How does a real diode differ from an ideal diode?

How does a real diode differ from an ideal diode?

• A. Forward voltage drop and reverse leakage
• B. No forward drop and infinite reverse resistance
• C. No current
• D. Infinite conduction

Answer: (A)

Real diodes differ from an ideal diode in two main ways: they have a finite forward voltage drop and a nonzero reverse leakage current. When you forward-bias a real junction, it needs around 0.6–0.7 volts (for silicon) before it conducts significantly, because the p-n junction presents an energy barrier and the current rises according to the diode equation as the voltage climbs above that threshold. Even when the diode is reverse-biased, a small current flows due to minority carriers and other leakage paths—the reverse leakage current. The ideal diode model, by contrast, assumes zero forward voltage drop when conducting and zero current (infinite resistance) when reverse-biased, which is not how real devices behave. The other options imply no forward drop, no leakage, no current, or infinite conduction, none of which match real diode behavior.

Real diodes differ from an ideal diode in two main ways: they have a finite forward voltage drop and a nonzero reverse leakage current. When you forward-bias a real junction, it needs around 0.6–0.7 volts (for silicon) before it conducts significantly, because the p-n junction presents an energy barrier and the current rises according to the diode equation as the voltage climbs above that threshold. Even when the diode is reverse-biased, a small current flows due to minority carriers and other leakage paths—the reverse leakage current. The ideal diode model, by contrast, assumes zero forward voltage drop when conducting and zero current (infinite resistance) when reverse-biased, which is not how real devices behave. The other options imply no forward drop, no leakage, no current, or infinite conduction, none of which match real diode behavior.