errors, and a larger value will increase noise (resistor thermal noise). R2 takes the resistance value corresponding to the multiple of R1.It is better to choose the chip resistor, because the parasitic parameters are small.R3=R1/R2, if R1 and R2 are connected in parallel, which are not required.   Ⅴ FAQ 1. What is the inverting amplifier?An inverting op amp is an operational amplifier circuit with an output voltage that changes in the opposite direction as the input voltage. In other words, it is out of phase by 180o。   2. What is inverting amplifier and its application?The inverting amplifier is an important circuit configuration using op-amps and it uses a negative feedback connection. An inverting amplifier, like the name suggests, inverts the input signal as wells as amplifies it.   3. How does an inverting amplifier circuit work?In an inverting amplifier circuit, the operational amplifier inverting input receives feedback from the output of the amplifier. Assuming the op-amp is ideal and applying the concept of virtual short at the input terminals of op-amp, the voltage at the inverting terminal is equal to non-inverting terminal.   4. What are the applications of inverting amplifier?op-amp inverting amplifier. Op amp summing amplifier: Based around the inverting amplifier circuit with its virtual earth summing point, this circuit is ideal for summing audio inputs. It is widely used in audio mixer and many other applications where voltages need to be summed.   5. Why is it called inverting amplifier?It is called Inverting Amplifier because the op-amp changes the phase angle of the output signal exactly 180 degrees out of phase with respect to input signal. Same as like before, we use two external resistors to create feedback circuit and make a closed loop circuit across the amplifier.   6. What are the characteristics of inverting amplifier?1) No Current Flows into the Input Terminals.2) The Differential Input Voltage is Zero as V1 = V2 = 0 (Virtual Earth)   7. What is the formula of inverting amplifier?One final point to note about the Inverting Amplifier configuration for an operational amplifier, if the two resistors are of equal value, Rin = Rƒ then the gain of the amplifier will be -1 producing a complementary form of the input voltage at its output as Vout = -Vin.   8. What are advantages and disadvantages of inverting amplifier?Advantages and Disadvantages of Inverting AmplifierIt follows the negative feedback. The gain factor of these amplifiers is very high. The output generated will be out of phase with the applied input signal. The potential values at both the inverting and the non-inverting terminals maintained at zero.   9. What are the advantages of inverting amplifier?The op amp circuit for the inverting amplifier offers many advantages including relatively low input impedance, a low output impedance and the level of gain that is required (within the limits of the op amp and the gain required from the overall circuit.   10. What is the use of inverting amplifier?The inverting amplifier is an important circuit configuration using op-amps and it uses a negative feedback connection. An inverting amplifier, like the name suggests, inverts the input signal as wells as amplifies it.   11. What is mean by inverting amplifier?An inverting amplifier takes an input signal and turns it upside down at the op amp output. When the value of the input signal is positive, the output of the inverting amplifier is negative, and vice versa. ... The amount of amplification depends on the ratio between the feedback and input resistor values.   12. How an opamp is used as inverting amplifier?Theory: An inverting amplifier using opamp is a type of amplifier using opamp where the output waveform will be phase opposite to the input waveform. The input waveform will be amplifier by the factor Av (voltage gain of the amplifier) in magnitude and its phase will be inverted.   13. What is an inverting amplifier used for?op-amp inverting amplifier. Op amp summing amplifier: Based around the inverting amplifier circuit with its virtual earth summing point, this circuit is ideal for summing audio inputs. It is widely used in audio mixer and many other applications where voltages need to be summed.   14. How does an inverting amplifier work?An inverting amplifier takes an input signal and turns it upside down at the op amp output. When the value of the input signal is positive, the output of the inverting amplifier is negative, and vice versa.   15. What is the gain of an inverting amplifier?The gain of inverting amplifier is Av= – Rf/Ri.

