electrical4u.com logo Home MCQ Engineering Calculators Videos Basic Electrical Circuit Theories Electrical Laws Materials Batteries Illumination Generation Transmission Distribution Switchgear Protection Measurement Control System Utilities Safety Transformer Motor Generator Electrical Drives Electronics Devices Power Electronics Digital Electronics Biomedical Instrumentation

Difference Amplifier or Op Amp Subtractor

Published on 24/2/2012 and last updated on 5/9/2018
A difference amplifier or op amp subtractor is a specially designed op amp based amplifier circuit, which amplifies the difference between two input signals and rejects any signals common to both inputs.
Difference Amplifier or Op Amp Subtractor Let us consider the above op amp circuit. Now, by applying Kirchhoff Current Law at node 1, we get,

We have written this equation by assuming that there is no current entering in the inverting terminal of the op amp. Now, by simplifying the above equation, we get,

Now, by applying Kirchhoff Current Law, at node 2, we get, We know that, in ideal op amp, voltage at inverting input is same as the voltage at non inverting input. Hence,

So, now from equation (i) and (ii), we get,

The difference amplifier must reject any signal common to both inputs. That means, if polarity and magnitude of both input signals are same, the output must be zero. This condition must be satisfied only when, In that case, equation (iii) becomes, Again, if we make, R1 = R2, then equation (iv) becomes, So, if R1 = R2 and also R3 = R4 then the difference amplifier becomes a perfect subtractor, which subtracts directly the input signals. Finally, the circuit of op amp substractor becomes, op amp substractor

Related pages
Difference Amplifier or Op Amp Subtractor
Please Rate this Article
1
⚑ 1 total
5
4
3
2
1


New Articles
Articles on Op-amp
Op-ampOp amp 741 ICIdeal Op AmpClosed Loop Gain Inverting Op AmpNon Inverting Op AmpOp Amp AdderOp Amp SubtractorOp Amp DifferentiatorOp Amp IntegratorOp Amp CharacteristicsOp Amp CircuitApplications of Op Amp
More Articles on Circuit Theory
Circuit and NetworkCircuit TheoremCircuit AnalysisTwo Port NetworkRL CircuitMatrixRLC Circuit
Articles Categories
Home
Basic Electrical
Electric Transformer
Electric Generator
Electric Motor
Electrical MCQ
Engineering Calculators
Video Lectures
Electrical Generation
Electric Transmission
Switchgear
Electric Protection
Electrical Measurement
Electronics Devices
Power Electronics
Digital Electronics