Question

For the circuit shown below
The value of voltage, V in the circuit is

• A. 3.33 V
• B. 10 V
• C. 0 V
• D. 1.33 V

Answer 1

The correct option is A 3.33 V

we assume that both diodes are conducting. then voltage at point -B, $V_B=0$ and $V=0$. The current in $D_1$ is obtained from
$I_{D1}=\frac{10-0}{5}=2mA$
The node equation at B is
$I_{D2}+2=\frac{0-(-10)}{10}$
Which yeilds $I_{D2}=-1mA.$ Since this is not possible our assumption is not correct. We start again assumption that $D_2$ is off and $D_1$ is on. The current $I_{D1}$ is given

$I_{D1}=\frac{10-(-10)}{15}=1.33mA$
and the voltage at nodes-B is
$V_B=-10+10\times 1.33=+3.3V$
Thus $D_2$ is reversed biased as assumed and the final result is $V=3.33V.$