Types of Diodes - The Learning Circuit

the following program is brought to you by element14 the electronic design community where you can connect and collaborate with top engineers from around the world join now at element14.com hi and welcome back to the learning circuit where we learn about basic electronics today we're going to talk about diodes diodes are semiconductor components that allow electric current to flow in one direction but not the other in a previous episode we discussed how PN junctions work let's review PN Junction diodes and talk about how they differ from other common diodes these are considered your typical diodes they have a PN Junction with a threshold voltage that has to be reached before current will flow through them in silicon diodes this is 0.7 volts once this is reached the current will flow flow flow when hooked up backwards in reverse bias these diodes do not allow current to flow there like Gandalf you shall not pass however like gandalf against the Balrog they can be defeated when connected in reverse bias if supplied with too much voltage more than their breakdown voltage the diodes will break down and allow current to flow in the wrong direction and while Gandalf came out looking pretty cool we're not so lucky with diode the white witch got that way because it overheated sad broken diode well we'll talk more about breakdown voltages again a little bit later Schottky diodes often look like typical diodes but unlike PN Junction diodes Schottky diodes have a metal semiconductor Junction in a previous episode we talked about how PN junctions have a depletion zone it shrinks when connected in forward bias and grows when connected in reverse bias in some circuits the direction of current is intentionally switched between forward and backward rapidly silicon diodes require time for their depletion zone to grow and shrink when switching from allowing forward current it's a blocking reverse current there's a recovery time Schottky junctions have no depletion zone because of their metal semiconductor Junction Schottky diodes have virtually no recovery time and therefore have much faster switching speeds this means they can handle switching current better and faster which makes them useful in high frequency applications they also have a lower forward voltage drop silicon diodes have a voltage drop of around 0.7 volts but the voltage drop of Schottky diodes is between 0.15 volts and 0.46 volts this means they lose less energy to heat making them more efficient Schottky diodes are not useful in all applications though while silicon diodes allow little to no current to flow backwards through them Schottky diodes can leak a small amount of current backwards this can cause problems in certain circuits let's talk about Zener diodes Zener diodes unfortunately also look like typical and Schottky diodes they're really not making it easy for us while Schottky diodes can let some voltage leak through backwards Zener diodes are actually designed to allow current to flow in both directions kind of seems like they're missing the point of being a diode but let's see how current flows through them to see why that could be useful in forward bias Zener diodes function just like any other diode we talked about how typical diodes have a breakdown voltage in reverse bias if the breakdown voltage is exceeded the diode is damaged but Zener --zz have a special heavily doped PN Junction that allows only a certain voltage through and without damaging the diode this happens at a specific voltage the Zener voltage in reverse bias current will not flow through until the Zener voltage is reached but also the voltage will be limited to the Zener voltage for example a 3.3 volt Zener diode will not allow current to flow until the supply voltage reaches 3.3 volts so if it's applied with 2 volts no current flows however this diode could be supplied with 5 6 9 12 volts and it will regulate the voltage output to 3.3 volts so it's kind of like having two diodes in one package but one face is one way and the other faces the other way zena's can have Zener breakdown voltages of anywhere from 1.8 volts all the way up to 200 volts the next and probably most recognizable diodes are LEDs light emitting diodes LEDs use the energy from the particles moving through the PN Junction to create light they can do this because they are made with gallium arsenide unlike silicon diodes diodes made with gallium arsenide release energy in the form of light or photons like other diodes they typically have two leads though these can vary in length depending on the manufacturer I've gotten stuck with short leg LEDs which can make some projects tricky so beware LEDs come in a wide variety of packages through-hole LEDs can be three millimeter five millimeter ten millimeter they can have round and square lenses lenses can be clear or colored if you're looking for the most common through-hole LEDs it would probably be these five millimeter round ones they're pretty popular with hobbyists surface mount LED has come in a variety of sizes as well here are some examples when choosing an LED one of the first things you'll look for is color or wavelength here's our chart of the color