What is a triode? What is the classification and working principle of triodes?Easy to understand the triode, it turns out that it works like thisA triode, that is, a semiconductor triode, is a semiconductor device that controls current. Its function is to amplify a weak signal into an electrical signal with a large amplitude value, and it is also used as a non-contact switch. Usually, the triode has the function of current amplification. Its structure is to make two PN junctions close to each other on a semiconductor substrate. The two PN junctions divide the whole semiconductor into three parts, the middle part is the base region, and the two measuring parts are the emission part. There are two kinds of PNP and NPN according to the arrangement on both sides.The two PN junctions of the triode are similar to two common cathode or common anode diodesCut-off state: the voltage of the emitter junction of the triode is less than the turn-on voltage of the PN junction, the base current is zero, the collector current and the emitter current are both zero, the triode loses the current amplification effect at this time, and the collector and the emitter are quite equal. For the off state of the switch, we call the transistor in the cut-off state.Amplified state: When the voltage applied to the emitter junction of the triode is greater than the turn-on voltage of the PN junction, the emitter junction of the triode is forward biased, \u041c\u043e\u0434\u0443\u043b\u044c \u0441\u0432\u044f\u0437\u0438 CAN2.0 and the collector junction is reverse biased. At this time, the base current controls the collector current. Make the triode have a current amplifying effect.Saturated conduction state: when the voltage applied to the emitter junction of the triode is greater than the conduction voltage of the PN junction, and when the base current increases to a certain extent, the collector current no longer increases with the increase of the base current, Instead, it does not change much near a certain value. At this time, the triode loses the current amplification effect, the voltage between the collector and the emitter is very small, and the gap between the collector and the emitter is equivalent to the conduction state of the switch. This state of the triode is called the saturated conduction state.Amplify weak signals: a small signal input to the base will cause a large current change in the collector, which is one of the most important and core parts of electronic circuits.Used as a non-contact switch: use the cut-off and conduction characteristics of triodes to control or drive loads; such as gate circuits composed of triodes, switching power supplies, etc.There are many types of triodes, according to different categories can be:\u2460Semiconductor materials are divided into: silicon tube and germanium tube;\u2461 According to the working frequency:\u0410\u043d\u0442\u0435\u043d\u043d\u0430 \u0438 \u043f\u0438\u0442\u0430\u043d\u0438\u0435\u041c\u043e\u0434\u0443\u043b\u044c \u043f\u0438\u0442\u0430\u043d\u0438\u044f there are low-frequency tubes and high-frequency tubes;\u2462 According to the power: there are small power tubes, medium power tubes and high power tubes;\u2463 According to function: divided into switch tube, power tube, Darlington tube, photosensitive tube, etc.