Question

Three silicon diodes connected parallel to each other as shown. Forward voltage of diode is 0.7 V. Find current through diode A : 

• A. \(\frac{113}{3}\)mA
• B. \(\frac{113}{6}\)mA
• C. \(\frac{113}{9}\)mA
• D. \(\frac{226}{3}\)mA

Hint:

Always check the orientation of diodes first. A reverse-biased diode (like B here) is effectively invisible to the current, simplifying the parallel branches.

Answer 1

The Correct Option is B

To find the current through diode A, let's analyze the given circuit with the three silicon diodes connected in parallel. The forward voltage across each diode is given as 0.7 V.

Here is the step-by-step solution:

1. Since the diodes are in parallel, the forward voltage across each diode in the parallel configuration is the same, i.e., 0.7 V.
2. Assume the total supply voltage is \( V_s \), and the total current delivered to the circuit, \( I_t \), splits equally among the three identical diodes due to their parallel arrangement and identical characteristics.
3. The current through each diode can be approximated using the equation:

\(I_d = \frac{V_d}{R_d}\), where:

• \(I_d\) is the current through the diode.
• \(V_d\) is the voltage across the diode (0.7 V).
• \(R_d\) is the dynamic resistance of the diode. We may assume ideal behavior if not specified.

1. The current source supplies a total current of \(I_t\). As these diodes are identical, this current is evenly divided among the three:

\(I_t = 3 \times I_d \, \Rightarrow \, I_d = \frac{I_t}{3}\)

1. Substitute this into the equation for the diode given the voltage:

Given \( V_d = 0.7 \, \text{V} \) and assuming ideal behavior, you are provided with the current through the source as \(\frac{113}{2} \, \text{mA}\).

1. The current through diode A, using the distribution of current (\( \frac{I_t}{3} \)), will be:

\(I_{\text{diode A}} = \frac{\frac{113}{2} \, \text{mA}}{3} = \frac{113}{6} \, \text{mA}\)

1. Thus, the current through diode A is indeed \(\frac{113}{6} \, \text{mA}\), verifying the correct option.