Why differential amplifier is used

The basic non inverting amplifier is shown in fig. The gain of the non inverting amplifier circuit of the operational amplifier is easy to determine and the output of the non inverting amplifier is same as the input voltages. So, that the gain of the amplifier is exceedingly high. As the input to the op amp draws no current this means that the current flowing in the resistors R1 and R2 and the voltage at the both inputs is same.

A voltage follower is also called as a unity gain amplifier, a buffer amplifier and an isolation amplifier is an op-amp circuit which has a voltage gain of 1. This means that the op amp does not provide any amplifications to the signal. The reason it is called as a voltage follower is because the output voltage does not provide the input voltage. An op-amp circuit is very high input impedance. This high input impedance is a reason voltage follower is used. The load demands and draws a huge amount of current.

By connecting one input to a fixed voltage and the other to a thermistor or a light-dependent resistor , the differential amplifier circuit detects high or low levels of temperature or intensity of light as the output voltage becomes a linear function of the changes in the active leg of the resistive bridge network.

A Wheatstone Bridge Differential Amplifier can also be used to find the unknown resistance in the resistive bridge network, by comparing the input voltages across the resistors. The voltage V 2 is determined by the variable resistor V R1. The resistors R 1 and R 2 act as a potential divider network.

A fixed reference voltage is applied to the inverting input, through R 1 and R 2. The same circuit can be modified to detect variations in temperature, simply by replacing the LDR with a Thermistor.

By interchanging the positions of LDR and V R1 , the circuit can be made to detect dark or light or heat or cold in case of a thermistor. The differential gain of the amplifier is and the value of CMRR is. Your email address will not be published. Differential Amplifier. April 21, By Ravi Teja. In dB,. For an ideal amplifier CMMR should be practically infinite but in actual practice, it is not so and has a finite value.

It is defined as the ratio of the desired signal to the undesired signal. The larger the CMMR the better is the amplifier. The differential amplifier can also be a differential voltage comparator where it compares one input signal with the other.

Suppose we connect one input to a fixed reference voltage and the other to a Light Dependent Resistor or to a thermistor. We can detect a low or high level of light. This is so because now the output voltage will be a linear function of changes in the bridge circuit.

The construction of Differential Amplifier is used in all those circuits where low drift is very important. Such as stages of Oscilloscope and electronics voltmeter. Your email address will not be published. Below there is a figure presenting differences between a fully-differential and a standard operational amplifier. There are two input, one reference and one ground electrodes attached to the skin.

It is very important because it amplifies the differential signal of interest and rejects the common mode voltages at the same time. WikiLectures WikiLectures. Personal tools Not logged in Talk Contributions Log in.