Diode

In this episode, of the I Can't Sleep Podcast, fall asleep learning about diodes. I know that probably sounds too technical of a topic to fall asleep to, but hear me out on this one--diodes are way too technical! And that's why this topic will work tonight.

Happy sleeping!

Transcript

Welcome to the I Can't Sleep Podcast, Where I read random articles from across the web to bore you to sleep with my soothing voice. I'm your host, Benjamin Boster. Today's episode is from a Wikipedia article titled, Diode. A diode is a two-terminal electronic component that conducts current, Primarily in one direction. It has low resistance in one direction and high resistance in the other. A semiconductor diode, The most commonly used type today, Is a crystalline piece of semiconductor material, With a p-n junction connected to two electrical terminals. It has an exponential current-voltage characteristic. Semiconductor diodes were the first semiconductor electronic devices. The discovery of asymmetric electrical conduction across the contact between a crystalline mineral and a metal was made by German physicist Ferdinand Braun in 1874. Today most diodes are made of silicon, But other semiconducting materials such as gallium, Arsenide, And germanium are also used. The obsolete thermionic diode is a vacuum tube with two electrodes, A heated cathode and a plate, In which electrons can flow in only one direction, From cathode to plate. Among many uses, Diodes are found in rectifiers to convert alternating current, AC power, To direct current, DC, To modulation in radio receivers, And can even be used for logic or as temperature sensors. A common variant of a diode is a light-emitting diode, Which is used as electric lighting and status indicators on electronic devices. Main Functions. The most common function of a diode is to allow an electric current to pass in one direction, Called the diode's forward direction, While blocking it in the opposite direction, The reverse direction. As such, The diode can be viewed as an electronic version of a check valve. This unidirectional behavior is called rectification, And is used to convert alternating current, AC, To direct current, DC. As rectifiers, Diodes can be used for such tasks as extracting modulation from radio signals in radio receivers. However, Diodes can have more complicated behavior than this simple on-off action, Because of their non-linear current voltage characteristics. For instance, A diode's forward direction voltage drop varies only a little with the current, And is more so a function of temperature. This effect can be used as a temperature sensor or as a voltage reference. And its high resistance to current flowing in the reverse direction suddenly drops to a low resistance when the reverse voltage across the diode reaches a value called the breakdown voltage. Semiconductor diodes in the forward direction also need to surpass a threshold voltage before being able to conduct electricity. A semiconductor diode's current voltage characteristic can be tailored by selecting the semiconductor materials and the doping impurities introduced into the materials during manufacture. These techniques are used to create special purpose diodes that perform many different functions. For example, Diodes are used to regulate voltage, To protect circuits from high voltage surges, To electronically tune radio and TV receivers, To generate radio frequency oscillations, And to produce light. Tunnel, Gun, And N-pad diodes exhibit negative resistance, Which is useful in microwave and switching circuits. History. Thermionic diodes and solid-state diodes were developed separately at approximately the same time in the early 1900s as radio receiver detectors. Until the 1950s, Vacuum diodes were used more frequently in radios because the early point-contact semiconductor diodes were less stable. In addition, Most receiving sets had vacuum tubes for amplification that could easily have the thermionic diodes included in the tube. Even vacuum tube rectifiers and gas-filled rectifiers were capable of handling some high-voltage, High-current rectification tasks better than the semiconductor diodes that were available at the time. In 1873, Frederick Guss-Ree observed that a grounded white-hot metal ball brought in close proximity to an electroscope would discharge a positively charged electroscope, But not a negatively charged electroscope. In 1880, Thomas Edison observed unidirectional current between heated and unheated elements in a bulb, Later called Edison effect, And was granted a patent on application of the phenomenon for use in a DC voltmeter. About 20 years later, John Ambrose Fleming, Scientific advisor to the Marconi Company and former Edison employee, Realized that the Edison effect could be used as a radio detector. Fleming patented the first true thermionic diode, The Fleming valve, In Britain on 16 November 1904. Throughout the vacuum tube era, Valve diodes were used in almost all electronics such as radios, Television, Sound