What is a transistor? The structure of the transistor
A transistor is a solid semiconductor device. It has multiple functions such as detection, rectification, amplification, switching, voltage regulator, and signal modulation. As a variable current switch, the transistor can control the output current according to the input voltage. Unlike traditional mechanical switches (such as relays, switches), transistors use telecommunication signals to control their opening and closing, and the switching speed can be very fast, for example, the switching speed in the laboratory can be higher than 100GHz. Strictly speaking, a transistor refers to all single components based on semiconductor materials, including diodes, transistors, field effect transistors, silicon control, etc. In addition, transistors usually refer to transistors.
Transistors are divided into two main categories: bipolar junction transistors (BJT) and field effect transistors (FET).
The transistor has three poles. The three poles of a bipolar junction transistor are composed of emitter (consisting of N-type and P-type), base and collector respectively. For field effect transistors, they are source, gate and drain respectively.
Because transistors have three polarities, there are also three ways to use them, namely emitter grounding (called common emitter amplification, CE configuration), base grounding (called common base amplification, CB configuration), and collector grounding (Referred to as common set amplification, CC configuration, emitter coupling logic).
Transistors are semiconductor devices, usually used as amplifiers or electronically controlled switches. Transistors are important components that regulate the operation of computers, mobile phones, and all electronic devices. Because of its high response speed and accuracy, transistors can be used in a variety of digital and analog functional designs, including amplifiers, switches and regulators, signal modulation and oscillator circuits. The transistors can be packaged individually or in a very small area that can accommodate 100 million or more transistors integrated into a part of the circuit.
Transistor structure and operation
Transistors are made by stacking three layers of different semiconductor materials. Some of these layers add extra electrons, called “doping”, while other layers remove electrons (doping with “holes”-that is, no electrons). The semiconductor material with extra electrons is called N-type (negative electrode), and the material that removes electrons is called P-type (positive electrode).
With some hand waving, we can say that electrons can easily flow from the N zone to the P zone if they have a little force (voltage) to push them. But the flow from P zone to N zone is very difficult (more force and voltage are required).
NPN transistors are designed to pass electrons from the emitter to the collector (traditional current flows from the collector to the emitter). The emitter emits electrons to the base, and the base controls the number of electrons. In fact, most of the emitted electrons are “collected” by the collector, which sends them to the next part of the circuit.
PNP has a small special area. The base still controls the current, but the current flows in the opposite direction, that is, from the emitter to the collector, instead of electrons, the emitter emits the “holes” collected by the collector.
Transistors are a bit like electronic valves. The base pin is probably a handle, and you can adjust it to allow more or less electrons to flow from the emitter to the collector.