Introduction Capacitors are now commonly used as decoupling capacitors, DC blocking capacitors, or as matching capacitors due to their characteristics of blocking DC while passing AC. But in practical applications, DC can charge the capacitor and pass through it. Is this contrary to its characteristics? Why can DC charge the capacitor? Here we will discuss this issue in details. Charging and Discharging of Capacitor -RC Circuit Catalog Introduction Ⅰ Capacitor Charging Principle Ⅱ Why Capacitor Charges in DC? Ⅲ Capacitor Transient and Steady-state Processes Ⅳ Capacitor Circuit Analysis and Calculations Ⅴ FAQ Ⅰ Capacitor Charging Principle A capacitor is a component that can store electrical energy. As one of the most commonly used electronic components, the simplest capacitor is composed of plates at both ends and an insulating dielectric (including air) in the middle. After being energized, the plates are charged to form a voltage (potential difference), but due to the insulating material in the middle, the entire capacitor is non-conductive. However, this situation is under the premise that the critical voltage (breakdown voltage) of the capacitor is not exceeded. In fact, any substance is relatively insulating. When the voltage across the substance increases to a certain level, the substance can conduct electricity. We call this voltage breakdown voltage.It is the same for the capacitor. After the capacitor is broken down, it is not an insulator. In an AC circuit, because the direction of the current changes with time as a certain function. The process of charging and discharging a capacitor takes time. At this time, a changing electric field is formed between the plates, and it is also a function of time. So current passes between capacitors in the form of an electric field.Capacitors are similar to batteries in that they also have two electrodes. Inside the capacitor, the two electrodes are connected to two metal plates separated by a dielectric. When the capacitor is connected to the power supply, under the action of the electric field force, the free electrons of the capacitor plate connected to the positive electrode of the power supply will move to the negative electrode. The positive electrode is positively charged due to the loss of negative electrons, and the negative electrode is negatively charged due to its negative electrons. In addition, the charges on the positive and negative plates are equal, with opposite signs.The directional movement of the charge forms a current. Due to the repulsion of the same charges, the current is the largest at first, and then gradually decreases. During the charge movement, the charge stored in the capacitor plate continues to increase, and the charge stops moving when the voltage between the two plates of the capacitor is equal to the power supply voltage. That is, the current I=0, the switch is closed, and the positive and negative plates of the capacitor are neutralized through the connection of the wires. When the switch is closed, the positive charge of the positive pole of the capacitor can be moved to the negative pole and neutralized. When the charge gradually decreases, the current decreases, and the voltage gradually decreases to zero.   Ⅱ Why Capacitor Charges in DC? Why is there a charging current that lasts for a period of time when using DC to charge a capacitor? At this time, the circuit is equivalent to an open circuit, there is no continuous current without a loop, and the capacitor charging has time, not instantaneously, so the instantaneous current is not the answer. Having a potential difference, how does a circuit without a closed loop produce a charging current that lasts for a period of time? Figure 1. Transition Process When Charging the Capacitor The voltage across the capacitor is not allowed to change suddenly. So when the power is turned on, the voltage across the capacitor is equal to zero, and then the voltage rises exponentially until it enters a steady state. The capacitor after entering the steady state is equivalent to an open circuit. In fact, the capacitor can block the constant direct current and disconnect when it fully charged in the circuit. According to the leakage resistance of the capacitor, the charge can be stored in the capacitor for a long period of time.When Usr is instantly added to the resistor-capacitor circuit, because the voltage across the capacitor is not allowed to change suddenly, the capacitor is equivalent to being short-circuited at this time. So at time 0, the current flowing through the capacitor and resistor R is .Then the capacitor began the charging process, and the current became smaller and smaller. After 5 times the RC time, the capacitor charging is basically over and the current is reduced to zero. Since then, it has entered a steady state. The RC(τ) here is called the time constant.We know that resistance is equal to the ratio of voltage to current, that is, R=U/I. We also know that the capacitance C is equal to the ratio of the electric quantity Q to the voltage U, and the electric quantity Q is equal to the product of the current I and the time t .It turns out that the product of resistance and capacitance is time. The unit of resistance is ohms and the unit of capacitance is farads, so the unit of time is seconds.In Figure 1, when the capacitor is charged, the voltage across it is .We find Uc when t=0, 1RC, 2RC, 3RC, 4RC, and 5RC, as follows: It can be seen that when time t=0, the voltage across the capacitor is equal to zero; when t=5RC, the voltage across the capacitor is almost equal to the input voltage.Let's look at the current flowing through the capacitor, its expression is as follows: When t=5RC, where .It can be seen that the current at this time is almost equal to zero. Therefore, the transient process and steady-state process of the capacitor must be clearly distinguished.   