systems, And instrumentation. They slowly lost market share beginning in the late 1940s due to selenium rectifier technology, And then to semiconductor diodes during the 1960s. Today they are still used in a few high-power applications where their ability to withstand transient voltages and their robustness gives them an advantage over semiconductor devices, And in musical instruments and audiophile applications. In 1874, German scientist Carl Ferdinand Braun discovered the unilateral conduction across a contact between a metal and a mineral. Indian scientist Jagdish Chandra Bose was the first to use a crystal for detecting radio waves in 1894. The crystal detector was developed into a practical device for wireless telegraphy by Greenleaf Whittier Pickard, Who invented a silicon crystal detector in 1903 and received a patent for it on 20 November 1906. Other experimenters tried a variety of other minerals as detectors. Semiconductor principles were unknown to the developers of these early rectifiers. During the 1930s, Understanding of physics advanced, And in the mid-1930s, Researchers at Bell Telephone Laboratories recognized the potential of the crystal detector for application in microwave technology. Researchers at Bell Labs, Western Electric, MIT, Purdue, And in the UK intensively developed point-contact diodes, Crystal rectifiers, Or crystal diodes, During World War II for application in radar. After World War II, AT&T used these in their microwave towers that criss-crossed the United States, And many radar sets used them even in the 21st century. In 1946, Sylvania began offering the 1N34 crystal diode. During the early 1950s, Junction diodes were developed. In 2022, The first superconducting diode effect without an external magnetic field was realized. Etymology At the time of their invention, Asymmetrical conduction devices were known as rectifiers. In 1919, The year tetrodes were invented, William Henry Eccles coined the term diode from the Greek roots di- meaning two, And ode- meaning path. The word diode, However, As well as triode, Tetrode, Pentode, Hexode, Were already in use as terms of multiplex telegraphy. Although all diodes rectify, The term rectifier is usually applied to diodes intended for power supply application in order to differentiate them from diodes intended for small signal circuits. Vacuum tube diodes A thermionic diode is a thermionic valve device consisting of a sealed, Evacuated glass or metal envelope containing two electrodes, A cathode and a plate. The cathode is either indirectly heated or directly heated. If indirect heating is employed, A heater is included in the envelope. In operation, The cathode is heated to red heat, Around 800 to 1000 degrees Celsius. A directly heated cathode is made of tungsten wire and is heated by a current passing through it from an external voltage source. An indirectly heated cathode is heated by infrared radiation from a nearby heater that is formed of nichrome wire and supplied with a current provided by an external voltage source. The operating temperature of the cathode causes it to release electrons into the vacuum, A process called thermionic emission. The cathode is coated with oxides of alkaline earth metals, And as barium and strontium oxides, These have a low work function, Meaning that they more readily emit electrons than would the uncoated cathode. The plate not being heated does not emit electrons, But is able to absorb them. The alternating voltage to be rectified is applied between the cathode and the plate. When the plate voltage is positive with respect to the cathode, The plate electrostatically attracts the electrons from the cathode. So a current of electrons flows through the tube from cathode to plate. When the plate voltage is negative with respect to the cathode, No electrons are emitted by the plate. So no current can pass from the plate to the cathode. Semiconductor diodes Point contact diodes Point contact diodes were developed starting in the 1930s out of the early crystal detector technology and are now generally used in the 3 to 30 GHz range. Point contact diodes use a small diameter metal wire in contact with a semiconductor crystal and are of either non-welded contact type or welded contact type. Non-welded contact construction utilizes the Schottky barrier principle. The metal side is the pointed end of a small diameter wire that is in contact with the semiconductor crystal. In the welded contact type, A small p-region is formed in the otherwise n-type crystal around the metal point during manufacture by momentarily passing a relatively large current through the device. Point contact diodes generally exhibit lower capacitance, Higher forward resistance, And greater reverse leakage than junction diodes. Junction diodes PN junction diode A PN junction diode is made of a crystal of semiconductor, Usually silicon, But germanium and gallium arsenide are also used. Impurities are added to it to create a region on one side that contains negative charge