One of the greatest inventions in the history of electrical engineering occurred in 1947 at the Bell Telephone Laboratories in New Jersey. The transistor was invented, and its inventors – William Shockley, Walter Brattain, and John Bardeen – were later awarded the Nobel Prize in Physics in 1956. The transistor created a revolution in electronics that led to the creation of ever more powerful semiconductor devices with increasing levels of efficiency and dependability. While transistors have transformed the modern world, there are both advantages and disadvantages of transistors that should be considered when using them, whether in specific applications or generally.
Advantages and Disadvantages of Transistors
Transistors are devices that act as switches or gates to control the flow of electrical voltage and current. They’re made from semiconductive materials and are essentially miniature semiconductors, each featuring at least three terminals connecting to an external circuit. Characteristically consisting of three semiconductive layers, transistors act as amplifiers or switches capable of carrying electrical currents. Transistors convert smaller input currents into larger output currents when working as amplifiers. If operating as switches, they exist in one of two distinct states – either on or off – that control the flow of electricity through electronic devices or electrical circuits.
There is only one circuit element on each transistor, and a small number of transistors can be combined to act as electronic switches within integrated circuits. These integrated circuits are made up of numerous interconnected transistors that are then baked into silicon to create different types of microprocessors. Millions of these transistors exist on the computer chips that store memory and control processes for a wide range of modern electronic devices like smartphones, gaming consoles, flash drives, and digital cameras. They convert alternating current into direct current in power supply inverters and other high-power and low-frequency applications. They also generate radio waves in oscillator circuits and other high-frequency applications.
Advantages of Transistors
Transistors’ versatility has made them an integral element of modern electronics and all computing technology. Now, let’s look at some of the advantages and disadvantages of transistors…
Some advantages of using a transistor include:
- Allows for easy testing with a multimeter.
- Can be used to regulate power delivery to the electrical load in choppers and inverters.
- Can quickly switch between the “on” state to carry large currents while conversely blocking very high voltages when in the “off” state.
- Capable of operating at switching frequencies between about 10 to 15 KHz.
- The compact size means putting tens of thousands (or more) of transistors on a circuit board to create an electrical circuit is possible.
- Decades of use have resulted in the development of many types of transistors used in countless applications.
- Exceptional capabilities for switching frequencies make them ideal switches.
- Inexpensive, quick, and soundless means for controlling high-power circuitry.
- Low operational voltage makes it safe and suitable to fit into tight spaces.
- Requires minimal supply of voltage while providing high voltage gain.
- Serves a wide variety of power applications, from just a handful to several hundred kilowatts.
- Significantly longer lifespans than vacuum tubes, which they replaced, with some devices with transistors still operational after 30 years.
- Simple and durable design with no moving parts allows them to withstand vibrations, minor collisions, and other wear-and-tear types while requiring very little maintenance.
- Unlike older, tube-based radios and televisions, transistors in these applications require no cathode heater.
- Very low drops in voltage, or output impedance, when in the “on” state.
- Its very small size makes it perfect for various applications, including analog and digital circuits, cell phones, computers, microprocessors, power regulators, radar, and radios.
- Works well in cold temperatures, so doesn’t require a heating element, while output voltage remains constant when temperatures rise or fall.
Essentially transistors do the same thing as two P-N diode junctions that are stacked next to each other but in opposite directions. Created via a method known as “doping,” a transistor’s P-N junction marks the boundary between two different semiconducting materials within a semiconductor. Transistors are considered either NPN or PNP, with PNP transistors having a lower current-to-voltage rating than NPN transistors, which tend to be more desirable for power conversion applications. PNP transistors switch on with a low signal. In contrast, NPN transistors switch on via a high signal, with the P representing positive polarity in the emitter terminal and N representing the negatively charged coating at the base terminal.
Transistors are also primarily made from silicon, a common element that resists the conduction of electrical current. Silicon allows transistors to operate at higher junction temperatures and currents, making them useful for alternating current applications, which require ranges up to several hundred kilowatts.
Disadvantages of Transistors
While transistors offer many advantages, the disadvantages of transistors should be contemplated when considering their use in an application.
Some disadvantages of using transistors include:
- As they produce very little energy, semiconductor fuses cannot protect transistors.
- The current capacity in reverse blocking mode is very low.
- DC output voltage isn’t adjustable, so their output voltage can’t easily be changed.
- Difficult to identify and repair faulty capacitors due to their small size.
- Don’t operate well over a switching frequency of about 15 kHz.
- Low input impedance except for the field-effect transistors often used for digital integrated circuits.
- Must be protected against high voltages and currents, which can damage transistors.
- Sensitive to radiation and voltage stress while also being prone to secondary breakdowns due to thermal runaway.
- Techniques for manufacturing capacitors require automation and “clean room” environments, along with stringent quality control.
- Very strong electrical currents can cause transistors to heat up and break down.
- The higher the frequency when switching, the greater the loss of power.
- When switched “on,” there is always voltage crossing the transistor. When switched “off,” there’s always a slight leakage of current.
- Comparatively slow switching time compared to the high alternating frequency of current and voltage.
Most transistor failures occur due to excess dissipation, either directly or indirectly, or because applied voltages exceed a transistor’s maximum design limitations. For example, most transistors cannot block reverse voltages over 20 V, which can easily damage the device and transistors. For this reason, transistors shouldn’t be used for control applications when working with alternating current unless utilizing a reverse shunting diode to connect between the collector and emitter. Despite these difficulties when using transistors in certain applications, they’ve proved invaluable and have had an outsized impact on advancing modern electronics and electrical technology.
To learn more about the advantages and disadvantages of transistors and other electronic components we carry, contact the experts at Solid State Inc. If you already know what you need, we welcome you to request a quote.