spectrum at the bottom you can see the wavelengths that correspond with each color 400 nanometers to 700 nanometers looking for just a blue LED might not be enough you can often find a range of each color to choose from blue could be 445 nanometers or 480 nanometers or anything in that area of the spectrum another choice you'll have is beam angle or viewing angle beam angle is the amount of degrees where the light is visible depending on your application you may want a narrow beam angle like 10 degrees or a wide beam angle like a 120 degrees where common light bulbs are measured in watts or lumens the brightness of LEDs can be found as luminous intensity and is measured in Millikan Della's or MCD the higher the number the brighter the light a standard LED could have a luminous intensity of seven milik and ellas whereas a super-bright led could be 120 milli candelas LEDs can have a range of voltage and current readings they have both a minimum voltage and current required to function properly or even at all as well as a maximum voltage and current that if surpassed could shorten the life of the LED or burn it out completely it's important to get this information off of the component data sheets so you know how much resistance you'll need to add depending on what voltage you are using in your circuit while LEDs emit incoherent light laser diodes emit high-intensity coherent light they do this by having API N or pin junction rather than the standard PN Junction the pin Junction has the standard p-type and n-type regions we're familiar with but between them there is an area of undoped or intrinsic semiconductor at the junction in that intrinsic layer is where all the magic happens when current flows through the diode energy is released in the form of photons or light into that intrinsic layer but it doesn't stop there in a laser diode the P and n-type regions have polished reflective ends which causes the photons to reflect back and forth hundreds of times in that intrinsic layer the photons eventually escape in the form of a laser beam you can frequently see where a laser hits a surface but you can't always see the laser beam itself if you can see the laser beam be extra careful that's a high-powered laser and it has the potential for causing permanent eye damage while LEDs and lasers emit light photodiodes sense light light has these energy particles called photons when light hits the PN junction of a photodiode energy from the photons is transferred to the diode and creates free electron and hole pairs remember what happens when a diode is in reverse bias mode the changes in the junction repel the holes towards the anode and the electrons towards the cathode this usually restricts the flow of current in this case energy is being introduced by way of the photons so a current is created in reverse bias mode this is called the photoelectric effect and the photodiode is considered to be in photoconductive mode photo diodes can also be used in zero bias or photo voltaic mode this is where the current is restricted and so the electron hole pairs and therefore the voltage builds up that kind of sounds like a solar cell doesn't it well they are very similar except photo diodes are designed to be sensors or receivers and convert light into signal whereas solar cells are designed to convert light into power one last thing to note is that a photo diodes response time gets slower the larger the photodiode gets there are a ton of uses for diodes diodes can be used as rectifiers meaning they can convert AC voltages into DC voltages so rather than running off of batteries you can plug right into the wall they can be used to regulate current for voltage protection controlling signals if you remember the heck Manjhi game we made on the Ben Heck show diodes can be used to create logic gates LEDs are becoming more popular and cost effective quickly replacing most old forms of light bulbs and lighting applications lasers aren't just for pointing at the wall in teasing your cat they're used to read and record CDs DVDs and blu-ray discs they're what make barcode readers work they're used in printing and scanning fiber-optic communications rangefinders technology has come so far that lasers can be used in surgery and be more accurate than a surgical knife I've covered the more common types of diodes but there are still other types and endless uses I haven't covered if you have more information you'd like to share on this topic or if you have a question about diodes please post those only element14 community on element14.com /the learning circuits happy learning [Music]

Channel: element14 presents

Views: 46,927

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Keywords: electronics, hardware, gaming, hacking, mods, weekly, element14, madison, wisconsin, maker, engineering, circuit, battery, switches, diodes, logic, photodiodes, thelearningcircuit, blue led, gallium arsenide, laser diodes, tlc, stem_projects, green led, purple led, white led, light emitting diodes, schottky diodes, zener voltage, pin junction, p-i-n junction, p-n junction, silicon diodes, zeners, p-n junction diodes

Id: ABBOR1qqRFI

Length: 10min 41sec (641 seconds)

Published: Wed Oct 10 2018