Q 12-14-176JEE MainJEE Main 2019 (9 Jan, Shift 2)Medium
Ge and Si diodes start conducting at $0.3\ \text{V}$ and $0.7\ \text{V}$ respectively. In the following figure if the Ge diode connections are reversed, the value of $V_0$ changes by: (assume that the Ge diode has large breakdown voltage)
Answer: (B) $0.4\ \text{V}$
Initially both diodes are forward biased. The Ge diode switches on first at $0.3\ \text{V}$ and holds the voltage across the pair at $0.3\ \text{V}$, so the Si diode never conducts:
$$V_0 = 12 - 0.3 = 11.7\ \text{V}$$
With the Ge diode reversed it blocks, and current flows through the Si diode:
$$V_0 = 12 - 0.7 = 11.3\ \text{V}$$
$V_0$ changes by $0.4\ \text{V}$.
Solution by Sreeraj P, M.Sc Physics