Understanding Electronics: Semiconductors, Diodes, and Transistors
The Basics of Electronics
The fundamentals of electronic technology are closely related to the behavior of electrons and various phenomena. The field of electronics, divided into multiple disciplines, has experienced rapid development in this century. Electronics has played a crucial role in this advancement, starting with vacuum tubes, then diodes and transistors, and subsequently with integrated circuits and microprocessors.
Semiconductors
Semiconductors are materials with properties between those of good conductors and insulators. While they are insulating materials, they allow the passage of electrical current under certain conditions. There are two main types:
- Intrinsic Semiconductors: These are formed from a single basic component, typically germanium or silicon.
- Extrinsic Semiconductors: Semiconductors inherently have very low electrical conductivity. To increase conductivity, impurities are added to the material’s lattice, making it easier for current to flow. This results in an extrinsic semiconductor.
The Diode
A diode is essentially formed by two semiconductors, P and N, joined together and encapsulated. The terminal connected to the P-type semiconductor is called the anode (a), and the terminal connected to the N-type semiconductor is called the cathode (k).
Diodes can perform various functions, with their use as a rectifier being the most notable in the industry. When a diode is energized so that the anode is positive with respect to the cathode, it is said to be forward biased. In these circumstances, it behaves like a closed switch and allows current to flow. When the anode is negative with respect to the cathode, the diode is reverse biased, and no current passes.
Phase Rectifier
Electronic circuits require a power source that supplies direct current (DC). However, the electrical power available in the current network is alternating current (AC). Therefore, there is a frequent need to obtain DC from AC, and a rectifier must be used.
The Transistor
Discovered by researchers at Bell Telephone Laboratories in 1948, the transistor quickly became widely used, significantly boosting electronic engineering. A transistor is formed by two PN junctions.
Transistors can be independent components with three pins connected to other circuit components, or they can be integrated into a chip. Transistors are present in almost all electronic circuits that perform functions such as automatic control, signal amplification, calculators, and radio signal processing.
Bipolar Transistors
A bipolar transistor is an electronic device consisting of three blocks of extrinsic semiconductor material, encapsulated with three terminals for connection.
Bipolar transistors operate in three regions:
- Saturation: The transistor behaves like a closed switch between two of its terminals when the appropriate signal is applied to the third terminal. It acts as a small power relay.
- Cut-off: This is the opposite of saturation. No signal on one terminal electrically isolates the other two terminals, serving as an open switch.
- Amplification: A small analog variable signal causes a larger, more powerful signal.