Difference Between Differential Amplifier and Operational Amplifier

Main Difference – Differential Amplifier vs. Operational Amplifier

Amplifiers are extremely vital components in electronic circuits. The main difference between differential amplifier and operational amplifier is that a differential amplifier is an amplifier that amplifies a voltage difference between its inputs, whereas an operational amplifier is, in fact, a type of differential amplifier with a large open-loop gain, a high input impedance and a low output impedance.

What is a Differential Amplifier

A differential amplifier is an electric component which amplifies the difference between two signals applied to two input terminals, while rejecting signals which are common to both the input terminals. A differential amplifier has two inputs: we will refer to these as V_1 and V_2. Suppose the amplifier amplifies V_1 by a factor A_1 and V_2 by a factor A_2. Then, the output voltage V_o would be:


The differential voltage (V_d) is defined as V_d= V_2-V_1\qquad(2)

The common mode voltage (V_c) is defined as V_c=\frac{ V_1+V_2}{2}\Rightarrow 2V_c=V_1+V_2\qquad(3).

Using these two values, we can try to derive an expression for the output voltage.

(2)+(3)\Rightarrow 2V_c+V_d=2V_2\Rightarrow V_2=V_c+\frac{V_d}{2} and,

(2)-(3)\Rightarrow V_d+2V_c=-2V_1\Rightarrow V_1=V_c-\frac{V_d}{2}

Now we can substitute these values back into (1), giving us:

V_o=A_1\left( V_c-\frac{V_d}{2}\right)+A_2\left( V_c+\frac{V_d}{2}\right)

Expanding this and re-factorizing, we get:

V_o=\left( A_1+A_2\right)V_c+\left( \frac{A_2-A_1}{2}\right)V_d

The quantity A_1+A_2 is called the common-mode gain (A_c) and the quantity \frac{A_2-A_1}{2} is called the differential gain (A_d). In terms of these nquantitietwo quantities, we can simply write the above equation as:


What is an Operational Amplifier

An operational amplifier is a type of differential amplifier with high gain. Operational amplifiers have large input impedances and small output impedances. For ideal operational amplifiers, the input impedance is taken to be infinite while the output impedance is taken to be 0. Often, operational amplifiers make use of a resistor to provide itself negative feedback. By changing the value of the resistor, it is possible to change the gain of an operational amplifier. Note that adding a resistor reduces the overall gain of an operational amplifier. When we calculated the gain in the previous section, we did so by assuming there is no feedback. Therefore, the gain we have calculated is the maximum possible gain for an amplifier, and it is called the open-loop gain since there is no feedback mechanism in the system.

Operational amplifiers have an extremely important place in analog computing where they are used to not only amplify signals but to invert voltages, add voltages, and to carry out differentiation and integration.

The figure below shows the symbol for an operational amplifier:

Difference Between Differential Amplifier and Operational Amplifier - Operational_amplifier_symbol

The symbol of an operational amplifier

V_+ and V_- are are the input terminals, while V_{S+} and V_{S-} are the terminals to which a power supply is connected. V_{out} is the output terminal.

The image below shows an operational amplifier:

 Difference Between Amplifier and Oscillator - Op_amp

An operational amplifier

Difference Between Differential Amplifier and Operational Amplifier

differential amplifier is a type of amplifier which amplifies a voltage difference between two of its inputs.

An operational amplifier is a type of differential amplifier with a large open-loop gain, a very high input impedance and a very low output impedance.

Image Courtesy:

“Op-amp pinouts.” by User:Omegatron (Own work) [], via

“Opamp” by lambda’s (Own work) [], via 

About the Author: Nipun

Related pages

purpose of quick ratioexample of monocot and dicot seedsdynamic character literary definitionsnuggle and cuddleunits of entropy and enthalpycharacteristics of a monologuesyntax vs grammarexample of assimilation and accommodationmolecular formula of ascorbic aciddifference between ammeter and voltmeteropen and closed syllables examplesthrombosis atherosclerosisstatic vs kinetic frictiondifference between respiration and photosynthesispolar and nonpolar definitionemf and terminal potential differenceionizing and non ionizing radiationsdefine aliphaticaddition and subtraction of vectors graphical methodmitosis difference in plant and animal cellsexamples of polysemyhyper and hypothyroidismimages formed by concave lensesdefine synthetic rubbercentroidal rotationdifference between imperative and exclamatory sentencesdifference between radicle and plumulecomparison of prokaryotic and eukaryotic cellsdifference between alpha helix and beta pleated sheetmetro monorailrationalism versus empiricismdifference between pi and sigma bondsgerm cells vs somatic cellsallegory symbolfrance popular foodanhydrous diethyl ether molecular weightcold and warm blooded animalsinternational driving permit nrmawhat are different types of nounsenquiry vs inquiry definitiondifference between internal combustion engine and external combustion enginethymine binds withbiannual defineeulogy examples for grandfathergerman shepherd and belgian malinoisliteral and figurative languagedifference between monera and protistadifference between prokaryotic and eukaryotic ribosomesdifference between monarchy and theocracydistillation and evaporationderivation of law of conservation of momentumdifference between a bit and bytethe difference between an alpaca and a llamarespiratory failure ardsdefinition of cold blooded animalsgerund and participle examplesphysical significance of moment of inertiaare scallions onionstwo closed syllablesdefinition for centriolesproperties of saturated and unsaturated fatssynecdoche and metonymydifference between mixtures and pure substanceswhat is the difference between soluble and insolublephagocytosis endocytosisbipolar vs unipolar depressionwhat is the difference between condo and apartmentsillusion vs allusionexplain the difference between a mixture and a compounddifference between stereotype prejudice and discriminationthylakiodflu or food poisoningelectromagnetism and gravityhow to prepare an adjusted trial balance