Without exaggeration, it can be argued that the rapid development of electronics began with the invention of the diode. The first came to light vacuum diode lamps.
But they very quickly replaced semiconductor diodes, which proved to be economical, and most importantly - they opened the way for the miniaturization of electronic devices. Given the popularity of these semiconductors, consider the 6 main types of diodes and how they work.
Semiconductor diode structure and principle of operation
The diode consists of two different semiconductors: n-type and p-type to which connected electrodes - an anode and a cathode. The whole structure is enclosed in a metal, glass or plastic housing.
Due to the fact that semiconductors have different types of conductivity (electron and hole) when they contact form p-n transition zone (Fig. 1). On the one hand the positive ions are accumulated, while the other - electrons.
If the cathode is connected to the negative pole of the power source and the anode to the positive, then under the influence of the EMF Recombination of holes occur in the area with n-conductivity, the electrons in the neutralization zone with a p-conductivity.
The barrier between the two semiconductors be destroyed and it closes the circuit. That is, the unit will skip the current from the cathode to the anode (actually, electrons rush to the positive terminal). process scheme is shown in Figure 2a.
When a reverse voltage (Fig. 2 b) the zone of p-n transition will only increase. No current will flow. The diode in this connection will be closed. On this principle work of all rectifier (power) electronic components.
rectifier diodes
This type of electronic valves is most common in power supplies different devices. Diode bridges based on them are used to convert sinusoidal AC to DC.
Depending on the types of the semiconductor materials used, their degree of saturation of various donors and acceptors, semiconductors can change their properties. It is allowed to create various types of semiconductor devices with the required parameters.
zener
A diode that has a high conductivity for a given voltage, the zener diode is called. Upon reaching the level of the zener voltage, it opens and passes a current with almost no resistance. Once the potential difference falls to a predetermined minimum, the Zener otsechot closed and the flow of electrons.
This property is used to stabilize the voltage in electronic devices. Hence the name - a zener diode. One of the most common zener diode is shown in Fig. 4.
tunnel diode
With multiple additives is formed a narrow p-n junction contributes to conduct current in both directions. This feature distinguishes it from other types of valves. In radio circuits of this type are represented as shown in Fig. 5.
varicap
A variation of the variable capacitance diodes called varactors. The barrier capacity of these electronic components is dependent on the inverse voltage.
They are used to adjust the frequency voltage controlled oscillator. Designation of the schemes shown in Fig. 6.
LEDs
They are also called LED or LED. (Fig. 7). These diodes, when forward voltage is applied to electrodes emit a cold light in different spectra. Today, LED-illuminated actively displaces traditional light sources.
photodiode
The conductivity of the conductors of this type is controlled luminous flux. In the dark properties of the photodiode is the same as in the conventional valve. Reverse current is directly proportional to the level of illumination, in Vol. H. infrared. It used as a sensor that receives signals from the remote control.