Question

In the circuit shown in figure, the silicon and germanium diodes start conducting at $0.7 \,V$ and $0.3 \,V$ respectively. What are the values of $V_0$ and $I$ ?

• A. $12 \,V, 2.4 \,mA$
• B. $11.7\, V, 2.34 \,mA$
• C. $11.3 \,V, 2.26\, mA$
• D. $11\, V, 2.2 \,mA$

Answer 1

Answer: (B)

The germanium diode will start conducting before the silicon diode does so. The voltage across $Ge = 0.3\, V$. The output voltage $V_0$ is the voltage across
$R = 12 - 0.3 = 11.7 \, V$
The current $I = \frac{11.7\,V}{5\,k\Omega}$
$=\frac{11.7}{5\times 10^3}$
$= 2.34 \times 10^{-3}\,A$
$ = 2.34\,mA$