Problem 15-15    Source:    Problem 7 - página 23 - PERIS, César F. & RIPOLL, M. A. Vicente    Book: 150 Problemas de Teoria de Circuitos - 2004.

Determine the equivalent Thévenin and Norton at terminals a-b of the circuit shown in Figure 15-15.1.

Solution of the Problem 15-15

First, let's determine the Thévenin equivalent of the circuit highlighted by the orange rectangle. Thévenin's voltage is given by:

Thévenin's resistance is given by the parallel of the two resistors, or:

From these data, we can calculate the value of I_B . So:

After calculating the I_B , we know the value of the dependent voltage source (right side of the circuit), which is equal to V = 90 (mA) x 1000 = 90 volts . Now we can calculate the Thévenin equivalent from the point of view of the a-b terminals. For this, we will calculate the open circuit voltage that is given by:

Now we must calculate the short-circuit current at the a-b terminals. Shorting the terminals a-b eliminates the resistor of 225 Ω, so we have:

So the resistance of Thévenin will be:

So we have: