Problem 42-1    Source:  Example 5-1 - page 157 - ALEXANDER, Charles K., SADIKU, Matthew N. O. - Book: Fundamentos de Circuitos Elétricos - 5ª Edição - Ed. McGraw Hill - 2013.

An opamp LM741 has an open mesh voltage gain of 2 x 10⁵ input resistance of 2 MΩ and output resistance of 50 ohms . The configuration circuit is shown in Figura 42-01.1, where R_f = 20 kΩ and R_i = 10 kΩ. Use the real model of an opamp.

a) Determine the gain of closed loop, V_o / V_s.

b) Determine the current i₂ when V_s = 2 volts.

Problem 42-2    Source:   Problem 4-21 - page 211 - THOMAS, Roland E. , ROSA, Albert J. , THOUSSAINT, Gregory J. -   Book: The Analysis & Design of Linear Circuits - 6ª ed. - Ed. John Willey & Sons, Inc. - 2009.

In the circuit shown in the Figura 42-02.1 determine V_o in function of V_a.

Problema 42-3    Source:   Problem 4-33 - page 212 - THOMAS, Roland E. , ROSA, Albert J. , THOUSSAINT, Gregory J. -   Book: The Analysis & Design of Linear Circuits - 6ª ed. - Ed. John Willey & Sons, Inc. - 2009.

In the circuit shown in the Figura 42-03.1, determine:

a) Using nodal analysis, compute K or the relation V_o / V_s

b) Select values for the resistors in such a way that K= - 3.

Problem 42-4    Fonte:   Problem elaborated by the author of the site.

For the circuit shown in the Figura 42-04.1, calculate the gain of the circuit when the key S is in the position 1 and in the position 2, considering that R = 1000 Ω , R₁ = 2000 Ω , R₂ = 3000 Ω and R₃ = 6000 Ω.