To use a transistor as an amplifier
Show Hint
Transistors are essential components in electronic circuits used for amplification.
- the emitter base junction is forward biased and the base collector junction is reversed biased
- no bias voltage is required
- both junction are forward biased
- both junction are reverse biased.
The Correct Option is A
Approach Solution - 1
To use a transistor as an amplifier the emitter-base junction is forward biased while the collector-base junction is reverse biased.
Read More From Chapter: Semiconductor Electronics
Approach Solution -2
The Correct Answer is (A)
Real Life Applications
Real-life applications of using a transistor as an amplifier include:
1. Transistors amplify weak audio signals from devices like microphones and music players, enabling us to enjoy clear and loud sound through speakers.
2. They boost weak radio signals, allowing us to receive a wide range of radio stations with improved signal quality.
3. They amplify TV signals to enhance picture quality and sound, delivering a better viewing experience.
4. Transistors amplify signals in mobile phones, ensuring clear voice calls and efficient data transmission.
5. They amplify signals from medical sensors, enabling accurate and sensitive measurements in various medical devices.
Question can also be asked as
1. How do you bias a transistor for amplification?
2. What is the difference between forward bias and reverse bias?
3. What are the two biasing conditions for a transistor to work as an amplifier?
Approach Solution -3
The Correct Answer is (A)
Transistors are essential components in electronic circuits used for amplification. To utilize a transistor as an amplifier, specific biasing conditions need to be established.
- A transistor is a semiconductor device that can amplify or switch electronic signals.
- It consists of three layers: the emitter, base, and collector, forming two junctions - the emitter-base (EB) and base-collector (BC) junctions.
Amplifier Operation
- An amplifier is a circuit that increases the amplitude or power of an input signal without significantly distorting its waveform.
- To use a transistor as an amplifier, it needs to be biased properly, ensuring it operates within its active region.
Forward Biasing the Emitter-Base Junction
- Biasing the emitter-base junction involves applying a voltage in a way that allows current to flow in the desired direction.
- To use a transistor as an amplifier, the emitter-base junction is forward-biased by applying a positive voltage to the base terminal relative to the emitter terminal.
- Forward biasing enables the flow of majority carriers (electrons in an NPN transistor) from the emitter to the base, allowing for signal amplification.
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Reversed Biasing the Base-Collector Junction
- Biasing the base-collector junction involves applying a voltage in a way that blocks the flow of current.
- In an amplifier configuration, the base-collector junction is reversed biased by applying a negative voltage to the collector terminal relative to the base terminal.
- Reversed biasing prevents the flow of majority carriers (electrons in an NPN transistor) from the base to the collector, allowing the amplified signal to be efficiently extracted at the collector terminal.
Amplification Process
- The forward-biased emitter-base junction provides the input signal, allowing a small current to control the larger current flowing through the transistor.
- The transistor's gain or amplification is determined by the ratio of the output current (collector current) to the input current (base current).
- Proper biasing of the emitter-base and base-collector junctions ensures the transistor operates within its linear range for effective amplification.
Utilizing a transistor as an amplifier involves biasing the emitter-base junction in a forward-biased configuration while reversing the bias on the base-collector junction. This biasing arrangement allows the transistor to amplify input signals accurately and efficiently.
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Top Questions on Transistors
- The typical biasing of a silicon transistor is shown in the figure.
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Concepts Used:
Transistors
Transistor
A transistor is a type of semiconductor device that can be used to both conduct and insulate electric current or voltage. A transistor basically acts as a switch and an amplifier. In simple words, we can say that a transistor is a miniature device that is used to control or regulate the flow of electronic signals.
Parts of a Transistor:
A transistor is a combination of three terminals made of semiconducting materials that help in making a connection to an external circuit and allow current to flow. The three terminals are:
- Base: The base activates the transistor. It is thin and lightly doped. It is put in the centre of the transistor.
- Emitter: The emitter is the negative terminal of the transistor. It is heavily doped and is moderately sized.
- Collector: The collector is the negative terminal of the transistor. It is located on the right side of a transistor and is moderately doped. It is larger than the emitter.
Read More: Difference Between NPN and PNP Transistor
Types of Transistors:
A transistor is a type of electronic device which is formed by p-type and n-type semiconductors.
NPN Transistor
- NPN transistor is a type of Bipolar Junction Transistor.
- In this, electrons are major current carriers, and minor ones are holes.
- Their arrangement is in such a way that N-type doped semiconductors are separated by the layer of P-type doped semiconductors which is a thin layer of material embedded between them.
- Emitter Current = Collector Current + Base Current
PNP Transistor
- PNP transistor is also a type of Bipolar Junction Transistor.
- In these, holes are the major source that carries current, and electrons are minor.
- Their arrangement is in a way that P-type doped semiconductor is separated by N-type doped semiconductor material which is a thin layer.
- Emitter Current = Collector Current + Base Current
Read More: Characteristics of a Transistor
Configurations of a Transistor:
Using the three types of configuration can be used to design any transistor circuit. The three types of configuration of a transistor are:
- Common Emitter Transistor
- Common Base Transistor
- Common Collector Transistor
Common Emitter (CE) Configuration of a Transistor
In Common Emitter Configuration, the transistor’s emitter terminal will be connected common between the output terminal and the input terminal.
Input Characteristics
- Variation of emitter current (IB) with Base-Emitter voltage (VBE) when Collector-Emitter voltage (VCE) is held constant.
- Rin = ΔVBE/ΔIB | VCE = Constant
Output Characteristics
- Variation of collector current (IC) with Collector-Emitter voltage (VCE) when the base current (IB) is held constant.
- Rout = ΔVCE/ΔIC | IB = Constant
Current Transfer Characteristics
- The variation of the collector current (IC) with the base current (IB) when the collector-emitter voltage (VCE) is constant.
- α = ΔIC/ΔIB | VCB = Constant
Common Base (CB) Configuration of a Transistor
In Common Base Configuration, the transistor’s base terminal will be connected common between the output terminal and the input terminal.
Input Characteristics
- Variation of emitter current (IE) with Base-Emitter voltage (VBE) when the Collector Base voltage (VCB) is held constant.
- Rin = ΔVBE/ΔIE | VCB = Constant
Output Characteristics
- Variation of collector current (IC) with Collector-Base voltage (VCB) when the emitter current (IE) is held constant.
- Rout = ΔVCB/ΔIB | IE = Constant
Current Transfer Characteristics
- The variation of the collector current (IC) with the emitter current (IE) when the Collector Base voltage (VCB) is constant.
- α = ΔIC/ΔIE | VCB = Constant
Common Collector Configuration of a Transistor
In Common Collector Configuration, the transistor’s collector terminal will be connected common between the output terminal and the input terminal.
Input Characteristics
- Variation of emitter current (IB) with Collector-Base voltage (VCB) when the Collector Base voltage (VCB) is held constant.
Output Characteristics
- Variation of emitter current (IE) with Collector-Emitter voltage (VCE) when the base current (IB) is held constant.
Current Transfer Characteristics
- The variation of the collector current (IE) with the base current (IB) when the Collector-Emitter voltage (VCE) is constant.