Problem 61-3    Source:  Problem elaborated by the author of the site.

Determine the current I_D in the circuit show in Figure 61-03.1, considering R₁ = R₂ = 200 Ω and R₃ = 330 Ω. We know that V = 24 V and V_D = 0.7 V.

Solution of the Problem 61-3   

Initially we will calculate the Thévenin equivalent for the point a. Calculating the voltage V_th in open circuit we have

Now let's calculate the Thévenin resistance. For this, we put the source V in short circuit, leaving both resistors in parallel. So

With this data, let's redraw the circuit as shown in Figura 61-03.2, or

Analyzing the circuit, one can write the equation that determines the current in the diode, or:

Doing the numerical substitution and performing the calculation, we find