What is Voltage Follower : Working & Its Applications

Operational amplifiers are frequently used in a voltage follower design. But, this is not the finest arrangement in terms of potential risk & capacitive loading of oscillations. These loads have a huge impact on the op-amp stability based applications. Numerous compensation techniques are present to stabilize a normal op-amp. So, this application will describe the most frequent ones, used in most of the cases. This article discusses an overview of voltage follower.

What is a Voltage Follower?

Voltage follower can be defined as when the output of the op-amp circuit follows the input of the op-amp directly. So both the input and output voltages are the same. This circuit doesn’t supply any amplification. As a result, voltage gain is equivalent to 1. It is also known as unity gain, buffer & isolation amplifier. This circuit has high input impedance so it is used in different circuits. The voltage follower uses the input signal to give efficient isolation of output. The basic diagram is shown below.


Voltage Follower Circuit
Voltage Follower Circuit

What is the Purpose of a Voltage Follower?

The main purpose of voltage follower is, it gives the same input voltage as an output voltage. In other words, it has current gain but no voltage gain.

For a better understanding of this concept, the following voltage follower circuit is explained below. Consider the circuit below including a power source and less impedance load. This circuit draws a huge amount of current through the connected load because of the low resistance load. So, the circuit uses a huge amount of power from the source of power and gives high troubles within the source of power.

After that, we can believe that we are providing equal power for the voltage follower. Because, the input impedance of this circuit is high, and less amount of current will be drawn from the above circuit. This circuit output is the same as its input because of the lack of feedback resistors.

Voltage Follower in Voltage Divider Circuits

The voltage in each and every circuit can be shared with the resistance otherwise impedance of the allied components within the circuit. Once the operational amplifier is connected, then the main element of voltage will fall across it because of a huge impedance. As a result, if we utilize voltage follower within the circuit of the voltage divider circuit then it allows sufficient voltage across the given load.

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Let us discuss the voltage divider circuit as shown in the following circuit.

Voltage Follower in Voltage Divider
Voltage Follower in Voltage Divider

In the following circuit, the voltage divider is placed in the center of two resistors and the operational amplifier. The resistors used in the circuit are 10 KΩ-2. The input resistance provided by the operational amplifier will be 100 megaohms. So the equal parallel resistance can be 10 KΩ || 100 KΩ. So equivalent parallel resistance can be calculated as

= 10 X 100/ 10 + 100 => 10 kilo ohm approximately.

In the voltage divider circuit, it includes two same resistances which will give half of the voltage within the source of power. It can be provided through using the formula of voltage divider as given below,

Vout = Vin X R2/R1+R2

10X10/10 + 10 = 5Volts

Therefore, the above voltage will drops across the resistance of 10KΩ in the top as well as voltage drop across the 10KΩ resistance within the bottom & the load 100Ω resistance. So, we know that the operational amplifier functions as a buffer to get the required voltage from the load. The above circuit excluding voltage follower will not work properly because of the lack of voltage supply across the load.

Mostly, the implementation of this can be done mainly for two reasons such as isolating and buffering the output voltage purposes from the circuit to obtain the preferred voltage toward the connected load.

Voltage Follower Stability

Generally, these are used to generate an output signal that is equivalent to the input signal. But a serious problem can occur in a circuit namely stability

Oscillation within a negative feedback amplifier can be connected to phase shift to change the feedback from negative to positive.

In most of the cases, oscillation can be stopped to select an operational amplifier as unity-gain stable. Internally, these operational amplifiers are compensated to make a frequency response for stable operation whenever the device is utilized in the configuration of voltage-follower.

Advantages

The advantages of voltage follower include the following.

  • It gives a gain of power as well as current
  • Less output impedance of the circuit uses the output
  • This operational amplifier uses zero current from the i/p.
  • It avoids loading effects.
  • It does not enhance or diminish the input signal’s amplitude
  • High-frequency noise cannot be filtered out.
  • It has less output impedance
  • It has a high input impedance
  • Unity transmission gain

Applications

The applications of voltage follower include the following.

  • These are used in S & H circuits
  • Buffers used in logic circuits.
  • Used in active filter
  • It is used through a transducer in bridge circuits.

Thus, this is all about an overview of the buffer amplifier or voltage follower. It is a non-inverting and unity gain buffer, that uses a single operational amplifier. These have two characteristics like input impedance is high and output impedance is low. They strengthen the signal by allowing high impedance sources & drive a less impedance load. This uses an operational amplifier where its design should be specified like a unity-gain stable. By using external transistors, the creation of a unity gain driver with high current can be done in its design. Here is a question for you, what are the disadvantages of voltage follower?

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