A transistor is an element designed to amplify, generate, and also convert electrical oscillations. There are two types of transistors: bipolar and field effect.
A bipolar transistor is a semiconductor device consisting of two p-n junctions. An elementary transistor is built on a germanium crystal, it has two tips: an emitter and a collector, which touch the surface of the crystal, separated from one another by a distance of 20-50 microns. In other words, one junction connects the emitter to the base (called the emitter junction), and the second connects the collector to the base (called the collector junction). Bipolar transistors are divided into two types: p-n-p and n-p-n.
A FET is a semiconductor device that is controlled by a change in the field, unlike bipolar elements, where the output current value is determined by a change in the incoming current. Field instruments are available as single-gate and multi-gate.
The circuit diagram of the transistor is shown in the photo below. The scheme of the bipolar element is a short base line, it symbolizes the base, into which two inclined lines enter at an angle of 600 and 1200, a line withthe arrow is the emitter, the second is the collector. The direction of the arrow indicates the type of device. The arrow pointing to the base is a p-n-p type transistor, from the base - n-p-n.
The line perpendicular to the base is the base electrode. The value of the conductivity of the emitter must be known for the correct connection of the transistor to the power source. Devices of the p-n-p type must be supplied with a negative voltage of the transistor to the collector and base, and the n-p-n type must be positive. Field-effect transistors in the diagrams are indicated as follows: it is customary to show the gate with a dash parallel to the channel symbol, the electrical conductivity of the channel is depicted by an arrow placed between the source and drain. If the arrow points in the direction of the channel, then this means that the element belongs to the n-type, and if in the opposite direction, then the p-type. The image of a field effect transistor with an induction channel is distinguished by three short strokes. If the field device has multiple gates, they are depicted as short dashes, the line of the first gate is always placed on the extension of the source line.
In conclusion, we add that such a name was not immediately assigned to transistors, they were originally called semiconductor triodes (similar to lamp technology). So the transistor is a triode, which is a controlled element, it has been widely used in pulse and amplifying circuits. Lack of heat, reliability, small overall dimensions and cost - these are the main advantages of these devices, thanks to which transistorswere able to displace electronic tubes from many branches of technology. The main advantage of semiconductor devices is the absence of an incandescent cathode, which consumes significant power and also takes time to warm up. In addition, the transistor is many times smaller than an electric lamp and is able to operate at a lower voltage. All this made it possible to significantly reduce the dimensions of electronic devices.
