Two identical p-n junction diodes are connected with a battery in the three different ways shown in the figure. In which of them will the potential difference across the two diodes be identical?

Question

Accepted Answer

(2) For circuit (2) and (3). Idea: two identical diodes in series always carry the same current, so they drop the same voltage whenever they are in the same state, both conducting or both blocking. They differ only when one conducts and the other blocks. Circuit (2): both diodes point the way the battery drives the current, so both are forward biased. Each drops the same forward voltage, about 0.7 V for silicon. Equal. Circuit (3): both point against the current, so both are reverse biased. Only the tiny leakage current flows, and by symmetry the battery voltage divides equally between two identical junctions. Equal. Circuit (1): the diodes face opposite ways, so one is forward biased and the other reverse biased. The blocking one takes almost the whole battery voltage while the conducting one drops a few tenths of a volt. Unequal. So the potential differences are identical in circuits (2) and (3).

Two identical p-n junction diodes are connected with a battery in the three different ways shown in the figure. In which of them will the potential difference across the two diodes be identical?

Step-by-step solution

Why the other options are wrong