Resolved Problems about Multiple Operational Amplifier

Problem 47-2 Source: Problem 5.74 - page 186 - ALEXANDER, Charles K., SADIKU, Matthew N. O. - Book: Fundamentos de Circuitos Elétricos - 5ª Edição - Ed. McGraw Hill - 2013.

Determine the current I in the circuit shown in the Figura 47-02.1.

Solution of the Problem 47-2

In order to determine the current I, we must calculate the value of V₁ and V₂. The two circuits are in the configuration inverter. Calculating the voltage V₁:

V₁ = - (100 / 10) 0.9 = - 9 V

Calculating the value of V₂:

V₂ = - (32 / 1.6) 0.6 = - 12 V

In possession of the value of V₁ and V₂, we can calculate the value of I. Like this:

I = (V₁ - V₂)/ 20 kΩ = [- 9 - (-12)] / 20 kΩ

Performing the calculation we find:

I = 150 µA

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