Question 3: Semiconductors and Logic Gates

Question

Assuming in forward bias condition there is a voltage drop of 0.7 V across a silicon diode, the current
through diode $D_{1}$ in the circuit is ______ mA.$\$

(Assume all diodes in the given circuit are identical)

Accepted Answer

Diode $D_{1}$ and $D_{3}$ are forward bias and $D_{2}$ is reverse bias $\$  
Therefore , the total current flows through the resistor $ R_1 = 0.3	ext{k}\Omega $ is , $\$
Using Ohm’s Law: $\$

$\Rightarrow V_{R1} = V_{	ext{source}} - V_d $ $\$

$V_{R1} = 12	ext{V} - 0.7	ext{V} = 11.3	ext{V}$ $\$

So, the total current is $\$

$i_{	ext{total}} = \frac{V_{R1}}{R_1} = \frac{11.3}{0.3	ext{k}\Omega}$ $\$

$\Rightarrow i_{	ext{total}} \approx 37.7	ext{mA}$ $\$

The total current  $I_{	ext{total}}$ reaches the parallel junction and splits between the two forward-biased diodes $D_{1}$ and $D_{3}$. Since the diodes are identical, the current divide equally:$\$

$i_{D1} = \frac{I_{	ext{total}}}{2}$ $\$

$\Rightarrow i_{D1} = \frac{37.7}{2} \approx 18.8	ext{mA}$ $\$

Hence, the correct option is (B).

Answer

17.6

Answer

18.8

Answer

20.15

Answer

11.7

Semiconductors and Logic Gates

Assuming in forward bias condition there is a voltage drop of 0.7 V across a silicon diode, the current through diode D_{1} in the circuit is ______ mA.\\ (Assume all diodes in the given circuit are identical)

Choose the correct answer: