NEIEP Mechanics Practice Exam

What is the voltage drop across a silicon diode that is forward biased?

1. 0.3 volts

2. 0.5 volts

3. 0.7 volts

4. 0.9 volts

The correct answer is: 0.7 volts

A silicon diode, when forward biased, typically exhibits a voltage drop of approximately 0.7 volts. This characteristic voltage drop occurs due to the properties of silicon material and the energy required for charge carriers (electrons and holes) to move through the p-n junction. In a forward-biased condition, the silicon diode allows current to flow, but there is still some resistance encountered at the junction, which results in this voltage drop. The 0.7 volts is a standard value widely accepted in the field of electronics for silicon-based diodes, particularly in typical low-power applications. Other values listed in the options, such as 0.3 volts or lower, are more representative of germanium diodes, which have a lower forward voltage drop. Values like 0.9 volts might be applicable in some specialized high-power conditions but are not representative of a standard silicon diode under normal operating conditions. Understanding these voltage characteristics is crucial for designing circuits involving diodes, ensuring proper biasing and operation within the correct voltage range.