Ⅲ Capacitor Transient and Steady-state Processes 1) There are transient and steady-state processes in the capacitor charging circuit.2) At the beginning of capacitor charging, it must be considered that the voltage across the capacitor does not allow sudden changes, which is an important principle.3) The transient process generally ends after 5τ.4) For Figure 1, at the moment of the transient start, the capacitor voltage Uc is equal to zero, and the current Ic is equal to the maximum value. We know from Ohm's law that the equivalent resistance of the capacitor is equal to zero . Usually we say that the capacitance at this time is equal to the short circuit i. In the steady state at the end of the transient, the capacitor voltage Uc is equal to the input voltage Usr, and the capacitor current Ic=0. According to the Ohm's law that the equivalent resistance of the capacitor is equal to infinity . At this time, the capacitance is equivalent to an open circuit.5) If the input signal voltage is a short pulse, the capacitor can transmit the signal to the load; if the input signal is a constant voltage, the capacitor will only respond during a short transition, and then block the input signal; if the input signal is an AC signal, which is exactly in the middle of the above two situations.The higher the frequency of the AC signal, the easier it is to pass through the capacitor. We call this feature a high-pass filter function. Although the AC signal can pass through the capacitor, there will be a certain amount of clipping. This shows that the capacitor has the function of isolating DC in the steady state, and a high-pass characteristic. So we can further analyze, any circuit with capacitor and inductor, we must analyze the circuit according to the transient state and the steady state, in order to get the correct analysis result.   Ⅳ Capacitor Circuit Analysis and Calculations The analysis is available from the figure below: Figure 2. Output Voltage Usc If set Usr=10Vdc, the capacitance is equal to 10 microfarads, and the resistances R1 and R2 are both 1 kiloohm, then how to analyze the value of Usc?Step 1: Determine the time constant of the capacitor. Figure 3. Usr in Short-circuit Connection From the analysis of the above figure, it can be seen that the time constant is 20 milliseconds , and the time for 5 times the time constant is 0.1 seconds.Step 2: Let's calculate the specific value of Usc.When Usr in Figure is just established, the capacitor voltage drop is equal to zero, so there is .After 5τ, the capacitor is full of voltage, and its value is Uc=Usr, so Usc=0, .When charging starts, t=0, When the time has passed 0.1 second, we have , and the Usc at this time is almost equal to zero. Now, let's connect R1 and C in parallel, and see what happens: Figure 4. R1 and C are Connected in Parallel We see that if Usr in the figure is short-circuited, R1 and R2 are connected in parallel, so the time constant is At the beginning of Usr power on, C is equivalent to a short circuit, and Usr is directly loaded on both ends of the resistor R2, so at this time Usc=UseWhen the circuit enters a steady state, Usc is equivalent to the partial pressure of Usr by resistors R2 and R1, namely Based on this, we can derive the following equation: .In the above formula, the first term on the right side of the equal sign is the change in capacitor voltage, which reflects the transition process. The second term on the right side of the equal sign is the final steady-state voltage.Substitute the parameters, and calculate the time constant first: .In other words, when the time is 5τ, that is, 25 microseconds, the output voltage tends to stabilize. The final value is .It is still 5V, but the transition process is only 25 microseconds, which is much shorter than the previous 0.1 second.   Ⅴ FAQ 1. When a capacitor is charging in a DC circuit?At this point, the electric field between the plates cancels the effect of the electric field generated by the battery, and there is no further movement of charge. Thus, if a capacitor is placed in a DC circuit then, as soon as its plates have charged up, the capacitor effectively behaves like a break in the circuit.   2. What happens to the current in a DC circuit once a capacitor is charged?For a capacitor charge Q = capacitance C multiplied by voltage V. This quite simply means that a rate of change of voltage gives rise to a current. If the voltage is rising linearly with time, the capacitor will take a constant current and once the voltage stops changing the current is zero.   3. Does current flow in a DC circuit while a capacitor is charging?Yes. For DC circuits, when a capacitor is charged or discharged, current is flowing into and out of it. For AC circuits, a capacitor can act almost like a "resistor" but instead it is called reactance. But alas, current does flow through the capacitor.   4. Do capacitors charge with AC or DC?When DC current is applied to a circuit with only resistance and capacitance, the capacitor will charge to the level of the applied voltage. Since DC only flows in one direction, once the capacitor is fully charged there is no more current flow.   5. Can we use capacitor in DC?Capacitors can be used in many different applications and circuits such as blocking DC current while passing audio signals, pulses, or alternating current, or other time varying wave forms. ... At DC a capacitor has infinite impedance (open -circuit), at very high frequencies a capacitor has zero impedance (short-circuit).   