carriers, Electrons, Called an n-type semiconductor, And a region on the other side that contains positive charge carriers, Holes, Called a p-type semiconductor. When the n-type and p-type materials are attached together, A momentary flow of electrons occurs from the n to the p side, Resulting in a third region between the two where no charge carriers are present. This region is called the depletion region because there are no charge carriers, Neither electrons nor holes, In it. The diodes terminal are attached to the n-type and p-type regions. The boundary between these two regions, Called a PN junction, Is where the action of the diode takes place. When a sufficiently higher electrical potential is applied to the p side, The anode, Than to the n side, The cathode, It allows electrons to flow through the depletion region from the n-type side to the p-type side. The junction does not allow the flow of electrons in the opposite direction when the potential is applied in reverse, Creating, In a sense, An electrical check valve. Schottky diode. Another type of junction diode, The Schottky diode, Is formed from a metal semiconductor junction rather than a PN junction, Which reduces capacitance and increases switching speed. Current voltage characteristic. A semiconductor diode's behavior in a circuit is given by its current voltage characteristic. The shape of the curve is determined by the transport of charge carriers through the so-called depletion layer, Or depletion region, That exists at the PN junction between different semiconductors. When a PN junction is first created, Conduction band, Mobile electrons from the N-doped region diffuse into the P-doped region, Where there is a large population of holes, Vacant places for electrons, With which the electrons recombine. When a mobile electron recombines with a hole, Both hole and electron vanish, Leaving behind an immobile positively charged donor, Doped on the N-side, And negatively charged acceptor, Doped on the P-side. The region around the PN junction becomes depleted of charge carriers and thus behaves as an insulator. However, The width of the depletion region, Called the depletion width, Cannot grow without limit. For each electron-hole pair recombination made, A positively charged dopant ion is left behind in the N-doped region, And a negatively charged dopant ion is created in the P-doped region. As recombination proceeds and more ions are created, An increasing electric field develops through the depletion zone that acts to slow and then finally stop recombination. At this point, There is a built-in potential across the depletion zone. Reverse Bias If an external voltage is placed across the diode with the same polarity as the built-in potential, The depletion zone continues to act as an insulator, Preventing any significant electric current flow, Unless electron-hole pairs are actively being created in the junction by, For instance, Light. This is called the reverse bias phenomenon. Forward Bias However, If the polarity of the external voltage opposes the built-in potential, Recombination can once again proceed, Resulting in a substantial electric current through the PN junction, I. E. Substantial numbers of electrons and holes recombine at the junction. Unless if an external voltage greater than and opposite to the built-in voltage is applied, A current will flow and the diode is said to be turned on as it has been given an external forward bias. For simplicity, A diode is commonly said to have a forward threshold voltage, Above which it conducts and below which conduction stops. However, This is only an approximation as the forward characteristic is gradual in its current voltage curve. Forward Threshold Operating Regions A diode's current voltage characteristic can be approximated by four operating regions. From lower to higher bias voltages, These are Breakdown At very large reverse bias, Beyond the peak inversion voltage, PIV, A process called reverse breakdown occurs that causes a large increase in current, I. E. A large number of electrons and holes are created at and move away from the PN junction, That usually damages the device permanently. The avalanche diode is deliberately designed to use in that manner. In the Zener diode, The concept of PIV is not applicable. A Zener diode contains a heavily doped PN junction, Allowing electrons to tunnel from the valence band of the P-type material to the conduction band of the N-type material, Such that the reverse voltage is clamped to a known value, Called the Zener voltage, And avalanche does not occur. Both devices, However, Do have a limit to the maximum current and power they can withstand in the clamped reverse voltage region. Also, Following the end of forwarding conduction in any diode, There is reverse current for a short time. The device does not attain its full blocking capability until the reverse current ceases. Reverse biased. For a bias between breakdown and 0V, The reverse current is very small. For a normal PN rectifier diode, The reverse