Ham Radio General Class Practice Test

What is the approximate junction threshold voltage of a conventional silicon diode?

1. 0.1 volt

2. 0.3 volts

3. 0.7 volts

4. 1.0 volts

The correct answer is: 0.7 volts

The approximate junction threshold voltage of a conventional silicon diode is around 0.7 volts. This voltage is important because it represents the minimum forward voltage that must be applied to the diode for it to conduct current effectively. When the voltage across the diode reaches this threshold, it allows current to flow from the anode to the cathode, thus enabling the diode to operate in its forward bias region. Silicon diodes exhibit this characteristic due to the properties of silicon as a semiconductor material, which requires a certain level of energy (in the form of voltage) to overcome the potential barrier at the p-n junction. This behavior is well-established in electronics and is fundamental to understanding how diodes function within circuits. Other options provided do not accurately reflect the threshold voltage for silicon diodes. For instance, values like 0.1 volts or 0.3 volts are significantly lower than the typical forward voltage drop of silicones, while 1.0 volts exceeds the common threshold and is often associated with other specific diodes, such as Zener diodes under reverse bias conditions. Understanding that 0.7 volts is the standard helps in designing circuits that involve silicon diodes and predicting their behavior in different applications.