Chapter 1, Problem 21P

A linear model of a diode is shown in Fig. P1.21. where $R_d$ is the forward resistance of the diode and $V_{on}$ is the voltage that turns the diode ON. To determine the resistance $R_d$ and voltage $V_{on}$, two voltage values are applied to the diode and the corresponding currents are measured. The applied voltage $V_s$ and the measured current I are given in Fig. P1.21. The applied voltage and the measured current satisfy the linear equation $V_s=I{R}_d+V_{on}$. (a) Find the equation of the line for $V_s$ as a function of I and determine the resistance $R_d$, and the voltage $V_{on}$.

(b) Sketch the graph of $V_s$ as a function of I. and clearly indicate the resistance $R_d$ and the voltage $V_{on}$ on the graph.