18 Transistor Examples in Daily Life

TransistorA transistor is a three-terminal electronic component made up of semiconductor material that is basically used to control the flow of current through an electronic circuit. The ability of transistors to control the flow of current through a circuit makes them fit for applications where switching, clipping of signals, amplification, or regulation of voltage is usually desired. Transistors can be broadly classified into three categories, namely, bipolar junction transistors or BJTs, field-effect transistors or FETs, and insulated-gate bipolar junction transistors or IGBJTs. Some of the prominent advantages of transistors include compact size, less cost, low mechanical sensitivity, long life span, and high efficiency. Also, transistors do not operate on very high voltages, which is why they have significantly low power consumption and a faster switching rate. Transistors also have certain disadvantages such as they have limited electron mobility and can not handle any type of interference introduced by cosmic radiations. This may lead the devices to break down easily in case of electrical and thermal events.

Examples of Transistors in Daily Life

There are a number of daily life applications that make use of transistors to control and execute their basic operations. Some of them are listed below:

1. Amplifier Circuits

Amplification is the process by virtue of which the strength of a weak signal can be raised to a certain level. Most amplifier circuits make use of transistors as their prime component to increase the strength of the input signal while maintaining the integrity of the information or the data possessed by it at the same time. A transistor is an electronic device that commonly functions as an amplifier when a DC bias voltage is applied across its emitter-base junction. The DC bias voltage tends to maintain the forward bias condition of the transistor irrespective of the negative or the positive polarity of the input signal. Due to the high input and low output resistance of the circuit, the emitter current and the collector current tend to flow through the load resistor and lead to a large magnitude voltage drop across the load resistor. This means even a small variation in the input signal causes a significantly large change in the output signal, thereby amplifying the input signal. The amplification property of transistors can be utilized in research labs, sound systems, signal analysis and reconstruction, and various other related applications.

Amplifier Circuits

2. Microphones

Microphones are a classic example of daily use devices that make use of transistors for their basic operation. Various microphones such as a condenser microphone typically make use of an electronic circuit that tends to perform impedance modification by converting mechanical waves into an electrical signal. For this purpose, usually, field-effect transistors are embedded in the internal circuitry of the microphones. The capsule of a condenser microphone generally acts as a transducer that picks up sound waves as an input signal, pass it through the processor and produces an output signal that is electrically amplified and processed audio signal. High impedance is one main characteristic of the output audio signal communicated by the condenser capsule that causes a significantly low amount of current to flow through the circuit. To balance this, FETs or field-effect transistors are connected on the output side of the microphones. The gates of a field-effect transistor have an extremely high impedance value, while the impedance at the drain of field-effect transistors is comparatively low. This is the reason why the current flowing in the circuit tends to pass through the drain of the transistor. The high impedance signal from the condenser microphone capsule that reaches the input terminal of the FET suffers a significant reduction in the impedance value and is used to modulate the low impedance signal at its output. Finally, the signal output from the field-effect transistor is fed to the output circuit of the microphone. The signal passes through the mic cable to a microphone preamplifier and produces an amplified output sound signal.


3. Oscillator Circuits

The main purpose of oscillatory circuits is to produce continuous, periodic, and undamped output signals. In other words, an oscillator circuit basically converts the unidirectional current flow from a direct current source into an alternating signal. The frequency of the alternating signal generated by the oscillator typically depends on the value of the electronic components embedded in the circuit. A transistor can be designed to produce continuous undamped oscillations of a particular frequency by properly connecting it to a tank and feedback circuit, hence oscillator circuits are yet another example of applications that make use of transistors.

File:Phaseshift across resonance (forced harmonic oscillator).gif - Wikimedia Commons

4. Electronic Switch

One of the most prominent applications of transistors is switching. A transistor basically has four regions of operation, i.e., namely active, saturation, cut off, and forward active. For a transistor to act like a switch, the saturation and cut off region of operations of a transistor are generally used. This is because when the transistor is operated in the saturated region, the current value is maximum and the voltage level is equal to zero. Similarly, when the transistor is operated in the cut-off region, the value of current is zero and the value of voltage is maximum. The operation of a transistor in the saturation and cut off region resembles the working of a closed and open switch respectively. A transistor operating as a switch tends to produce no noise and the rate of the switching operation provided by the transistor is quite high. Also, transistor switches do not have mechanical parts, hence there exist fewer chances of device failure due to wear and tear. Other advantages of using transistors as switches include compact size, lightweight, low cost of manufacturing, minimum maintenance cost, etc.

Electronic Switch

5. Compact Disc Players

A compact disc typically contains multiple lands and pits. The light emitted by the light source embedded in the internal circuitry of compact disc players is directed towards the surface of the compact disk. The light gets reflected back at certain angles on hitting the lands and pits of the disk. The phototransistor embedded in the circuitry mainly functions to collect and sense the reflected light and converts it into the form of an electrical signal. Compact disc players generally prefer phototransistors over photodiodes for their basic operation. This is because phototransistors provide numerous advantages such as more sensitivity toward the light signal, the capability of operating on voltage as well as current, faster response rate, less reactivity, and a higher immunity towards interference or noise signals. Also, a phototransistor allows the flow of a higher magnitude current through the circuit as compared to the photodiode.

Compact Disc Players

6. Transistor LASERS

Transistor laser was first demonstrated in 1947 by John Bardeen, an American engineer and Walter H. Brattain, an American physicist. A transistor laser is basically a coherent source of light that offers a highly focused, unicolour, and directional light that can be used for long as well as short-distance communication. A transistor laser is also known as a light-emitting transistor. Transistor laser communication offers a significantly high data transmission rate, high security, and fewer chances of data loss. Also, transistor lasers are much faster as compared to diode lasers.

Transistor LASERS

7. Night Vision Enhancer

Night vision is the technology that helps a person visualise the surroundings in a totally dark environment and tends to uplift the visual experience in a region that has dim or low-intensity light. The application of night vision technology can be easily observed in defence operations, security and surveillance, crime scene investigation, mining, etc. Two main technologies used to enable night vision are called thermal imaging and regular vision. The working of night vision enhancer devices using either thermal imaging or traditional vision involve the transmission of infrared radiations into the surroundings, collecting the light radiations that get reflected after striking the surface of the objects present in the surroundings with the help of a detector circuit, and passing on the signal to transistors. The transistors tend to amplify the received light radiations and help improve visibility. The traditional or regular vision technology is not able to function properly in complete darkness, hence thermal night vision-enhancing devices are preferred over regular vision-enhancing devices in a majority of cases.

Night Vision Enhancer

8. Hearing Aid  

A hearing aid is yet another daily life gadget that demonstrates the use of transistors in real life. The microphone embedded inside a hearing aid device primarily takes the audio signals from the surroundings and converts them into the form of an electric signal. This electric signal is further coupled to a transistor that helps amplify, smoothen, and filter the original signal, thereby enhancing the audio characteristics of the input signal. Using transistors in hearing aid devices is advantageous as they are compact, lightweight, and operate on low current and voltage values.

