In this way, diodes have the property of conducting electricity only in a fixed direction. The light-emitting diodes LEDs that we often see in our daily lives are designed to emit light when electricity flows through the PN junction. Diodes are also used in various places where we cannot see them, supporting our daily lives. Date: Relevant technical knowledge What is the role of a Capacitor in Electronic Components?
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Current in AC circuits literally alternates -- quickly switches between running in the positive and negative directions -- but current in a DC signal only runs in one direction.
So to convert from AC to DC you just need to make sure current can't run in the negative direction. A half-wave rectifier can be made out of just a single diode. If an AC signal, like a sine wave for example, is sent through a diode any negative component to the signal is clipped out.
A full-wave bridge rectifier uses four diodes to convert those negative humps in the AC signal into positive humps. DC signals. If you tore apart a wall-wart , you'd most likely see a handful of diodes in there, rectifying it up. Can you spot the four diodes making a bridge rectifier in this wall-wart?
Ever stick a battery in the wrong way? Or switch up the red and black power wires? If so, a diode might be to thank for your circuit still being alive. A diode placed in series with the positive side of the power supply is called a reverse protection diode.
It ensures that current can only flow in the positive direction, and the power supply only applies a positive voltage to your circuit. This diode application is useful when a power supply connector isn't polarized, making it easy to mess up and accidentally connect the negative supply to the positive of the input circuit.
The drawback of a reverse protection diode is that it'll induce some voltage loss because of the forward voltage drop. This makes Schottky diodes an excellent choice for reverse protection diodes.
Forget transistors! For example, a diode two-input OR gate can be constructed out of two diodes with shared cathode nodes. The output of the logic circuit is also located at that node. An AND gate is constructed in a similar manner. The anodes of both diodes are connected together, which is where the output of the circuit is located. Both inputs must be logic 1 forcing current to run towards the output pin and pull it high also. If either of the inputs are low, current from the 5V supply runs through the diode.
Diodes are very often used to limit potential damage from unexpected large spikes in voltage. Transient-voltage-suppression TVS diodes are specialty diodes, kind of like zener diodes -- lowish breakdown voltages often around 20V -- but with very large power ratings often in the range of kilowatts. They're designed to shunt currents and absorb energy when voltages exceed their breakdown voltage. Flyback diodes do a similar job of suppressing voltage spikes, specifically those induced by an inductive component, like a motor.
When current through an inductor suddenly changes, a voltage spike is created, possibly a very large, negative spike. A flyback diode placed across the inductive load, will give that negative voltage signal a safe path to discharge, actually looping over-and-over through the inductor and diode until it eventually dies out. Now that your current is flowing in the right direction, it's time to put your new knowledge to good use.
Whether you're looking for a starting point or just stocking up, we've got an Inventor's Kit as well individual diodes to choose from. See our Engineering Essentials page for a full list of cornerstone topics surrounding electrical engineering. Take me there! Now that you've gotten a handle on diodes, maybe you'd like to further explore more semiconductors:. Need Help? Mountain Time: Shopping Cart 0 items. Product Menu. Today's Deals Forum Desktop Site. All Categories. Development Single Board Comp.
Home Tutorials Diodes Diodes. Contributors: jimblom. Introduction Once you graduate from the simple, passive components that are resistors , capacitors , and inductors, it's time to step on up to the wonderful world of semiconductors. Every electrical project starts with a circuit. Don't know what a circuit is? We're here to help. Favorited Favorite Learn about Ohm's Law, one of the most fundamental equations in all electrical engineering. We can see electricity in action on our computers, lighting our houses, as lightning strikes in thunderstorms, but what is it?
This is not an easy question, but this tutorial will shed some light on it! Learn the basics of using a multimeter to measure continuity, voltage, resistance and current. We've got you covered! Favorited Favorite 75 Wish List. Favorited Favorite 55 Wish List. Favorited Favorite 11 Wish List. Favorited Favorite 5 Wish List. See all diodes. Ideal Diodes The key function of an ideal diode is to control the direction of current-flow. Real Diode Characteristics Ideally , diodes will block any and all current flowing the reverse direction, or just act like a short-circuit if current flow is forward.
