Transistors as Amplifiers

Before introducing transistors as amplifiers, we need to understand transistors. Transistors are 3 terminal devices which are semiconductors. The following terminals are Emitter as E, base as B and collector as C.  The transistors can act in three different regions like cutoff region, saturation region and the active region. 

In this article, we will discuss the third region i.e., the active region where transistors work as an amplifier. Transistors as amplifiers are mainly involved in radio, optical communication fibre, audio, etc. We will also define the characteristics, uses of amplifiers and how to calculate the gain in amplifiers.

Let’s start by defining a transistor as an amplifier.

 Transistor as an Amplifiers

An Amplifier circuit can be described as a circuit that can be used to amplify a signal. In the amplifier, the input is a voltage or current and output is an input signal for the amplifier. A transistor as an amplifier can be classified into three categories which are Common base or CB, Common Emitter or CE and Common Collector or CC. Transistors as Amplifiers in common emitter configuration are used in applications like audio amplifiers. 

Secondly, the amplifiers are classified based on the input applied and the output collected such as class A, class B,  class C and class D, etc. 

Lastly, the amplifiers are designed based on its main factor called efficiency and to achieve efficiency they can be designed in the form of different stages; they are single-stage, multi-stage, etc. 

 Characteristics of Transistors as an amplifier (common emitter configuration)

 There are various characteristics that can be seen in transistors as an amplifier(common emitter configuration). The following characteristics are given in the table below. 

From the above-mentioned characteristics of the common-emitter configuration, it can be seen that it provides a high level of voltage gain which is the main attribute in electronic circuit design required in applications. 

The gain in common emitter configuration

 To calculate Voltage Gain in common emitter configuration

 Voltage Gain or Av = VCEVBE 

= Change in Output current effective loadChange in input current input resistance

= Ic RacIb Ri

= Rac Ri

Where, 

Av is Voltage gain

is current gain

 To calculate Current Gain in common emitter configuration

=  Ic Ib

Where, 

 Ic = change in collector current

Ib = change in base current

= current gain

 To calculate Power Gain in common emitter configuration,

AP = (Ic)2 Rac (Ib)2 Ri

Or in other words 

Power gain = Voltage Gain  Current Gain 

 Advantages and Uses of Transistor as an Amplifier

Transistor as an amplifier has various advantages and uses in the field of electronics and communication. They are as follows:

1. Transistors as amplifiers can be used in long-distance communication due to the high intensity of the signal obtained at the output.

2. Transistors as amplifiers can be used in radio signals amplification.

3. Transistors as amplifiers can be used in wireless communication.

4. Transistors as amplifiers can be utilised in the signal broadcasting of FM.

5. It can be used in the communication of optical fibre.

 Conclusion

Transistors as an amplifier can be described as a generally used circuit in our day to day life to amplify sounds. These circuits are widely used in radio and audio devices. The design of a circuit may vary depending on the requirement. In the above article, we must have solved the questions regarding the transistor as an amplifier and other related topics.