Op-amp as difference amplifier(sub-tractor)
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1) This is the circuit for op-amp as sub-tractor.
2) To find the output voltage ,the superposition theorem is used.
3) It states that, when there are multiple input sources, the output voltage of that circuit can be determined by summing the individual responses achieved by considering each voltage source acting separately.
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..............Thus op-amp will act as sub-tractor
Example:
Q) Find output voltage using superposition theorem.
--->The values given are
V1=2,V2=5
R1=2 Kohm, R2=2 Kohm,
R3=10 Kohm, R4=4 Kohm
Sol: when V1 is active ;Vout1=-10V
When V2 is active ; Vout2=20
Adding Vout1 and Vout2
Vout =10 V
When all the resistances are made equal then
Vout= V2-V1
Vout=3