current through the device in the microampere range is very low. However, This is temperature dependent, And at sufficiently high temperatures, A substantial amount of reverse current can be observed. There is also a tiny surface leakage current caused by electrons simply going around the diode as though it were an imperfect insulator. Forward biased. The current-voltage curve is exponential in accordance with the Shockley diode equation. When the forward voltage is smaller than the barrier potential of the PN junction, At which point the diode starts to conduct significantly, Which gives rise to the name's forward threshold voltage or cut-in voltage. When plotting using a large linear current scale, This voltage level appears at the smooth knee of a sharp exponential rise, So it may be called the knee voltage. Note this voltage may loosely be referred to simply as the diode's forward voltage drop, Since a consequence of the steepness of the exponential is that a diode's voltage drop will not significantly exceed the threshold voltage under normal forward bias operating conditions. Data sheets typically quote a typical or maximum forward voltage for a specified current and temperature, So the user has a guarantee about where in the knee a certain amount of current will kick in. Leveling off. At larger forward currents, The current-voltage curve starts to be dominated by the ohmic resistance of the bulk semiconductor. The curve is no longer exponential, It is asymptotic to a straight line whose slope is the bulk resistance. This region is particularly important for power diodes and can be modeled by a Shockley ideal diode in series with a fixed resistor. Shockley diode equation. The Shockley ideal diode equation, Or the diode law, Named after the bipolar junction transistor co-inventor William Bradford Shockley, Models the exponential current-voltage-I-V relationship of diodes in moderate forward or reverse bias. Small signal behavior. A forward voltage less than the saturation voltage. The voltage versus current characteristic curve of most diodes is not a straight line. In detector and mix applications, The current can be estimated by a Taylor's series. The odd terms can be omitted because they produce frequency components that are outside the pass band of the mixer or detector. Even terms beyond the second derivative usually need not be included because they are small compared to the second order term. The desired current component is approximately proportional to the square of the input voltage, So the response is called square law in this region. Reverse recovery effect. Following the end of forwarding conduction in a PN-type diode, A reverse current can flow for a short time. The device does not attain its blocking capability until the mobile charge in the junction is depleted. The effect can be significant when switching large currents very quickly. A certain amount of reverse recovery time may be required to remove the reverse recovery charge from the diode. During this recovery time, The diode can actually conduct in the reverse direction. This might give rise to a large current in the reverse direction for a short time, While the diode is reverse biased. The magnitude of such a reverse current is determined by the operating circuit, I. E. The series resistance, And the diode is said to be in the storage phase. In certain real-world cases, It is important to consider the losses that are incurred by this non-ideal diode effect. However, When the slew rate of the current is not so severe, E. G. Line frequency, The effect can be safely ignored. For most applications, The effect is also negligible for Schottky diodes. The reverse current ceases abruptly when the stored charge is depleted. This abrupt stop is exploited in step recovery diodes for the generation of extremely short pulses. Types of Semiconductor Diode Normal PN diodes are usually made of doped silicon or germanium. Before the development of silicon power rectifier diodes, Cuprous oxide and later selenium was used. Their low efficiency required a much higher forward voltage to be applied, And required a large heat sink much larger than the later silicon diode of the same current ratings would require. The vast majority of all diodes are the PN diodes found in CMOS integrated circuits, Which include two diodes per pin and many other internal diodes. Avalanche Diodes These are diodes that conduct in the reverse direction when the reverse bias voltage exceeds the breakdown voltage. These are electrically very similar to Zener diodes but break down by a different mechanism, The avalanche effect. This occurs when the reverse electric field applied across the PN junction causes a wave of ionization, Reminiscent of an avalanche, Leading to a large current. Avalanche diodes are designed to break down at a well-defined reverse voltage without being destroyed. The difference between the avalanche diode and the Zener is that the channel length of the former exceeds the mean free path of the electrons, Resulting