6. Can a capacitor be charged by DC?When capacitor is connected to dc voltage source, capacitor starts the process of acquiring a charge. This will built up voltage across capacitor. Once capacitor has acquire enough charge, current starts flowing and soon capacitor voltage reaches at value approximately equal to dc source voltage.   7. Why does AC pass through capacitor but not DC?Capacitors have two parallel metallic plates placed close to each other and there is a gap between plates. A capacitor blocks DC but it allows AC. ... Therefore the electrons flowing in one direction (i.e. DC) cannot pass through the capacitor. But the electrons from AC source seem to flow through C.   8. What happens when capacitor is connected to DC?When capacitors are connected across a direct current DC supply voltage, their plates charge-up until the voltage value across the capacitor is equal to that of the externally applied voltage. ... Then the Capacitance in AC circuits varies with frequency as the capacitor is being constantly charged and discharged.   9. Why capacitor is used in DC circuit?Capacitors are useful to reduce the voltage pulsation. When the high voltage is applied to the parallel circuit, the capacitor is charged, and on the other hand, it is discharged with the low voltage. While electricity flowing out is alternating current, most of electronic circuits work with direct current.   10. Why do capacitors block DC current?We know that there is no frequency i.e. 0Hz frequency in DC supply. If we put frequency “f = 0″ in the inductive reactance (which is AC resistance in capacitive circuit) formula. If we put XC as infinity, the value of current would be zero. That is the exact reason why a capacitor block DC.   11. How is a capacitor charged in a DC circuit?When used in a direct current or DC circuit, a capacitor charges up to its supply voltage but blocks the flow of current through it because the dielectric of a capacitor is non-conductive and basically an insulator. ... At this point the capacitor is said to be “fully charged” with electrons.   12. Which capacitor is used in DC circuit?Decoupling capacitor is used, where we have to decouple the two electronics circuits. In other words, the noise generated by one circuit is grounded by decoupling capacitor and it does not affect the performance of other circuit.   13. Can you charge a capacitor with DC current?A DC voltage source is used to charge a Capacitor. When the DC voltage source is outputting more than the DC voltage source can charge, the Capacitor will charge up. Capacitors will charge up to 9 volts if they are connected to a 9-volt battery.   14. What happens if DC is applied to capacitor?When capacitors are connected across a direct current DC supply voltage, their plates charge-up until the voltage value across the capacitor is equal to that of the externally applied voltage. ... Then the Capacitance in AC circuits varies with frequency as the capacitor is being constantly charged and discharged.   15. Can we charge capacitor with DC current?When capacitor is connected to dc voltage source, capacitor starts the process of acquiring a charge. This will built up voltage across capacitor. Once capacitor has acquire enough charge, current starts flowing and soon capacitor voltage reaches at value approximately equal to dc source voltage.

  Catalog Ⅰ Introduction Ⅱ Resistor network  in Series vs in Parallels 2.1 Resistor in Series  Ⅲ Resistor Circuit in Series vs in Parallels 3.1 Resistor Circuit in Series 3.2 Resistor Circuit in Parallels Ⅳ Equation in Series vs Parallels 4.1 Series Resistor Equation 4.2 Parallel Resistor Equation Ⅴ Examples 5.1 Resistors in Series Example 5.2 Resistor in Parallels Ⅵ Applications Ⅶ Summary 7.1 Resistors in Series Summary 7.2 Resistors in Parallel Summary Ⅷ FAQ Ⅰ Introduction   Individual resistors can be commonly connected to three types of circuits such as series, parallel, or a combination of series and parallel connections to form more complex resistor networks, the equivalent resistance of which is the mathematical combination of the individual resistors connected together.   A resistor is not only a fundmental electronic component that can be applied to convert a voltage to a current or a current to a voltage but it can also be used to place a different weighting on the converted current and/or voltage by correctly adjusting its value, allowing it to be used in voltage reference circuits and applications.    A single equivalent resistor can take place of resistors in series or complicated resistor networks. REQ, or impedance, ZEQ, and regardless of the resistor network's combination or complexity, all resistors follow the same basic rules defined by Ohm's Law and Kirchhoff's Circuit Laws.   