Difference between Transformer and Amplifier

In electrical and electronics engineering, transformers and amplifiers play a crucial role in several circuits. At first sight, the function of a transformer and an amplifier may seem similar, that is, increasing the level of voltage. But, a transformer can reduce the level of voltage as well, whereas an amplifier cannot.

In this article, we will discuss all the key differences between a transformer and an amplifier by considering different parameters such as basic definition, circuit components, primary function, applications, etc. But before that, let's check some of the basics of transformers and amplifiers so that it becomes easier to understand the differences between them.

What is a Transformer?

A transformer is an electrical device which can change the level of input AC voltage. It can either increase the value of voltage or reduce it depending on the circuit configuration of the transformer.

A typical transformer consists of two windings namely primary winding and secondary winding. Both these windings are wound on a common magnetic core. The AC supply is connected to the primary winding and the transformed output of the transformer is taken from the secondary winding.

The transformation in the voltage of the AC supply takes place as −

  • If the number of turns in the primary winding is greater than that are in the secondary winding. Then, the output voltage of the transformer will be less than the input voltage.

  • On the other hand, if the primary winding turns are less than the secondary winding turns, then the output voltage is more than the input voltage.

Transformers are used in both electrical and electronic circuits for voltage transformation purpose. Some common examples of circuits in which the transformers used are mobile charger, rectifier, motor circuits, power stations, distribution stations, etc.

What is an Amplifier?

An electronic circuit which accepts a weak signal as its input and produces an output signal of high magnitude or intensity is called an amplifier. Therefore, in simple terms, an amplifier is a device or circuit which can increase the level of input voltage.

An amplifier uses a source of DC power to increase the energy or intensity of the weak signal. It because an amplifier does not generate energy on its own. A simple amplifier circuit can be designed by using a BJT (bipolar junction transistor). When a bipolar junction transistor is operated in active region, it functions as an amplifier and can amplify the weak signals.

In practice, a BJT in common emitter configuration is used as an amplifier. In the CE circuit of BJT, the weak signal is fed to the circuit through base-emitter terminals. As the base region is very small so the entire current will pass through the collector and the signal of increased magnitude is obtained at load terminals by connecting a load resistor.

Amplifiers can be classified depending on the type of parameter of the signal amplified, which are voltage amplifier, current amplifier and power amplifier. The amplifiers are mainly used in electronic and power electronics circuits such as music systems, booster circuits, etc.

Difference between Transformer and Amplifier

The primary function of both transformers and amplifiers is same, i.e., changing the level of voltage. However, there are many differences between amplifiers and transformers that are given in the following table:

Basis of Difference Transformer Amplifier
Definition An electrical device which either increases or decreases the level of voltage of input AC supply is known as a transformer. An electronic circuit which increases the strength of a weak signal in terms of voltage, current or power is known as amplifier.
Construction A transformer consists of two windings namely primary and secondary wound on a common magnetic core. An amplifier consists of an amplifying component such as BJT or any other transistor, a DC power source.
Change in current and voltage A transformer changes the level of voltage and current in the same ratio, which means if it increases the voltage by a certain factor, it will reduce the current by the same factor. An amplifier can increase voltage and current individually as well as simultaneously.
Need of DC supply A transformer does not require extra direct current supply for its operation. An amplifier always need a source DC power for working.
Process of voltage amplification In case of a transformer, we need to increase the number of turns in the secondary winding for the amplification of voltage. In an amplifier, a constant DC voltage is modulated in response to an input AC voltage to obtain the amplification of output voltage.
Device type A transformer is an electromagnetic device. An amplifier is a semiconductor based electronic circuit.
Decrease in voltage A transformer can reduce the voltage of input AC supply. An amplifier cannot decrease the voltage of input supply.
Relation between source and output impedances For a transformer, the output impedance depends on the source depends. The output impedance of an amplifier can be independent of the source impedance.
Relation between input and load currents In case of a transformer, the input current is proportional to the load current. For an amplifier, the input current is almost independent of the load current.
Amplification of DC signal A transformer cannot amplify the DC voltage because it operates on the principle of electromagnetic induction, i.e. di/dt. In case of DC, there is no continuous di/dt. So it cannot amplify DC signal. An amplifier can amplify the DC signals as well.
Applications Transformers are used in different electrical and electronic applications for voltage transformation like in rectifiers, battery chargers, voltage stabilizers, power transmission and distribution, etc. Amplifiers are mainly used in electronic and power electronic circuits such as in audio signal amplification in music systems, signal boosters, etc.


The most significant difference that you should note here is that a Transformer can increase or decrease the value of voltage, whereas an Amplifier can only increase the value of voltage.

Updated on: 22-Sep-2022

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