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

A silicon junction diode requires a minimum forward voltage to overcome the PN junction's depletion region before it allows significant current to flow. For standard silicon diodes, this physical threshold is universally approximated as 0.7 volts. It is important to distinguish this from germanium diodes, which have a lower forward voltage drop of about 0.3 volts. Remembering the 0.7-volt rule is essential for calculating voltage drops in power supplies and basic transistor amplifier circuits.