Updated: Dec 9, 2025 | Source: 2023-2027 Question Pool | Topic: G6A
G6A05G6A

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

Deep Dive: G6A05

The correct answer is C: 0.7 volts. The approximate forward threshold voltage of a silicon junction diode is 0.7 volts. Silicon diodes are the most common type and have this standard forward voltage. For amateur radio operators, this is a fundamental value. Understanding this helps when designing circuits.

Why Other Answers Are Wrong

Option A (0.1 volt): Incorrect. 0.1 volt is too low - that's more like Schottky diodes. Silicon junction diodes are 0.7V. Option B (0.3 volts): Incorrect. 0.3 volts is for germanium diodes, not silicon. Silicon has higher forward voltage than germanium. Option D (1.0 volts): Incorrect. 1.0 volt is too high - that's more like LED forward voltage. Silicon junction diodes are 0.7V.

Exam Tip

Silicon diode forward voltage = 0.7 volts. Think 'S'ilicon = 'S'even-tenths volt (0.7V). Silicon junction diodes have standard 0.7V forward voltage. Not 0.1V, not 0.3V (germanium), not 1.0V - just 0.7V.

Memory Aid

Silicon diode forward voltage = 0.7 volts. Think 'S'ilicon = 'S'even-tenths volt. Silicon junction diodes have standard 0.7V forward voltage. Most common diode type.

Real-World Example

You use a silicon diode in a rectifier circuit. The diode starts conducting at about 0.7 volts forward voltage. This is the standard forward voltage for silicon junction diodes - the most common type. Silicon's 0.7V forward voltage is a fundamental value.

Source & Coverage

Question Pool: 2023-2027 Question Pool

Subelement: G6A

Reference: 2023-2027 Question Pool · G6 - Circuit Components

Key Concepts

Silicon diode Forward threshold voltage 0.7 volts Diode characteristics

Verified Content

Question from the official FCC General Class pool. Explanation reviewed by licensed amateur radio operators and mapped to the G6A topic.