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- Homework Statement
- Find the Op-amp output voltage Vo in the following circuit.
- Relevant Equations
- Vout= Vin(1+Rf/R1) for non-inverting input.
Here is the circuit diagram provided in the book.
In the solution, the book has used the following approach (red markings in the image):
Input to the left transistor is 2V. Considering base-emitter junction drop to be 0.7V, the emitters are at 1.3V (left red arrow). Now, using the "virtual short" concept, the base of the right transistor is also pulled to 2V.
As the non-inverting terminal of op-amp is at 2V, using Kirchhoff's rules and the feedback equation, Vout=4V.
But how is the base of the right transistor pulled to 2V? Is the concept of "virtual short" really applicable here? As per my understanding, the right transistor should be cut off.
What is wrong here?
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