What does the directivity of a diode mean? How to measure

Forward conduction, reverse non-conductive.

1. Forward characteristics.

In electronic circuits, the positive pole of the diode is connected to the high potential end and the negative terminal is connected to the low potential end, and the diode will be turned on, and this connection method is called forward bias. It must be noted that when the forward voltage applied to both ends of the diode is very small, the diode still cannot be conducted, and the forward current flowing through the diode is very weak. Only when the forward voltage reaches a certain value (this value is called the "threshold voltage", which is about germanium and silicon), can the diode be turned on straight.

The voltage across the diode remains essentially the same after turn-on (about germanium tubes, about silicon tubes, and is called the "forward voltage drop" of the diode).

2. Reverse characteristic.

In electronic circuits, the positive pole of the diode is connected to the low potential end, and the negative terminal is connected to the high potential end, at this time there is almost no current flowing through the diode, and the diode is in a cut-off state at this time, this connection method is called reverse bias. When the diode is in reverse bias, there is still a weak reverse current flowing through the diode, which is called leakage current. When the reverse voltage at both ends of the diode increases to a certain value, the reverse current will increase sharply, and the diode will lose its unidirectional conductivity, which is called the breakdown of the diode.

Test the quality of the diode.

Beginners can use a multimeter to test the diode performance in amateur conditions. Before testing, turn the transfer switch of the multimeter to the RX1K gear of the ohm gear (be careful not to use the RX1 gear, so as not to burn out the diode due to excessive current), and then short-circuit the red and black meter pens to zero in ohms. 1. The positive characteristics test puts the black pen (positive pole in the table) of the multimeter to the positive pole of the diode, and the red pen (negative pole in the table) to the negative pole of the diode.

If the watch hand does not swing to the 0 value but stops in the middle of the dial, the resistance value at this time is the forward resistance of the diode, and generally the smaller the forward resistance, the better. If the forward resistance is 0, it means that the die is short-circuited and damaged, and if the forward resistance is close to infinity, it means that the die is broken. Neither short nor open circuits can be used.

2. The reverse characteristic test touches the positive pole of the diode with the red watch pen of the million and table, and the black watch pen touches the negative pole of the diode, if the watch hand points to the infinity value or close to the infinity value, the tube is qualified.

Directionality is unidirectional, the diode is a pn section, the p pole is connected to the positive pole, the p pole is connected, and the reverse pole is connected, that is, the n pole is connected to the positive pole, which is not on.

The method of judging the positive and negative poles of the diode is as follows: 1. For ordinary diodes, the surface of the body can be seen as nonsense, and the end of the white line is the cathode. 2. For light-emitting diodes, the long pin is the positive pole and the short pin is the negative pole.

3. If the pins are cut to the same length, the smallest metal in the LED tube is the anode, and the large metal piece is the cathode. 4. If you can't see clearly, you can also turn on the multimeter, turn the knob to the on-off position, and connect the red and black probes to the two pins respectively. If there is a reading, one end of the red stylus is positive, and if there is a reading of 1, one end of the black stylus is positive.

A diode is an electronic device made of semiconductor materials (silicon, selenium, germanium, etc.). ), which has unidirectional conductivity, that is, when a DC voltage is applied to the anode of the diode, the diode is turned on. When the reverse voltage is applied to the anode and cathode, the diode is turned off.

So the on/off of the diode is equivalent to the on/off of the switch. Diode structureThe diode is encapsulated by a p-n junction, corresponding electrode leads and shells, and uses different doping processes. By diffusion, p-type semiconductors and n-type semiconductors are made on the same semiconductor (usually silicon or germanium) substrate, forming a space charge region at their interface, called a p-n junction.

A diode has two electrodes, and the electrode that leads out of the p-region is the positive electrode, also called the anode. The electrode that emerges from the n-region is the negative electrode, also known as the cathode, and the character symbol of the diode is represented by VD. Due to the unidirectional conductivity of the PN junction, when the diode is turned on, the current direction is from the anode through the tube to the cathode.

The main principle of the diode is to use the unilateral conductivity of the PN junction to add leads and packages to the PN junction to form a diode.