Problem 47-3    Source:   Problem 5.62 - page 185 -    ALEXANDER, Charles K., SADIKU, Matthew N. O. -    Book: Fundamentos de Circuitos Elétricos - 5ª Edição - Ed. McGraw Hill - 2013.

Determine the voltage gain K = V_o / V_i, of the circuit shown in the Figura 47-03.1.

Solution of the Problem 47-3   

Through the circuit OP 2 is in the non-inverting configuration. Therefore, we can determine the relationship between V_o and V_x. Logo:

The OP 1 is in the adder configuration, where one of the input voltages is V_i and the other, V_o. Thus, it can be written that:

Substituting in the first equation, this value found, we obtain:

The gain of the circuit will be given by:

Where K is the voltage gain of the circuit.