Differential amplifiers are one of the most commonly use circuit building blocks in analogue integrated circuits (Analogue Devices, CHAPTER 12: DIFFERENTIAL AMPLIFIERS, 2015). A differential amplifier mainly has two inputs, one inverting and one non-inverting. Recent amplifier devices are now made to lie on a single chip. Inside the chip, the positive and the negative signals are added, which further becomes a single output. The difference between both the input voltages becomes amplified. In this case if there is any common-mode voltage, it is rejected and does not become a part of the output (Test and Measurement Tips, DIFFERENTIAL AMPLIFIER BASICS, 2015).


Differential amplifiers are used in numerous applications, but are prime components of systems that are utilized for audio controlling. The following sections talk more on this subject.


Volume Control using Differential Instrumentation Amplifier

Differential amplifiers have a significant application in the form of basic volume control in audio systems. Thus, these amplifiers can be used in remotes controlling audio, speakers, PA systems, guitar amplifiers, and other such devices.


When the differential amplifier is used for controlling audio, a signal is applied to one end of a potentiometer in the circuit. The other end is grounded. After this, a mechanical slider is made to move between the lengths of the potentiometer’s resistance. This action leads to the creation of an adjustable voltage divider (Play Hookey, SOME APPLICATIONS FOR DIFFERENTIAL AMPLIFIERS, 2015). There is no specific position to which the slider moves along the resistance pathway. As soon as the divider is created, the slider is said to be in the correct position. The output audio signal now has a reduced amplitude signal, even though it is a copy of the former one.


A stereo audio system would mainly have two of the differential amplifiers. One amplifier is present for each audio channel. These audio channels are mechanically connected so that they can function in unison.


Minor Problems of Differential Amplifiers used for Audio Control

The use of differential amplifiers for audio control might project a few problems of its own. For example, as the movable contact has to slide directly on the material under it that provides resistance. This may cause some wear and tear of the contact, especially after being used for a long time. When the contact is under an exposed condition, a lot of dirt and dust may accumulate. This could lead to loss in signal quality and cause the output to be noisy as a result of dust interference (Play Hookey, SOME APPLICATIONS FOR DIFFERENTIAL AMPLIFIERS, 2015). These effects may be visible when audio systems are used for numerous years, after which their quality drops.


Differential amplifiers are just one individual class of components included under the category of RF measurement equipment.  Apart from these objects, there also are others like RF shield boxes, RF Switches, tunable amplifiers, etc. that are utilized for numerous applications. Some of these applications involve radio communications, military communications, medical uses, and many more.


Author Name: Oscar Jenson


Disclaimer – “The above opinions are purely a reflection of the author’s point of view. They do not reflect the position of Ranatec.”