Diode classification, diode circuit symbols and diode characteristics. A cloud of fog is relative to the novice engineers. So how can a novice engineer quickly increase the knowledge of this piece? Diode circuit symbol and classification, in this small series of electronic technology today to do for the novice engineers to explain the diodes the characteristics of professional knowledge!

(a) the classification of diodes
1, according to the use of the semiconductor materials, can be divided into germanium diode (Ge tube) and silicon diode (Si tube).
2, according to the different purposes, can be divided into detector diode, rectifier diode, zener diode, switching diode, isolation diode, Schottky diode, light emitting diode, silicon power switching diodes, rotating diodes etc..
3, according to the structure of the pipe core, and can be divided into point contact type diode, surface contact type diode and planar diode.
Rectifier diode
The diode is called a rectifier diode, which is the current of the DC current.
The detector diode
Is used for the detector diode superposition in the high frequency carrier frequency signal detected by the device, it has high detection efficiency and good frequency characteristics.
Switching diode
In the pulse digital circuit, the diode is used to switch on and turn off circuit. It is characterized by short reverse recovery time, which can meet the needs of high frequency and ultra high frequency applications.
The zener diode
The zener diode is made of silicon material with diode, it is the use of PN junction reverse breakdown voltage is basically not changed with the variation of current characteristics, to achieve the objective of regulators, because it can play a stabilizing role in the circuit, it is known as the regulator diode (the regulator).
The varactor
The varactor is a nonlinear capacitor using PN junction capacitance with the bias changes made this characteristic, is widely used in parametric amplifier, electronic tuning and frequency multiplier and microwave circuits.
The TVS transient voltage suppressor
A solid state diode, specifically for ESD protection. TVS diode is parallel to the protected circuit, when the transient voltage exceeds the normal operating voltage of the circuit, the diode avalanche, providing access to the transient current, so that the internal circuit from excessive voltage breakdown.
The light emitting diode
With the gap, made of gallium phosphide material with a small volume, a positive driving light. Low voltage, small current, luminous uniform, long service life, which can be red, yellow and green monochromatic light.
Schottky diode
The basic principle is: in the metal (such as lead) and semiconductor (N type silicon wafer) on the contact surface, with the formation of Schottky to block the reverse voltage. The rectification principle Schottky and PN junction have fundamental differences. Its pressure level is only about 40V. Its specialty is: switch speed is very fast: reverse recovery time TRR is particularly short. Therefore, can make the switch and low voltage high current diode rectifier diode.

(two) the circuit symbol of the diode (three) the characteristics of the diode
Through simple experiments, the forward and reverse characteristics of the diode are described.
1 forward characteristic.
In the electronic circuit, the positive electrode of the diode is connected at the high potential end, and the negative electrode is connected to the low potential end, and the diode can lead to the connection mode. It must be explained that when the positive voltage is added to the diode at both ends of the diode, the diode can not be switched on, and the forward current of the diode is very weak.
Only when the forward voltage reaches a certain value (this value is called the "threshold", the Ge tube is about 0.2V, the silicon tube is about 0.6V), the diode is conducting to direct. After the diode at both ends of the voltage is essentially unchanged (germanium tube is about 0.3V, silicon tube is about 0.7V), known as the diode forward voltage drop".
2 reverse characteristics.
In the electronic circuit, the positive electrode of the diode connected to the low voltage, negative pole connected to the high voltage, when the diode almost no current flows when the diode is in the off state, the connection mode, known as reverse bias. When the diode is reverse biased, there will still be a weak reverse current through the diode, called the leakage current. When the reverse voltage at both ends of the diode increases to a certain value, the reverse current will increase dramatically, the diode will lose one direction of conductive characteristics, this state is called the diode‘s breakdown.


From the electronic related article:

　　TVS diode ESD principle and typical circuit cases

　　The use of transient suppression diodes