Last Updated on October 22, 2023 by Kevin Chen
Image source: Online science notes
Transistors and vacuum tubes are two common electronic devices that are found in many electronic devices and are used for almost similar reasons. You will find them in computers, automotive devices, industrial equipment, home appliances, and communication devices among many other electronics.
The fact that they tend to perform the same functions can easily confuse one. You may assume that they are the same yet in reality they are completely different. In this article, we are going to have a complete breakdown of the differences between transistors vs vacuum tubes. At the end of it, you will know which one is more suitable for your application area.
What is a transistor?
A transistor is a common semiconductor device whose structure comprises of three distinct terminals. When include in electric circuits, transistors are commonly used for switching and amplification purposes. They can change the state of the circuits from On to Off and at the same time, they can amplify the current that is getting into the circuit, from low to a higher level.
The history of transistors dates back to 1947 when three Americans; Willian Shockley, John Bardeen and Walter Brattain invented the first transistor.
The semiconductor layer of a transistor can have N-type material or P-type material. In terms of the construction and arrangement, there are three layers and either the P-type or N-type can be sandwiched. This implies that you will end up with either PNP or NPN transistor configurations.
Each of these layers is connected to terminals named base, emitter, and collector for the case of a bipolar junction transistor (BJT) transistor and source gate and drain for the case of a field effect transistor (FET).
Transistors come in different sizes and have different power specifications. Your choice will always depend on the application area as some applications will require high-spec transistors while other applications will require lower-spec transistors.
What is a vacuum tube?
A vacuum tube is an active electronic device that is directly installed on the path of a circuit. It utilizes a vacuum to control and regulate the flow of electric current. The vacuum is created by a sealed glass which prevents air and other elements from getting into it. The functionality of a vacuum tube is the reason why it is normally referred to as an older version of the transistor.
The history of the vacuum tube dates back to 1904 when it was invented by John Ambrose Fleming, an English physicist. The first vacuum tubes were mainly used as switching devices.
The vacuum tubes were similar to the cathode ray tubes that were used for the televisions. A typical vacuum tube comprises of two components; an Anode and a cathode. Both the components were enclosed in an air-tight glass meaning that all the air in the tube was removed and the glass sealed. Electrons are generated at the cathode and collected by the anode at which potential difference is applied.
Heat generation and high energy consumption were the main demerits associated with vacuum tubes.
Differences between transistors and vacuum tubes
The table below highlights the key differences between transistors and vacuum tubes.
Area of difference | Transistor | Vacuum tube |
Definition | A transistor is a semiconductor material that comprises three terminals. The working mechanism of a transistor ensures that it controls the current and also amplifies electric signals | As we have defined, a vacuum tube is an electric device that comprises of a vacuum sealed in a vacuum tubing. The device is designed to regulate current and signal |
Structural construction | Semiconductor is the main material that is used in the construction of the transistors. The semiconductor consists of electron carriers and as well as holes. The construction ends up making PNP and NPN configurations | The construction of a vacuum tube consists of anode and cathode that are positioned at the opposite ends of the tube. An air-tight glass seals the vacuum to prevent any interference to the flow of electrons |
Conduction | Electric conduction in transistors is due to the presence of electrons and holes | Electric conduction in the vacuum tubes is due to the presence of charge carriers only |
Working principle | Transistors utilize the principle of semiconductor physics to effect the flow of electrons and holes. | Vacuum tubes work on the principle of thermionic emission. This is whereby when a cathode will release electrons when subjected to the right temperatures |
Flow of charges | In transistors charges are emitted by the emitter and will flow toward the collector. The base is used as a controller | Here, the cathode releases electrons which will flow towards the anode |
Physical dimensions/size | Transistors are way smaller than vacuum tubes. This also implies that they are easily portable | Vacuum tubes are larger than transistors. The large size limits their portability |
Voltage requirement | Require low voltage to facilitate the movement of charge carriers | The tubes require high voltage which will mainly be used for the generation of heat for releasing electrons at the cathode |
Switching time | Transistors are rapid switchers. Take short time to switch | Take a relatively longer time to switch. |
Mechanical strength | The semiconductor material is dense and hardy. It offers sufficient mechanical strength | The glass tubing makes them delicate to handle as they have less mechanical strength |
Reliability | Transistors are likely to serve their purpose for many years. They have a longer lifespan than vacuum tubes | The construction of vacuum tubes exposes them to various risks. This has a negative impact on their lifespan. |
Energy efficiency | Transistors are more energy-efficient than vacuum tubes | Consume high energy and a good percentage is dissipated in the form of heat |
Vacuum tube | Have high voltage gain | Lower voltage gain than transistor |
Effect on temperature | The performance of the transistor is rarely affected by temperature changes | A slight change of temperature has a major effect on the performance of the vacuum tube |
Input impedance | Have low input impedance | Have high input impedance |
Conclusion
From the differences above, it is clear why transistors have replaced vacuum tubes. They tend to score pretty well in every aspect. All it requires is to get high-quality transistors that are designed to deliver the best results.
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