Resistors in Series | Electricity and Circuits | Don't Memorise   Ⅱ Resistor network  in Series vs in Parallels     2.1 Resistor in Series   When resistors are daisy-chained together in a single line, they are connected in "Series." Because there is no other way for the current flowing through the first resistor to go, it has to pass through the second, third, and so on. The current that flows through one resistor should flow through the others as well because it can only take one path, so resistors in series have a Common Current flowing through them.   The current flowing through a series of resistors will then be the same at all points in a series resistor network. As an example:       Figure1：Current flowing through a series     In the following example, resistors R1, R2, and R3 are connected in series between points A and B, with a common current, I, flowing through them.         2.2 Resistor in Parallels In contrast to the previous series resistor circuit, the circuit current in a parallel resistor network can take more than one path because there are multiple paths for the current. Parallel circuits are then classified as current dividers.   Because the supply current can flow through multiple paths, the current may not be the same through all of the parallel network's branches. The voltage drop across all resistors in a parallel resistive network, on the other hand, so it is. Then, parallel-connected resistors have a common voltage across them, as do all parallel-connected elements.       Figure2: Circuit current in a parallel      Ⅲ Resistor Circuit in Series vs in Parallels   3.1 Resistor Circuit in Series         Figure3: Resistor Circuit in series     Because the resistors are linked in series, the same current flows through each resistor in the chain, and the total resistance, RT, of the circuit must equal the sum of all the individual resistors added together. That is            Figure4: resistance     and by taking the individual values of the resistors in our simple example above, the total equivalent resistance, REQ is therefore given as:   REQ = R1 + R2 + R3 = 1kΩ + 2kΩ + 6kΩ = 9kΩ     3.2 Resistor Circuit in Parallels       Figure5: resistor circuit in parallel     The total resistance, RT, of the circuit in the previous series resistor network was equal to the sum of all the individual resistors added together. The equivalent circuit resistance RT is calculated differently for parallel resistors. Instead of the resistances themselves, the reciprocal (1/R) value of each is added together, with the inverse of the algebraic sum giving the equivalent resistance as shown. Instead of the resistances themselves, the reciprocal (1/R) value of each is added together, with the inverse of the algebraic sum giving the equivalent resistance as shown.     Ⅳ Equation in Series vs Parallels 4.1 Series Resistor Equation Because it is the algebraic sum of the individual resistances, the total or equivalent resistance, RT, has the same effect on the circuit as the original combination of resistors. If two equal and of the same value resistances or impedances are connected in series, the total or equivalent resistance, RT, is equal to twice the value of one resistor. That is equal to 2R for two equal resistors in series, 3R for three equal resistors in series, and so on.         Figure6：Series Resistor Equation     If two series resistors or impedances are unequal and of different values, the total or equivalent resistance, RT, is equal to the mathematical sum of the two resistances. R1 + R2 is the answer. The equivalent resistance of three or more unequal (or equal) resistors connected in series is: R1 + R2 + R3 +..., etc.       Figure7：Equivalent resistance     One important thing to remember about resistors in series networks is to double-check your math. The total resistance (RT) of any two or more resistors connected in series is always greater than the value of the chain's largest resistor. In our previous example, RT = 9k, whereas the largest resistor value is only 6k.     4.2 Parallel Resistor Equation         The algebraic sum of the inverses of the individual resistances is the inverse of the equivalent resistance of two or more resistors connected in parallel. If the two parallel resistances or impedances are equal and of the same value, the total or equivalent resistance, RT, is equal to half the value of one resistor. That is R/2 for two equal resistors in parallel, R/3 for three equal resistors in parallel, and so on.       Figure8: Resistances or impedances     Because the equivalent resistance is always less than the smallest resistor in the parallel network, as more parallel resistors are added, the total resistance, RT, will always decrease.     Ⅴ Examples   5.1 Resistors in Series Example Calculate the voltage drops across X and Ya) Without RL connected   b) With RL connected         Figure9: series example     As shown above, the output voltage Vout without the load resistor connected gives us the required output voltage of 6V, but when the load is connected, the output voltage drops to only 4V. (Resistors in Parallel).   Then we can see that a loaded voltage divider network's output voltage changes as a result of the loading effect because the output voltage Vout is determined by the R1 to R2 ratio. However, as the load resistance, RL, approaches infinity (), the loading effect diminishes and the voltage ratio of Vout/Vs is unaffected by the addition of the load on the output. Then, as the load impedance increases, the loading effect on the output decreases.   