Current-Voltage Relationship The most important diode characteristic is its current-voltage i-v relationship. Types of Diodes Normal Diodes Signal Diodes Standard signal diodes are among the most basic, average, no-frills members of the diode family. Favorited Favorite 9 Wish List. Schottky Diode In stock COM Schottky diodes are known for their low forward voltage drop and a very fast switching action.
Favorited Favorite 10 Wish List. Zener Diode - 5. Favorited Favorite 31 Wish List. Diode Applications For such a simple component, diodes have a huge range of uses. Purchasing Diodes Now that your current is flowing in the right direction, it's time to put your new knowledge to good use. Our recommendations:. As you may know, electricity is the flow of free electrons between atoms.
We use copper wires because copper has lots of free electrons which makes it easy to pass electricity through. If we look at a basic model of an atom of a metal conductor, we have the nucleus at the centre and this is surrounded by a number of orbital shells which hold the electrons. Each shell holds a maximum number of electrons and an electron has to have a certain amount of energy to be accepted into each shell. The electrons located farthest away from the nucleus have the most energy.
The outermost shell is known as the valence shell and a conductor has between 1 and 3 electrons in its valence shell. The electrons are held in place by the nucleus. If an electron can reach this then it can break free from the atom and move to another. With an insulator, the outermost shell is packed. Therefore electricity cannot flow through this material. Silicon is an example of a semiconductor. It must be noted however; that as the conduction band is quite close; if we provide some external energy, some electrons will gain enough energy to make the jump from the valance and into the conduction band to become free.
Therefore this material can act as both an insulator or a conductor. Pure silicon has almost no free electrons, so what engineers do is dope the silicon with a small amount of other materials to change its electrical properties. So inside the diode we have the two leads, the anode and the cathode which connect to some thin plates.
Between these plates we there is a layer of P-Type doped silicon on the anode side and a layer of N-type doped silicon on the cathode side. The whole thing is enclosed in a resin to insulate and protect the materials. Each silicon atom is surrounded by 4 other silicon atoms.
Each atom wants 8 electrons in its valence shell but, the silicon atoms only have 4 electrons in their valence shell, so they sneakily share an electron with their neighbouring atom to get the 8 they desire. This is known as Covalent bonding.
When we add in the N-type material such as phosphorus, it will take the position of some silicon atoms. The phosphorus atom has 5 electrons in its valence shell. With P-type doping we add in a material such as aluminium,.
There is therefore a hole created where an electron can sit and occupy. So we now have two doped pieces of silicon, one with too many electrons and one with not enough electrons. The two materials join to form a P-N junction. In this region, some of the excess electrons from the N-type side will move over to occupy the holes in the P-type side. This migration will form a barrier with a buildup of electrons and holes on the opposite sides.
The electrons are negatively charged and the holes are considered therefore positively charged. So the build up causes a slightly negatively charged region and a slightly positively charged region. This creates an electric field and prevents more electrons from moving across. The potential difference across this region is about 0. When we connect a voltage source across the diode, with the anode P-Type connected to the positive and the cathode N connected to the negative, this will create a forward bias and allow current to flow.
The voltage source has to be greater than the 0. When we reverse the power supply so the positive is connected to the N-type cathode and the negative is connected to the P-type anode. The holes are pulled towards the negative and the electrons are pulled towards the positive which causes the barrier to expand, and therefore the diode acts as a conductor to prevent the flow of current. Diodes are represented in engineering drawings with a symbol like the image above.
The stripe on the body is indicated with a vertical line on the symbol and the arrow points in the direction of conventional current. When we look at a diode we see these numbers and letters on the body. These identify the diode so you can find the technical details online. The diode will have an I-V diagram that looks like above. This diagram plots the current and voltage characteristics of a diode which is plotted to form a curved line. This side is how it should perform when acting as a conductor and this side is when acting as an insulator.
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