Voltage Amplifier : Circuit, Voltage Gain, Vs PowerAmplifier & Its Applications

An amplifier is an electronic device used to increase the current, voltage (or) power of a signal and it improves the signal’s strength without changing the signal shape. Different kinds of Amplifiers are used in wireless communications, broadcasting, and all kinds of audio equipment. There are different forms of amplifiers which range from Op-Amps and small signal amplifiers to large signal & power amplifiers. Amplifiers are classified into two methods based on function; voltage amplifiers (or) power amplifiers. The amplifier classification mainly depends on the signal size, its physical configuration & how it processes the input signal which is the main relationship between the input signal & the current supply within the load. This article provides brief information on a voltage amplifier, their working, and their applications.

What is a Voltage Amplifier?

A type of amplifier that creates a higher output voltage as compared to the input voltage is known as a voltage amplifier. This amplifier is used whenever the higher voltage transmission across a longer wire is necessary. This amplifier improves the power of an electrical signal without changing its character significantly. These are significant in electronics to improve clearer audio signals, sharper images, & more accurate sensor readings.

This amplifier does not supply power, however, increases the sum of power coming throughout a given circuit to get the desired result. Generally, these amplifiers are not suitable to power different devices like motors although increase the sum of available voltage to help in reading signals from different controls.

Voltage Amplifier
Voltage Amplifier

Voltage Gain

An amplification unit designed mainly to enhance the voltage level of the input signal applied to an amplifier is called a voltage amplifier. This amplifier’s design mainly depends on obtaining the maximum achievable voltage gain. So, the gain of this amplifier is the ratio of the output value to the input value. This is the ratio equivalent to the o/p voltage to the i/p voltage. The voltage amplifier formula for voltage gain is given as;

Av = Vout/Vin

These amplifiers draw extremely small amounts of power from the connected load. These types of amplifiers are known as small-signal amplifiers because the signal magnitude that is provided as input is extremely small and is raised through the amplifier circuit.


Voltage Amplifier Circuit

Designing this amplifier circuit is quite simple because it needs basic electronic components. These are also called voltage difference amplifiers which amplify the difference within voltages in an electronic circuit. Thus, this changing output voltage can be read & analyzed.

Voltage Amplifier Circuit
Voltage Amplifier Circuit

The voltage amplifier circuit is shown above which amplifies an input voltage signal & provides an o/p voltage signal. This amplifier is a voltage-controlled voltage source. The input impedance of this amplifier must be high & the output impedance must be low. From the below circuit, we can find that if the Rin is >> Rs then Vin is ≈ Vs If ‘RL’ load resistance RL is >> Rout, then;

Vout ≈ AvVin

Voltage gain Av = Vout/Vin = Vout/Vs

An ideal amplifier must include infinite input resistance & zero output resistance. This amplifier gives an output voltage that is proportional to the input voltage. The proportionality constant is independent of the source magnitudes & load resistances.

Difference between Voltage Amplifier and Power Amplifier

Both the voltage and power amplifiers are used to enhance the power of an input signal. So, a voltage amplifier focuses on voltage amplification exclusive of important power gain whereas a power amplifier provides large power gain for driving high-power loads. Both these amplifiers are used in audio & RF applications. The differences between these two amplifiers are discussed below.

Voltage Amplifier Power Amplifier
An amplifier that is designed to amplify an input signal’s voltage is known as a voltage amplifier. An amplifier that is designed to provide a considerable quantity of power gain for the input signal is known as a power amplifier.
This amplifier enhances input signals the amplitude without providing considerable power gain. This amplifier uses a low-power electrical signal & enhances its power level to make it appropriate for driving high-power loads or loudspeakers.
It is also called a small signal amplifier because it has a small magnitude input signal. The power amplifier is known as a large signal amplifier because that needs a large magnitude input signal.
In this amplifier circuit, the transistor base is thin because it is not designed to handle the huge current. The transistor base in this amplifier circuit is fairly thicker which handles large currents.
The transistor used in this amplifier is a low (or) medium power transistor which has a small physical size The transistor used in this amplifier is a high-power transistor which has a large physical size
The collector current value in this amplifier is quite low that is 1 mA. The collector current value in this amplifier is high, around 100 mA.
The amount of AC o/p power given by this amplifier is low. The amount of AC o/’p power given by this amplifier is high
The current gain of this amplifier is low. The current gain of this amplifier is high.
It is coupled with RC. The current amplifier is coupled with the transformer.
Heat dissipation is low. Heat dissipation is high.
These amplifiers are used frequently in audio equipment to amplify the signal without increasing its power significantly. Power amplifiers are used commonly in wireless communication systems, audio systems, and various scientific & industrial applications wherever high output power is necessary.

Difference between Current Amplifier vs. voltage Amplifier

Both the current amplifier & a voltage amplifier are electronic devices mainly used for amplifying electrical signals, however, they work based on different principles. The difference between these two amplifiers is discussed below.

Current Amplifier

Voltage Amplifier

An amplifier that is used to enhance the input signal’s current by maintaining stable voltage is known as a current amplifier. An amplifier that is used to enhance the input signal’s voltage by maintaining a stable current is known as a voltage amplifier.
This amplifier allows a little input current to control a larger output current. This amplifier allows a little input voltage to control a larger output voltage.
The input and output of this amplifier are current with low input impedance and high output impedance. The input and output of this amplifier is voltage with high input impedance & low output impedance.
It is used for voltage amplification. The current amplifier is used for current amplification.
This amplifier has extremely high voltage gain, input impedance & less output current. This amplifier has low voltage gain, large current gain, and medium range to high i/p impedance.


The applications of voltage amplifiers include the following.

  • This is used to enhance the amplitude of the o/p voltage of the signal.
  • These are most frequently used in electronic devices.
  • It is used in a variety of applications like; wireless communication, signal broadcasting, and audio equipment such as speakers.
  • It is used in applications wherever we require signal transmission at maximum voltage throughout a long wire.
  • These amplifiers are used in speakers for amplifying audio signals as well as in radios for amplifying weak radio signals received by an antenna.
  • It can be used as an impedance impedance-matching circuit and switching circuit.

Thus, this is an overview of voltage amplifiers, circuits, working, differences and their applications. This gives an o/p signal with an increased level of voltage whenever the input of this is a low voltage signal. This amplifier is used where we require signal transmission at maximum voltage throughout a long wire. Here is a question for you, what is an amplifier?