As a result, a diode typically conducts electricity in just one direction. When you put an electrical gadget or appliance into a standard wall outlet in your home, you are using 110 volts of alternating current (AC). Rectifiers, such as diodes, are used to convert alternating current (AC) to direct current (DC). The most common type of diode is the photodiode, which becomes illuminated when exposed to light.
However, there are other types of diodes that can be used for rectification. Zener diodes may be used in circuit protection applications where a high voltage must be prevented from reaching a sensitive area of the circuit. Their small size makes them good choices for integrated circuits. Bipolar junction transistors (BJTs) can also be used for rectification purposes. However, since they operate based on the behavior of silicon p-n junctions, they are more accurate than diodes and less prone to failure due to age or degradation of quality control during production.
Photodiodes were originally invented by Bell Labs in 1947. They are actually modified silicon phototubes that have been integrated onto a single chip. Photodiodes are used in many modern electronic devices including digital cameras, cell phones, and photocopiers. They are also found under many other names, such as PIN diodes, MOS diodes, or Schottky diodes.
Diodes only conduct when they are forward biased. Because the alternating current flips its direction on a regular basis, the diode conducts only half of its cycles and insulates the other. This diode feature is exploited in the rectification of AC into DC. Two diodes (for a center tap rectifier) or four diodes are utilized in that situation. The reverse-biased diodes do not conduct and so do not waste energy.
The diagram below shows how two diodes can be used to make an electrical center tap. In this example, D1 and D2 are silicon diodes while S is a silicon switch. Note that D1 and D2 must be reversed bias during part of the cycle if you want them to conduct at the same time.
Here's how it works. First, note that both diodes are reversed bias at the beginning of the cycle. Thus, neither will conduct until something causes them to go forward bias at the same time. This will happen at the top of the waveform when V+ is high and V- is low. The diodes will then both conduct, allowing current to flow through their shared path to the center tap and back into each terminal.
At the bottom of the waveform, V+ is low and V- is high. So now both diodes are forward biased and will continue to conduct until something causes them to stop at the same time.
Thus, under forward bias situations, the diode enables current and blocks current in reverse bias conditions. In layman's terms, a diode permits current to flow in just one way. The diode's one-of-a-kind feature allows it to function as a form of rectifier, converting alternating current to direct current.
There are two types of diodes: N-type and P-type. An N-type diode will conduct current in the direction from the anode to the cathode when applied with forward voltage, while a P-type diode will conduct current in the opposite direction when subjected to forward bias.
Diodes are widely used in power applications where you need something that will only allow current to flow in one direction. They can also be used in circuits where linearity is important; for example, audio signals require linear amplification because otherwise noise would be added to the signal.
The diode itself is made up of two layers of atoms bonded together. When light strikes one side of the diode, electrons are released which create a negative charge on the layer. These electrons have no place to go so they jump across the junction into another part of the diode where there is an accumulation of positive charge. This is how current flows through the diode from anode to cathode.
Diodes can be damaged by excessive current or voltage, heat, light, and mechanical stress.
A diode is a device that permits current to flow in just one direction. This is accomplished by the use of a built-in electric field. There are two types of diodes: forward-biased and reverse-biased.
Diodes are used in many circuits within an electronic device. For example, they are used to control what direction current flows through a circuit. Current will only flow through either the LED or the NPN transistor, but not both. This is because electrons are flowing from the collector to the emitter of the transistor, while holes are flowing from the base to the emitter. Only certain materials can conduct electrons, such as gold, silver, copper, and aluminum; others conduct holes, such as nichrome and carbonized cotton. By placing a diode in series with the LED, the current can now flow from the positive terminal of the battery to the negative terminal. This is called forward biasing the diode.
In order for the transistor to turn on, current must be able to flow into its base from some source. This could be another PNP transistor, an inductor (which will be discussed in more detail later), or even directly from the battery if there is enough voltage across it.
A diode's cathode (negative terminal) is connected to a voltage source with nothing connected to its anode (positive terminal). Current will flow from the voltage source into the diode, but not out of it. The circuit needs to be reversed before current can flow again.
Diodes are used in many circuits requiring selective current flow. For example, diodes are used to complete the circuit when building a self-powered sensor such as a smoke detector or an intruder alarm. Also, diodes are used to control what happens in a circuit when another part of the circuit is activated. For example, if you have a radio receiver and want to hear music instead, a diode can be used to divert current away from the speaker so that it doesn't burn up your radio. Diodes are also used to protect other components in the circuit from high voltages that may otherwise damage them. For example, if you have a meter that displays volts across some component, a diode can prevent any voltage more than about 0.6 volts from appearing on the meter's face.
Diodes come in several different types for various applications.