in many collisions between them on the way through the channel. The only practical difference between the two types is they have temperature coefficients of opposite polarities. Constant Current Diodes These are actually JFETs with the gate shorted to the source and function like a two-terminal current limiting analog to the voltage limiting Zener diode. They allow a current through them to rise to a certain value and then level off at a specific value. Also called CLDs, Constraint Current Diodes, Diode Connected Transistors, Or Current Regulating Diodes. These are point contact diodes. The 1N21 series and others are used in mixer and detector applications in radar and microwave receivers. The 1N34A is another example of a crystal diode. Gun Diodes These are similar to tunnel diodes in that they are made of materials such as GAAS or INP that exhibit a region of negative differential resistance. With appropriate biasing, Dipole domains form and travel across the diode, Allowing high frequency microwave oscillators to be built. Light Emitting Diodes, LEDs In a diode formed from a direct band gap semiconductor such as gallium arsenide, Charge carriers that cross the junction emit photons when they recombine with the majority carrier on the other side. Depending on the material, Wavelengths from the infrared to the near ultraviolet may be produced. The first LEDs were red and yellow, And higher frequency diodes have been developed over time. All LEDs produce incoherent narrow spectrum light. White LEDs are actually a blue LED with a yellow scintillator coating, Or combinations of three LEDs of a different color. LEDs can also be used as low efficiency photodiodes in signal applications. An LED may be paired with a photodiode or phototransistor in the same package to form an optoisolator. Laser Diodes When an LED-like structure is contained in a resonant cavity formed by polishing the parallel end faces, A laser can be formed. Laser diodes are commonly used in optical storage devices and for high speed optical communication. Thermal Diodes This term is used both for conventional PN diodes used to monitor temperature because of their varying forward voltage with temperature, And for Peltier heat pumps for thermoelectric heating and cooling. Peltier heat pumps may be made by semiconductors. Though they do not have any rectifying junctions, They use the differing behavior of charge carriers in N and P type semiconductors to move heat. Photodiodes All semiconductors are subject to optical charge carrier generation. This is typically an undesired effect, So most semiconductors are packaged in light blocking material. Photodiodes are intended to sense light, So they are packaged in materials that allow light to pass, And are usually PIN, The kind of diode most sensitive to light. A photodiode can be used in solar cells, In photometry, Or in optical communications. Multiple photodiodes may be packaged in a single device, Either as a linear array or as a two-dimensional array. These arrays should not be confused with charge-coupled devices. PIN Diodes A PIN diode has a central, Undoped, Or intrinsic layer, Forming a P-type intrinsic N-type structure. They are used as radiofrequency switches and attenuators. They are also used as large-volume ionizing radiation detectors and as photodetectors. PIN diodes are also used in power electronics, As their central layer can withstand high voltages. Furthermore, The PIN structure can be found in many power semiconductor devices, Such as IGBTs, Power MOSFETs, And thyristors. Schottky Diodes Schottky diodes are constructed from metal to semiconductor contact. They have a lower forward voltage drop than PN-junction diodes. Their forward voltage drop at forward currents, Which makes them useful in voltage clamping applications and prevention of transistor saturation. They can also be used as low-loss rectifiers, Although their reverse leakage current is in general higher than that of other diodes. Schottky diodes are majority-carrier devices, And so do not suffer from minority-carrier storage problems that slow down many other diodes, So they have a faster reverse recovery than PN-junction diodes. They also tend to have much lower junction capacitance than PN diodes, Which provides for high switching speeds and their use in high-speed circulatory and RF devices, Such as switched-mode power supply mixers and detectors. Superbarrier Diodes Superbarrier diodes are rectifier diodes that incorporate the low forward voltage drop of the Schottky diode with the surge handling capability and low reverse leakage current of a normal PN-junction diode. Gold-Doped Diodes As a dopant, Gold or platinum acts as recombination centers, Which helps the fast recombination of minority carriers. This allows the diode to operate at signal frequencies at the expense of a higher forward voltage drop. Gold-Doped diodes are faster than other PN diodes, But not as fast as Schottky diodes. They also have less reverse current leakage than Schottky diodes, But