Which statement about diode forward voltage drops is correct?

• A. Germanium diodes have a lower forward voltage drop than Silicon diodes.
• B. Silicon diodes have a lower forward voltage drop than Germanium diodes.
• C. Both diodes have the same forward voltage drop.
• D. Germanium diodes never conduct.

Answer: (A)

Forward voltage drop is determined by the semiconductor material when a diode is forward biased. Germanium has a smaller bandgap than silicon, so it requires less forward voltage to start conducting. In practice, germanium diodes turn on around 0.2–0.3 V, while silicon diodes need about 0.6–0.7 V. That’s why germanium diodes have a lower forward voltage drop than silicon diodes.

This means germanium diodes do conduct, but with a smaller voltage drop, which can be advantageous in low-voltage circuits. Keep in mind Ge diodes typically have higher leakage and are more temperature-sensitive, which is why they’re used less often today. The other statements aren’t correct: silicon diodes do not have the lower drop, the drops aren’t the same, and germanium diodes do conduct forward-biased.