Question

For the following circuit, assuming the op-amp is ideal, find the current through the load (IL) if V1=3.7V, V2=2V, R1=1.5KΩ, R2=8.5KΩ, R3=1 KΩ, R4=39 KΩ and RL=2.3KΩ.

RL R4 w n w n + R1 +1 V1 R2 R3 } > +1 V2

Consider the same circuit as in with Question 1, but with the following new component values: V1=3.7V, V2=6V, R1=1.5KΩ, R2=8.5KΩ, R3=1 KΩ, R4=39 KΩ and RL=2.3KΩ. What is the input impedance as seen by the source V1?

Answer 1

I have solved your problem which is shown below:

+ vo v. Ru Vi= 3.70 R32 462 V2 z 2V R 4 2 3gkuh R, 21.Skr R22.3k 2 R2 = 8. Skr Using Kinchofs Law node A Varo R2 at varu, R Ub-V2 R3 vo-vo Ru So Purt values in we get Va + va-3.7 8.5 15 va + I 1.5 3 . 3.1 8.5 ل 1.5 Va co. 7843] 2 37 is Vaz 37 3.145V Ist 0.7843

In OPAMP Va=ub Put value in to get to 3.145-2 + 3.145-vo o P 8.5 kr 3912 0.1347 + 0.0806 vo 39kn 0.2153 = vo 39 Vo= 39+ 0.2153 vo 28.39 U To Fund current [La vo 8.39 2.3kr 19.31m mA Ruk Part (2) To determine Inpurt impeden u. Zin Vir Iin Vina Va Apply Kuchols rule at A we get U Varui Ri & Va 0 d R2

Va - 3.1 + va 8.5 o 1 1.sk t inlo 3:7 1.5 8.5 Va 32 { it's + s] = Van 3.145V = Vin 37 TS 80.78 43 Using formule Vina vil zin Rit Rin Vis Zin Vi Ri+Zin 3.145 Zus 1.572 in 3.7

0.85 = Zus 1.s+Zin 0.85 (list Zur )= Zini 1.275+ 0.85 Zin - Zin 1:275: o.152 in Zina 0.85 kn across vi

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