Diode

Crystal diode is the most basic device in the semiconductor device. It is made of semiconductor single crystal material ( mainly germanium and silicon ), so semiconductor device is also called crystal device. The crystal diode has two electrodes, which is widely used in TV sets, radio cassette recorders and other equipment.

l  Classification of diodes

 ( 1 ) According to the materials

There are some Germanium diodes, silicon diodes and gallium arsenide diodes.

( 2 ) According to the structure, there are some contact diodes and surface contact diodes, etc.

 ( 3 ) Tunnel diode, avalanche diode and varactor are divided according to the working principle.

 ( 4 ) Detect diodes, rectifier diodes and switching diodes by use. Note : now the use of flake diodes is gradually increasing. The chip diode includes rectifier diode, fast recovery diode, Schottky diode, switching diode, zener diode, transient suppression diodes, light-emitting diodes, varactor diodes, and antenna switching diodes.

They are widely used in electronic products and communication equipment.

l  The main characteristics and parameters of the diode

1.The main characteristics of the diode.

The main characteristic of the diode is the unidirectional conductivity.

(1) When the forward voltage is added at both ends of the diode (P is positive, N is negative) very little (the germanium tube is less than 0.1V, the silicon tube is less than 0.5V), the tube is not guided, and the pipe is in the "cut-off" state. After the positive voltage exceeds a certain value, the tube is turned on, the voltage increases slightly, and the current increases sharply. Diodes made of different materials have different starting voltages, with silicon tubes from 0.5 V to 0.7 V and germanium tubes from 0.1 V to 0.3 V.

( 2 ) When reverse voltage is applied to both ends of the diode, the reverse current is very small. When the reverse voltage is gradually increased, the reverse current remains basically the same, the current is called the reverse saturation current. Different materials of the diode, the reverse current size is different, the silicon tube is 1  microamperes to tens of microamperes, and the germanium tube can be as high as hundreds of microamps. In addition, the reverse current is greatly influenced by the temperature change, and the stability of the germanium tube is worse than that of the silicon tube.

 ( 3 ) Breakdown characteristics

When the reverse voltage is increased to a certain value, the reverse current increases rapidly, which is called reverse breakdown. The reverse voltage is called the reverse breakdown voltage. For tubes made of different structures, processes and materials, the reverse breakdown voltage values vary greatly, from 1 V to several hundred volts, even up to a few kilovolts.

( 4 ) Frequency characteristic due to the existence of junction capacitance, when the frequency is high to a certain degree, the capacitive reactance is small enough to short-circuit the PN junction, leading to the loss of unidirectional conductivity of the diode, can't work. The larger the PN junction area is, the bigger the junction capacitance is, the less work can be done in high frequency.

2.The main parameter of the diode

 ( 1 ) The forward current Ip:

allowed to pass the current value of the diode at rated power.

( 2 ) Forward voltage drop Up

the voltage drop generated between the two poles of the  diode through the rated forward current.

( 3 ) Maximum rectified current ( average ) LOM:

allowed the average value of the maximum half-wave current in the case of continuous operation of half-wave rectification.

( 4 ) Reverse breakdown voltage Up:

diode reverse current increases sharply to reverse voltage value when breakdown occurs.

( 5 )Peak reverse voltage UpRM:

Maximum reverse voltage for normal operation of the diode

( 6 ) Reverse current IR:

flows through the reverse current value of the diode at a specified reverse voltage condition.

( 7 ) Junction capacitance C:

junction capacitance includes capacitance and diffusion capacitance. When used in high frequency applications, the junction capacitance is less than a specified value.

( 8 ) Frequency of the highest:

AC signal with unidirectional conductivity at the highest operating frequency f.

If you want to know more, our website has product specifications for the diode, you can go to Allicdata Electronics Limited to get more information.