Answer to Question #187244 in Electrical Engineering for elie

Question

https://www.chegg.com/homework-help/questions-and-answers/use-iterative-analysis-procedure-determine-diode-current-voltage-circuit-fig-310-vdd-1-v-r-q3166612

Answer 1

Since the voltage across the diode is $V_D=0.7V$, the current through the loop is obtained by using the relation for the current $I_D=\frac{V_{DD}-V_D}{R}$  

To begin the iteration, we assume that $V_D=0.7V$

Substituting the values $V_{DD}= 1V, R=1k \Omega; V_D=0.7V$ in the relation for the current gives,

$I_D=\frac{V_{DD}-V_D}{R}=\frac{1-0.7}{1000}=0.3mA$

From the relation for the diode current, I_D given by $I_D=I_se^{\frac{V_D}{V_T}}$ , we get the relation for V_D as $V = 0.025 \ln({\frac{I_D}{I_S}})$

Substituting the values I_D= 0.3mA, I_S=10^-12mA in the relation for the voltage gives $V_D = 0.025 \ln({\frac{I_D}{I_S}})= 0.025 \ln({\frac{0.3}{10^{-12}}})=0.66V$

Now find the current by substituting the values V_D= 0.66V; V_DD= 1 and R = 1$k\Omega$ in the relation $I_D= {\frac{V_{DD}-V_D}{R}}= {\frac{1-0.66}{1000}}=0.3392 A$

On substituting the value of I_D= 0.34 mA and /, = 10^-12mA in the relation for the voltage, $V=0.025 \ln \frac{I_D}{I_S}$ , we get the value for voltage, V.