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By: Mehdi Sadaghdar
0:00 Intro on Diodes
1:24 P-N Junctions make Regular Diodes
3:11 Regular Diode Behavior and Model
7:04 Break Down and Zener Diode
9:05 TVS (Transient Voltage Suppressor diode)
9:56 Photo Diodes
10:24 Solar Panels
10:39 LEDs (Light Emitting Diode)
11:13 Varicap or Varactor
11:59 Schottky Diode

Hi electro boom merti here diodes. What are diodes? They are these brilliant components and brilliant. Well, it's the sponsor of this video, where you can learn a ton of simple to complex, math science and computing concepts with easy to understand. Interactive courses use my link diodes, though there were these massive breakthrough in electronics.

You put four of them together and you get cool bridge rectifier. Imagine! For a long time. We only lived with resistors, capacitors and inductors until we were tired of the linear behavior of impedances and decided to bend the curve diodes. Are these components that allow the current to flow one way and block it from coming back? Basically, there are the check valves of electric current, but how do they work? Well, we don't care at the moment in olden times they started making them out of vacuum tubes, which were pretty much replaced when semiconductors were created.

I placed a link at the corner to a video from mr carlson's lab on vacuum tubes and steve molds video on semiconductors. If you want to learn deeper on how they work here, i just want to surf the surface and talk about what it does. So we can design circuits with it. Silicon diodes are amazing, though you think they just rectify.

Think again, there are millions of different types, maybe around ten, but they are all made based on the same concept. Two different material are fused to each other, and the junction between them has magical properties. Fine, i go a bit deeper. Semiconductors are material typically made of silicon crystal that we doped them with small amounts of impurity and depending on the type of impurity we get positive or negative semiconductors, as their name suggests, they are conductive.

They are electrically neutral, of course, but if we fuse the two types together, the p-type will happily pull electrons from the n-type, which is happy to give them right at the junction. This creates a small region of charge. Imbalance called depletion region. So this means, if we decide to put a positive voltage on the p side and suck electrons out p, gladly takes electrons from n and the negative terminal and current flows with low effort.

But if we flip the voltage across the p-n junction and try to force electrons into p, it won't want to pass electrons into n. That's not their deal. The pn junction blocks the electric current. So we have a diode just try to remember the p and n behavior because it will later help you understand the behavior of all semiconductor components.

P wants to suck electrons from n and n only it doesn't want to suck electrons from the power supply. This is a marriage contract. Only p and n got into diode is generally shown with this symbol like an ato indicating the direction the current can flow, which is the reverse of flow of electrons, and how a reverse current will be blocked by this wall. This is also the symbol of a general purpose: diode you'll see that different type of diodes will have different symbols.
Now, let me show you the ideal behavior of a diode x-axis is the voltage across the diode, and why is the current through it? If the voltage across it tries to get positive or the diode is forward biased, it turns, unlike a switch and lets through any amount of current like a short circuit. But if the voltage is negative or the diode is reversed by us, it blocks, and there is zero current here is a typical through-hole. Diode, you see, the gray line here indicates the direction of the diode. You see.

If i try to put the diode in reverse, the current reading is a bit off, it doesn't conduct and there is no extra current from the power supply. But if i flip the voltage see it is starting to conduct like a short cycle burn. We must not exceed the power rating of the diode, so i'll place, a 10k resistor series to it to limit the current, and now we can measure the voltage and current through the diode for current i'll just measure the voltage across the resistor. I don't know if you can see my resistor and diode in this mess of probes and for my ac power supply.

Of course, i use the power line. It's fine. I put my scope in x y mode x, being the voltage across the diode and y current through it, and it acts like a diode for negative voltages. There is no current and for positive voltages.

It acts like a short circuit. There is current, but no voltage or is it let's zoom in on voltage, see this is a real non-ideal diode. It takes a little bit of voltage before the diode starts, conducting, which is different from diode to diode, and we can assume it to be around 0.6 volts for decent amount of current. But it's actually a little less for a smaller current and a little bit more.

For higher current and after that initial voltage, the current ramps up, so we can approximate a diode's behavior like this, an ideal diode in series with a reverse 0.6 volt ideal battery. We have to overcome and a small series resistance or do like i do when you use a diode, just understand that there is around 0.6 volts across it that can rise slightly when the current rises. We typically ignore this resistance for most applications, because it's small - and we can also ignore this voltage if it is too small compared to the voltages in our application like if they give you this circuit and ask you to calculate the current. You can just assume the diode voltage is 0.6 volts write a kvl as vbat equals resistor voltage, plus the diode voltage or 2 volts is equal, vr, plus 0.6 and vr is equal, ri or equal to 1k times i.

So i is equal to minus 0.6 divided by 1000 or almost 1.4 milliamps, and if they want it, any more accurate tell them to pull the soldering iron out of their butt because nobody writes diode and accuracy in one sentence. Now i change the series resistance to 100k for more precision and, let's zoom in on the current look at that. The current is not zero in reverse voltage. There is a very small leakage current in reverse, so we can add a very large resistor across the diode to model it.
Although the leakage current is typically so small, we can ignore it this time, let's zoom out on the voltage. Look at that the diode. That's supposed to block current in reverse voltage is conducting large amounts of current when the voltage passes above some threshold around 100 volt. In this case, the voltage where current starts flowing is called the breakdown voltage and the region behind.

