The open voltage is the forward voltage (the current is very small) when the pilot is opened, and the forward voltage is the forward voltage of the rated working current. The open voltage is lower than the forward voltage.
Diodes are also known as crystal diodes, or diodes, and, in addition, early vacuum electronic diodes. It is an electronic device with one - way conduction current. Within the semiconductor diode, there is a PN junction with two lead terminals. The electronic device, in the direction of the external voltage, has the transduction of the unidirectional current. In general, the crystal diode is a p-n junction interface formed by the sintering of p-type semiconductor and n-type semiconductor. The space charge layer forms on both sides of the interface to form the self-built electric field. When the applied voltage is equal to zero, because the p-n junction on both sides of the carrier concentration caused by diffusion and drift caused by self-built electric current is equal in electric equilibrium state and it is also normal diode characteristics.