Ham Radio General Class Practice Test

What is the approximate junction threshold voltage of a germanium diode?

1. 0.1 volt

2. 0.3 volts

3. 0.7 volts

4. 1.0 volts

The correct answer is: 0.3 volts

The junction threshold voltage of a germanium diode is approximately 0.3 volts. This characteristic voltage is crucial for understanding how germanium diodes operate in electronic circuits. When a forward voltage of around 0.3 volts is applied, the diode begins to conduct significantly. This lower threshold compared to silicon diodes, which typically have a junction threshold of about 0.7 volts, is why germanium diodes can be favored in specific applications such as low-voltage or low-power circuits. The semiconductor properties of germanium lend themselves to this lower conduction threshold, making it valuable for certain types of signal processing and audio applications where minimal forward bias is needed to initiate conduction.