Question

Ge and Si diodes conduct at 0.3 V and 0.7 V respectively. In the following figure if Ge diode connection is reversed, the value of V${}_0$ changes by

• A. 0.2 V
• B. 0.4 V
• C. 0.6 V
• D. 0.8 V

Answer 1

The correct option is B 0.4 V

Consider the case when $Ge$ and $Si$ diodes are connected as shown in the figure.

Equivalent voltage drop across the combination $Ge$ and $Si$ diode $=0.3V$

$\Rightarrow$ Current $i=\frac{12-03}{k\Omega }=2.34mA$

$\therefore$ Out put voltage $V_0=Ri=5k\Omega \times 2.34mA=11.7V$

Now consider the case when diode connection are reversed. In this case voltage drop across the diodes combination $=0.7V$

$\Rightarrow$ Current $i=\frac{12-0.7}{5k\Omega }=2.26mA$

$\Rightarrow V_0=iR=2.26mA\times 5k\Omega =11.3V$

Hence charge in the value of $V_0=11.7-11.3=0.4V$