To understand what a transistor is for, this analogy will best help: if a small cell is a brick in a living organism, then a transistor is a brick in the digital revolution. Without it, all the technological wonders that we use every day (mobile phones, computers, cars) would be significantly different from modern ones, or even would not exist at all.
Content
- Historical overview
- Simplified scheme of work
- Basic structure
- Types and types
Historical overview
Before semiconductor elements of electrical circuits were invented, designers used vacuum tubes and mechanical switches for the same purposes. The lamps were far from ideal. They needed warming up before starting work, they could not boast of reliability, unreliability and compactness, they consumed too much energy. All appliances, from televisions to early computers, were based on them.
After World War II, scientists actively searched for an alternative to lamps and found the answer in the works of Julius Lilienfeld in the late 1920s. This Polish-American physicist has filed a patent for a three-electrode device made of copper sulfide. Unfortunately, there is no evidence that he actually made a working device. But his research helped create what is today called a field effect transistor.
Twenty years after Lilienfeld, Bell was in dire need of something better than lamps for their communications systems. She gathered a stellar team of scientific minds to work on the study of substitutes for vacuum elements, among the group were:
- John Bardeen;
- Walter Brattain;
- William Shockley.
In 1947, Shockley was director of transistor research at Bell, Brattain was an authority on solid state physics, and Bardeen was an electrical engineer and physicist. They experimented successfully with germanium for a year, and soon after, Shockley refined their ideas by developing a transistor junction. The following year, Bell announced to the world that it had invented a working semiconductor triode. In 1956, a team of scientists received the Nobel Prize in Physics for this discovery.
Understanding the scale of the invention and why transistors are needed is impossible without realizing this fact: these small devices have made one of the biggest technological leaps forward humanity. And this is no exaggeration - they really changed the course of history.
Simplified scheme of work
Transistors are devices that control the movement of electrons, and therefore electric current. To understand what a transistor does, the analogy with a water tap and fluid flow is best suited, but, in unlike the latter, they not only can pass or block the flow, but are also able to control it number. The use of transistors is extremely wide and is based on the fact that as an electronic component it can perform two different functions:
-
Amplifier. In this capacity, it accepts small electric currents at one terminal and creates significant currents in the output circuit. This property is used in electronics to amplify signals, thanks to which transistors have replaced tube triodes. - Switch. Depending on the presence or absence of a signal at the control electrode, it is able to close or open the circuit. This is how computer chips work. For example, a memory chip contains hundreds of millions or even billions of transistors, each of which can be controlled on or off. Since all of them in the scheme are in only one of two states, they can be the custodians of binary information - zero or one. A chip of billions of transistors is capable of storing billions of zeros and ones.
Basic structure
Case, insulation, semiconductor crystal, metal leads - this is what a transistor consists of. Different doping of a semiconductor allows you to create two types of its structure:
- p-type;
- n-type.
The crystal itself is a sandwich of these two types, arranged so that two identical layers of the sandwich contain opposite ones. Depending on their combination, the transistor is called either the p-n-p or n-p-n type. The names of the three pins connected to the corresponding layers are common to all types of bipolar and field transistors, respectively, and reflect their purpose (the terms used in relation to field-effect are indicated in brackets):
- base (shutter);
- collector (drain);
- emitter (source).
The base (gate) receives a weak control signal, and a strong collector current (from source to drain) flows between the other two pins. The latter changes depending on the base current. Outwardly, the transistor looks like a radio-electronic component with three terminals.
Types and types
The timing of the invention of transistors was not accidental. Their crystals require pure semiconductor materials to function properly. It was after World War II that the progress of technology in obtaining germanium, as well as advances in the field alloying made it possible to obtain materials suitable for serial production of semiconductor devices.
Later, silicon was used instead of germanium in commercial electronics. Semiconductors based on it are more reliable and affordable than germanium. Silicon is suitable for computer manufacturing. In chips, transistors are not isolated as separate components, but are part of what is called an integrated circuit, and are located on a single semiconductor crystal together with other elements - capacitors and resistors. Modern silicon devices in a microchip are so small that their dimensions are measured in nanometers.
The evolution of materials for the manufacture of these devices does not stand still. Thanks to recent advances, a material called graphene may become the basis of triodes in the 21st century. It carries electrons much faster than silicon, and could form the basis of computer chips that are orders of magnitude more efficient than silicon-based semiconductors.
What transistors are like is not limited to their division according to the crystal material. There are two large groups that differ in management methods:
- field;
- bipolar.
The word "field" means that the gate is controlled by an electric field, that is, to change the current between the drain and the source, it is enough to change the voltage. And in bipolar reactions, the collector current is achieved by changing the current at the base. Bipolar devices were massively used in the 1960s and 70s and are in demand in our time as elements of analog circuits mainly due to the fact that they are easy to manufacture and have a large linearity. The field has captured almost the entire market share of digital circuits.
There are other types of transistors. They are cataloged not only by the principle of operation, but also by power, operating frequencies, structure, application and other indicators. The development of these devices continues without slowing down. For example, scientists from South Korea have recently created a p-n junction made from a single benzene molecule. Chips today generate a lot of wasted heat. In this regard, molecular transistors may have a great future - they can become the key to improving energy efficiency.
Regardless of the directions in which the development of technologies will be carried out, it is obvious that thanks to active research ways to improve transistors, computers will become faster, cheaper and more reliable, and cell phones - even lighter and more compact. These small devices continue to reshape the technological landscape and ultimately our society as a whole. This is a wonderful fate for a simple device invented over 60 years ago.