It is the breakdown or avalanche region. If you push the diode too hard in reverse, it starts conducting that could be destructive to the diode. The reason diode dies here is because you would have very large, reverse voltage and current through it, which results in very large power drop. It heats up quickly and blows up unless you get out of that region very quickly.

That can be modeled with a reverse ideal diode and a battery with breakdown voltage value. You have to be larger in reverse than this voltage for the diode to conduct backwards. We typically ignore this because we keep below that voltage level because that's not a desirable effect until it is, we can make use of breakdown voltage if it is a reliable known voltage, we can use limited current through it and create an almost fixed voltage, typically used As a reference voltage, and so we make something called a zener diode zener diodes are designed to have specific breakdown or zener voltages like 1 volt, 5 volt, 10 volt or whatever in a circuit like this, a zener diode will clamp the voltage close to its breakdown Voltage, regardless of the input voltage well as long as the input is higher than the zener voltage. Here i have a 5 volt zener diode series with some resistance and if i raise the supply voltage, you see the zener and supply rise together until around 5 volts zener starts conducting the supply rises, but the zener voltage is clamped around 5 volts.

Zeners can be used to generate fixed voltages as references or they can be used to protect the circuit against high voltages by clipping the large voltages like this in case of protection. They typically call such diode tbs or transient voltage suppressors, which are much faster to react to transients and are more powerful. A single one called a unidirectional. Tvs like this is placed in reverse on signal lines to clamp over voltage like this.

Two tbs diodes can be combined like this, as one component called bi-directional: tbs that can block the transient high voltage between a positive and negative breakdown voltage, but for regular diodes. We typically ignore all these and usually keep it at this level except well. There is more, the thing is, if you shine a light on the pn junction particles, wiggle harder, sending more electrons from n to p, raising the voltage and affecting the diode's behavior like this diode's body is glass and the voltage across it rises. When i shine a light on it, but we made use of that too, so diodes can be light sensors or, as we call them photosensors did.
I mention they make voltage when we shine light on them. If we play with the chemistry and make them more efficient, we can draw energy from them and we have solar panels renewable energy. Here we come but like steve mold mentioned in his video, if, instead of pulling energy from them, we apply a voltage across them. They create light in infrared now we mess with the chemistry again and make them produce visible light, and we have leds efficient lighting.

Here we come the only difference between leds and regular. Diodes is well beside the fact that they generate visible light that their forward voltage drop is larger depending on their color, otherwise they could also be used as a poor man's regular dial. Oh and remember when i said a diode blocks, reverse current. If you look at the pn junction there, the depletion layer acts like a thin layer of insulation, so the diode acts like a capacitor holding charge.

The width of depletion layer depends on the reverse voltage, which means adjusting the reverse voltage. You can change the capacitance, a variable capacitance, based on the voltage across it. You design it better for this purpose and you get a battery cap or validactor tuning the capacitance with voltage. You can create, for example, an adjustable frequency generator, maybe to make an fm transmitter.

Semiconductor diodes man, they change the world, but mostly when we say diode, we are referring to the regular current rectifying diode or its cousin shot key diode, which has a much faster response time and lower forward voltage, so less power loss, but has a larger reverse leakage. Current mostly used in switching power applications, there are other type of diodes. I care less about what i care more about, though, is brilliant the sponsor of this video, brilliant man, just brilliant. It's an awesome tool for learning simple to complex stem concepts of math science and computing easily.

That's where i would go to remember all those things that vaporized from my brain or to learn new stuff. Why? Because they made courses like james and puzzles and fun a ton of interactive courses and quizzes to teach you what you would need for your school job or interview like their brand new everyday math course. Where they break down foundational math. You would need for everyday life to more advanced courses like neural networks, special relativity and such so all ages and levels can learn well with all those interactivity give yourself and your family.

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7 thoughts on “Diodes! all sorts of them and how they work electroboom101-010”
  1. Avataaar/Circle Created with python_avatars Scott's Synth Stuff says:

    One of your best videos to date, Mehdi. I've been doing electronic design for years, and knew most of the uses and properties of diodes, but did not know WHY they behaved the way they did. I learned a ton!

  2. Avataaar/Circle Created with python_avatars mikethor009 says:

    Awesome video as always!

  3. Avataaar/Circle Created with python_avatars Nicola Domini says:

    We want the full song between sections!

  4. Avataaar/Circle Created with python_avatars Hola! Laura Edmunds says:

    Editings skills are getting too powerful

  5. Avataaar/Circle Created with python_avatars Virtlink says:

    You should demonstrate a Full Bridge Rectifier using LEDs. Can you actually see the current path change, perhaps using a lower frequency than main's voltage?

  6. Avataaar/Circle Created with python_avatars eloniusz says:

    Engineer: "Huh, the diode produces an insignificantly small electrical current when I shine a strong light at the PN junction."
    Normal person: "Yeah, yeah. That's neat but could you do something useful instead of playing with your electronic toys?"
    Engineer: "…I wonder what would happen if I make the PN junction as big as the roof of my house."
    I love engineers!

    I thought I can't learn anything from a video about something as simple as diodes but here we are. Finally I get why there is so many symbols for them … and that neighbors don't try to steal out sun with those big rectangular things.

  7. Avataaar/Circle Created with python_avatars The2x4 says:

    Always love the vids! Great knowledge, making me feel brilliant once you finish explaining!
    Also, you just got me a 3D printer, so I'm an even bigger fan than before!!! 😀

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