not as good as other PN diodes. A typical example is the 1N914. Step-Off or Step-Recovery Diodes The term step recovery relates to the form of the reverse recovery characteristic of these devices. After a forward current has been passing in an SRD and the current is interrupted or reversed, The reverse conduction will cease very abruptly as in a step waveform. SRDs can therefore provide very fast voltage transitions by the very sudden disappearance of the charge carriers. Stebistors or Forward Reference Diodes The term stebistor refers to a special type of diodes featuring extremely stable forward voltage characteristics. These devices are specially designed for low voltage stabilization applications, Requiring a guaranteed voltage over a wide current range and highly stable over temperature. Transient Voltage Suppression Diode, TVS These are avalanche diodes designed specifically to protect other semiconductor devices from high voltage transients. Their PN junctions have a much larger cross-sectional area than those of a normal diode, Allowing them to conduct large currents to ground without sustaining damage. Tunnel Diodes or Esaki Diodes These have a region of operation showing negative resistance caused by quantum tunneling, Allowing amplification of signals in very simple bi-staple circuits. Because of the high carrier concentration, Tunnel diodes are very fast, May be used at low MK temperatures, High magnetic fields, And in high radiation environments. Because of these properties, They are often used in spacecraft. Vericap or Veractor Diodes These are used as voltage-controlled capacitors. These are important in PLL phase-locked loop and FLL frequency-locked loop circuits, Allowing tuning circuits such as those in television receivers to lock quickly on to the frequency. They also enable tunable oscillators in the early discrete tuning of radios, Where a cheap and stable but fixed frequency crystal oscillator provided the reference frequency for a voltage-controlled oscillator. Zener Diodes These can be made to conduct in reverse bias backward, And are correctly termed reverse breakdown diodes. This effect, Called Zener breakdown, Occurs at a precisely defined voltage, Allowing the diode to be used as a precision voltage reference. The term Zener diodes is colloquially applied to several types of breakdown diodes, But strictly speaking, Zener diodes have a breakdown voltage of below 5 volts. Whilst avalanche diodes are used for breakdown voltages above that value. In practical voltage reference circuits, Zener and switching diodes are connected in series and opposite directions to balance the temperature coefficient response of the diodes to near zero. Some devices labeled as high-voltage Zener diodes are actually avalanche diodes. Two equivalent Zeners in series and in reverse order, In the same package, Constitute a transient absorber, Or transorb, A registered trademark. Graphic Symbols The symbol used to represent a particular type of diode in a circuit diagram conveys the general electrical function to the reader. There are alternative symbols for some types of diodes, Though the differences are minor. The triangle in the symbols points to the forward direction, I. E. In the direction of conventional current flow. Diode Light-emitting diode, LED Photodiode Shotkey diode Transient voltage suppressant diode, TVS Tunnel diode Varicap Zener diode Typical diode packages in same alignment as diode symbol. Thin bar depicts the cathode. Numbering and Coding Schemes There are a number of common standard and manufacturer-driven numbering and code schemes for diodes, The two most common being the EIA-JEDEC standard and the European Pro-Electron standard. EIA-JEDEC The standardized 1N series numbering EIA-370 system was introduced in the U. S. By EIA-JEDEC Joint Electron Device Engineering Council about 1960. Most diodes have a 1-prefix designation, E. G. 1N4003. Among the most popular in this series were 1N34A, 1N270, Germanium signal, 1N914, 1N4148, Silicon signal, 1N400X, Silicon 1A power rectifier, And 1N580X, Silicon 3A power rectifier. JIS The JIS semiconductor designation system has all semiconductor diode designations, Starting with 1S. Pro-Electron The European Pro-Electron coding system for active components was introduced in 1966 and comprises two letters followed by the part code. The first letter represents the semiconductor material used for the component, A equals germanium and B equals silicon, And the second letter represents the general function of the part. For diodes, A equals low power signal, B equals variable capacitance, X equals multiplier, Y equals rectifier, And Z equals voltage reference. For example, AA series germanium low power signal diodes, E. G. AA119, BA series silicon low power signal diodes, E. G. BAT18 silicon RF switching diode, BY series silicon rectifier diodes, E. G. BY127, 1250V, 1A rectifier diode, BZ series silicon zener diodes, E. G. BZY88C4V7, 4. 