Hearing Aid  

9. Smoke Detectors

One can easily make a smoke detector device by deploying electronic components, namely, a smoke sensor, resistor, potentiometer, power supply, transistor, light emission diode, and buzzer on a printed circuit board or a breadboard as per the circuit diagram of a smoke detector circuit. The tools required to make the circuit include soldering iron, soldering wire, wire clipper, and jumper wires. Each electronic component used in the circuit has its own use and significance. For instance, the light-emitting diode and the buzzer are connected on the output side of the circuit and are used to indicate the presence of smoke in the environment, thereby indicating fire. The smoke sensor is connected to the input side of the circuit to monitor and observe the temperature and humidity values of the surroundings and transform the input signal into an analogue or digital electrical signal for further processing. The potentiometer serves the purpose of calibrating the circuit. Likewise, the transistor is used in a smoke detector circuit to set a threshold level and to control or manipulate the working of the circuit as per the user’s requirement. Generally, in smoke detection circuits, NPN type transistors are preferred as the majority charge carriers of an NPN transistor are electrons and electrons have better mobility than holes. The minimum value of voltage required by transistors to get activated is approximately equal to 0.7 volts. The working of a smoke detector system is quite simple. It makes use of a voltage divider circuit that is applied to the base of the transistor. When the smoke sensor detects the presence of smoke in the environment, a significant reduction in its internal resistance is observed. This reduction in the value of resistance causes a voltage drop. As a result, the voltage value at the base of the transistor increases. When the voltage value crosses the 0.7 volts mark, the transistor gets activated and turns on the light-emitting diode and buzzer.

Smoke Detectors

10. Infrared Receivers or Invisible Light Receivers

An infrared receiver or infrared sensor is an electronic device that takes the infrared radiations emitted by the objects present in the surroundings as input, manipulates and analyses the signal by passing it through the processing unit, and generates an output signal corresponding to the input. The output is then presented on an output device generally in the form of pictures, heat maps, or statistical data. The electronic components typically required for the construction of an infrared sensor include light-emitting diodes, infrared light-emitting diodes, resistors, connecting wires, and transistors. The first step of making an infrared sensor is to place and embed the electronic components on a printed circuit board as per the circuit diagram. The next step is to solder the components in place to lock their positions as per the circuit diagram. The final step involves completing the circuit by making tracks on the printed circuit board with the help of solder or by connecting the components with the help of jumper wires. Transistors of both NPN and PNP types are used in the infrared sensor circuitry. The collector terminal of the NPN transistor is required to be connected to the base terminal of the PNP transistor. An infrared light-emitting diode is connected to the base of the NPN transistor via a resistor, while another infrared light-emitting diode is connected between the anode terminal of the previous infrared light-emitting diode and the emitter terminal of the NPN transistor. To display the output, a light-emitting diode is attached to the collector terminal of the PNP transistor through a resistor. When the infrared light radiations emitted by the infrared light-emitting diode strike the surface of the objects present in the surroundings, a part of the radiations bounces back. The reflected light causes a small magnitude current to flow through the infrared light-emitting diode detector. When the value or magnitude of current rises above 0.7 volts, the transistors get activated and the output LED glows. The use of a transistor in an infrared sensor circuit makes it more economical, compact, and lightweight than the other infrared sensors. Also, the sensitivity level of the transistor-based infrared sensors is significantly high. Infrared receivers are also known as invisible light receivers as the light radiations emitted by the infrared light-emitting diodes are not visible to humans with naked eyes. Some of the prominent applications that make use of infrared sensors include infrared thermometers, infrared heaters, infrared cooking equipment, infrared camera, and infrared lamps.

Infrared Receivers or Invisible Light Receivers

11. Automatic Night Lamp

Transistors are often used in constructing automatic night lamps. Such lamps can be used in place of traditional street lights to automize them and save energy. The electronic components and devices required for the construction of a transistor-based automatic night lamp include a transistor, carbon resistor, light-dependent resistance, light-emitting diode, power supply, connecting wires, and printed circuit board. The first step of construction is to lay out the electronic components on the printed circuit board and make circuit tracks as per the circuit diagram. The second step is to fix the components in place by soldering them. The final step is to clip off the extra pins or terminals and provide insulation to the circuit so as to avoid any current leakage or short circuit. The operation of the transistor-based automatic night lamp is primarily based on the working of a light-dependent resistance. The flow of current through a light-dependent resistance or LDR depends on the intensity of the light present in the surroundings. This means that if the light-dependent resistance is placed in darkness, the value of the resistance tends to increase and the device prohibits any flow of current. Similarly, when the light is made to strike the surface of the light-dependent resistor, the resistance value decreases and the component begins to act as a conductor. The transistor here is used to control the performance of the circuit and is used to communicate the signal from the light-dependent resistance to the light-emitting diode, thereby allowing the light-emitting diode to glow when the circuit is placed in the dark and get turned off when light is present in the surroundings.

