A transistor is a small electronic device containing a semiconductor and having at least three electrical contacts, used in a circuit as an amplifier, detector, or switch. It is the fundamental component of most active electronic circuits, including digital electronics. The transistor was invented on 1947-12-23 at Bell Labs. There are two kinds, the bipolar transistor (also called the junction transistor), and the field effect transistor (FET). Transistors and other components are interconnected to make complex integrated circuits such as logic gates, microprocessors and memory.
How a FET transistor works?.
The field-effect transistor (FET) controls the current between two points but does so differently than the bipolar transistor. The FET operates by the effects of an electric field on the flow of electrons through a single type of semiconductor material. This is why the FET is sometimes called a unipolar transistor. Unlike bipolar semiconductors that can be arranged in many configurations to provide diodes, transistors, photoelectric devices, temperature sensitive devices and so on, the field effect is usually only used to make transistors, although FETs are also available as special-purpose diodes, for use as constant current sources. .
Current moves within the FET in a channel, from the source connection to the drain connection. A gate terminal generates an electric field that controls the current. The channel is made of either N-type or P-type semiconductor material; an FET is specified as either an N-channel or P-channel device. Majority carriers flow from source to drain. In N-channel devices, electrons flow so the drain potential must be higher than that of the Source (VDS > O)- In P-channel devices, the flow of holes requires that VDS < 0. The majority carriers of the channel, ordinarily positive for P-channel FETs and negative for N-channel FETs, determine the polarity of the electric field that controls current in the channel.