7V zener diode. Other common numbering coding systems generally manufacturer driven include GD series germanium diodes, E. G. GD9, This is a very old coding system, OA series germanium diodes, E. G. OA47, A coding sequence developed by Mullard, A UK company. Related devices, Rectifier, Transistor, Syristor or silicon controlled rectifier, SCR, Triac, Diac, Varistor. In optics, An equivalent device for the diode, But with laser light, Would be the optical isolator, Also known as an optical diode, That allows light to only pass in one direction. It uses a faraday rotator as the main component. Applications. Radio demodulation. The first use for the diode was the demodulation of amplitude modulated AM radio broadcasts. In summary, An AM signal consists of alternating positive and negative peaks of a radio carrier wave whose amplitude or envelope is proportional to the original audio signal. The diode rectifies the AM radio frequency signal, Leaving only the positive peaks of the carrier wave. The audio is then extracted from the rectified carrier wave using a simple filter and fed into an audio amplifier or transducer, Which generates sound waves via audio speaker. In microwave and millimeter wave technology, Beginning in the 1930s, Researchers improved and miniaturized the crystal detector. Point contact diodes, Crystal diodes, And Schottky diodes are used in radar, Microwave, And millimeter wave detectors. Power conversion. Rectifiers are constructed from diodes where they are used to convert alternating current AC electricity into direct current DC. Automotive alternators are a common example, Where the diode which rectifies the AC into DC provides better performance than the commutator or earlier dynamo. Similarly, Diodes are also used in Cockcroft-Walton voltage multipliers to convert AC into higher DC voltages. Reverse voltage protection. Since most electronic circuits can be damaged when the polarity of their power supply inputs are reversed, A series diode is sometimes used to protect against such situations. This concept is known by multiple naming variations that mean the same thing. Reverse voltage protection, Reverse polarity protection, And reverse battery protection. Overvoltage protection. Diodes are frequently used to conduct damaging high voltages away from sensitive electronic devices. These are usually reverse biased non-conducting under normal circumstances. When the voltage rises above the normal range, The diodes become forward biased conducting. For example, Diodes are used in stepper motor and H-bridge motor controller and relay circuits to de-energize coils rapidly without the damaging voltage spikes that would otherwise occur. A diode used in such an application is called a flyback diode. Many integrated circuits also incorporate diodes on the connection pins to prevent external voltages from damaging their sensitive transistors. Specialized diodes are used to protect from over-voltages at higher power. Logic gates. Diode resistor logic constructs AND and OR logic gates. Functional completeness can be achieved by adding an active device to provide inversion as done with diode transistor logic. Ionization radiation detectors. In addition to light, Semiconductor diodes are sensitive to more energetic radiation. In electronics, Cosmic rays and other sources of ionizing radiation cause noise pulses and single and multiple bit errors. This effect is sometimes exploited by particle detectors to detect radiation. A single particle of radiation with thousands or millions of electron volts of energy generates many charge-carrier pairs as its energy is deposited in the semiconductor material. If the depletion layer is large enough to catch the whole shower or to stop a heavy particle, A fairly accurate measurement of the particle's energy can be made simply by measuring the charge conducted and without the complexity of a magnetic spectrometer, Etc. These semiconductor radiation detectors need efficient and uniform charge collection and low leakage current. They are often cooled by liquid nitrogen. For longer range, About a centimeter particles, They need a very large depletion depth and large area. For short range particles, They need any contact or undepleted semiconductor on at least one surface to be very thin. The back bias voltage are near breakdown, Around 1000 volts per centimeter. Germanium and silicon are common materials. Some of these detectors sense position as well as energy. They have a finite life, Especially when detecting heavy particles because of radiation damage. Silicon and germanium are quite different in their ability to convert gamma rays to electron showers. Semiconductor detectors for high energy particles are used in large numbers. Because of energy loss fluctuations, Accurate measurement of the energy deposited is of less use.

Reviews

I never knew anything about diodes, and I still don’t because I can’t stay awake listening to this! 🤣

Thank you as always, your voice is so soothing! 🤗🥰🤗🥰

What made you think of speaking in a foreign language? Clever technique to bore us to sleep. 😂😴