Automatic Night Lamp

12. Computer Processors

Transistors are known to be the basic building units of microprocessors and microcontrollers. The processing units used in computers are basically an assembly of multiple transistors interconnected to each other in cascaded or parallel form. The switching and other related operations of transistors help a person operate the computer and gain access to web surfing, data storage, playing games, computing, analysis, and various other functionalities.

Computer Processors

13. Air Conditioner

Air conditioners tend to form yet another example of the daily use gadgets that makes use of transistors. The sensors used by the air conditioners to compare the room temperature with the desired temperature consists of an assembly of transistors that act as comparators. Here, the task of sending and receiving signals back and forth between the device’s internal circuitry and the external environment is controlled and manipulated by transistors. Whenever a difference in the current temperature and the desired temperature is observed, a signal is sent to the compressor to vary the temperature accordingly. Similarly, in case the current temperature value exactly matches the desired temperature value, a signal to maintain the temperature constant is circulated.

Air Conditioner

14. Graphics Processing Unit

GPU or graphic processing unit is an integral part of the devices where high definition graphics rendering is primarily desired. GPUs contain an assembly of billions of transistors arranged in a cascaded or parallel form. Almost all the operations carried out by a graphic processing unit rely on transistors.

Graphics Processing Unit

15. Integrated Circuits

Integrated circuits are a classic example of devices that make use of transistors in real life. On the basis of the number of transistors used in construction and fabrication, integrated circuits can be broadly classified into five subcategories, namely, small-scale integrated circuits, medium-scale integrated circuits, large-scale integrated circuits, very large scale integrated circuits, and ultra large scale integrated circuits. The range of the number of transistors used by small-scale integrated circuits, medium-scale integrated circuits, large-scale integrated circuits, very large scale integrated circuits, and ultra large scale integrated circuits is typically equivalent to 10 to 100, 100 to 1,000, 1,000 to 20,000, 20,000 to 10,00,000, and 10,00,000 to 1,00,00,000. respectively. Integrated circuits are an integral part of analogue as well as digital electronic gadgets and devices such as logic gates, op-amps, voltage regulators, timers, comparators, flip flops, registers, etc.

Integrated Circuits

16. Video Game Cartridges

Video game cartridges or video game cassettes tend to form yet another example of applications that make use of transistors to execute their basic operations such as graphics rendering, input and output controls, audio output, amplification of the digital and analogue signal, termination of active operations, etc. The internal circuitry of such game chips typically contains a processing unit, memory unit, graphics unit, arithmetic and logical unit, input pins, output pins, and one or more expansion slots. The basic building blocks of a majority portion of such game cartridges are transistors.

Video Game Cartridges

17. Laser Range Finder

A laser range finder is a device or a gadget that is generally used to measure the distance between the target object and the instrument. Architecture, interior decoration, construction, hunting, agriculture, defence, sports, etc. tend to form some of the daily life applications where laser range finder devices can be employed. The internal circuitry of the laser range finder device primarily contains transistors to perform the switching, amplification, and other related operations. Also, the motor control operation or the motor drivers of the internal circuit of a laser range finder device usually contain an assembly of pulse width modulators and transistors. A laser range finder is also known as a laser telemeter.

Laser Range Finder

18. Astronomy

Astronomy is the science that deals with the study of celestial bodies and objects located in space. Due to the huge distance between the observer and the target object and the lack of lightning in outer space, obtaining images and information about celestial objects is a difficult task. To resolve this problem, a number of astronomical gadgets and devices make use of complex electronic circuits. In such circuits, transistors tend to play a prominent role and help improve the clarity of the images obtained by functioning as a switch as well as a signal amplifier.


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