Attenuation is the effect of lowering a signal or voltage level, so when using a voltage divider network, it is essential to have cautiousness. This loading effect could be compensated for by using a potentiometer instead of fixed value resistors and adjusting the potentiometer accordingly. This method also compensates the potential divider for variations in resistor tolerances.     5.2 Resistor in Parallels   Find the total resistance, RT of the following resistors connected in a parallel network.       Figure10: Total resistance     The total resistance RT across the two terminals A and B is calculated as:       Figure11: Total resistance RT     This reciprocal calculation method can be used to calculate any number of individual resistances connected in a single parallel network. If, on the other hand, there are only two individual resistors connected in parallel, we can use a much simpler and faster formula to find the total or equivalent resistance value, RT, and thus help reduce the reciprocal maths a little.         Figure12: Single parallel network     Ⅵ Applications   Series We've seen how Resistors in Series can be applied to generate different voltages across themselves, and how this genre of resistor network can be used to create a voltage divider network. We can convert an analog quantity being sensed into a suitable electrical signal that can be measured by replacing one of the resistors in the voltage divider circuit above with a Sensor such as a thermistor, light-dependent resistor (LDR), or even a switch.     Parallel The five resistive networks shown above may appear to be different, but they are all arranged as Resistors in Parallel, and thus the same conditions and equations apply.   Ⅶ Summary   7.1 Resistors in Series Summary When two or more resistors are connected end-to-end in a single branch, Reputedly, they are connected in series. Resistors in series carry the same current, but the voltage drop across them is not the same as their resistance values result in different voltage drops across each resistor, as determined by Ohm's Law (V = I*R). Then there are series circuits, which are voltage dividers. Individual resistors in a series resistor network add together to give the series combination's equivalent resistance, (RT). A series circuit's resistors can be swapped without affecting the total resistance, current, or power to each resistor or the circuit.     7.2 Resistors in Parallel Summary   When two or more resistors are connected in such a way that their terminals are connected to the terminals of the other resistor or resistors, they are connected in parallel. The voltage across each resistor in a parallel combination is the same, but the currents flowing through them are not because of their resistance value and Ohms Law. Parallel circuits are then used as current dividers. Reciprocal addition is used to find the equivalent or total resistance, RT, of a parallel combination, and the total resistance value is always less than the smallest individual resistor in the combination. Within the same combination, parallel resistor networks can be swapped without changing the total resistance or total circuit current. Resistors connected in a parallel circuit will continue to operate even if one of them is open-circuited.   Ⅷ FAQ   1. How do you calculate resistors in series? In a series circuit you will need to calculate the total resistance of the circuit in order to figure out the amperage. This is done by adding up the individual values of each component in series. ... To calculate the total resistance we use the formula: RT = R1 + R2 + R3. 2 + 2 + 3 = 7 Ohms. R total is 7 Ohms.     2. Do you add up resistance in series? How do you know if a series resistor is parallel? The trick is to look at the nodes in the circuit. A node is a junction in the circuit. Two resistor are in parallel if the nodes at both ends of the resistors are the same. If only one node is the same, they are in series.   3. Which resistor gets the most current? which resistor has the most current passing through it? the 5-Ω resistor has the most current passing through it, since I = V/R.     4. What is resistor connected in parallel? Resistors are in parallel if their terminals are connected to the same two nodes. The equivalent overall resistance is smaller than the smallest parallel resistor. Written by Willy McAllister.     5. What happens to resistors in parallel? When resistors are connected in parallel, more current flows from the source than would flow for any of them individually, so the total resistance is lower. Each resistor in parallel has the same full voltage of the source applied to it, but divide the total current amongst them.     6. Why do resistors decrease resistance in parallel? Resistors in parallel   In a parallel circuit, the net resistance decreases as more components are added, because there are more paths for the current to pass through. The two resistors have the same potential difference across them. ... The total current in the circuit is the sum of the currents through each branch.