summary
● A junction diode is created by joining N-type and P-type materials together.
● The region near the junction is referred to as the depletion region. Electrons cross the junction from the N-type to the P-type material, and thus both
the holes and the electrons near the junction are depleted.
● The size of the depletion region is limited by the charge on each side of the junction.
● The charge at the junction creates a voltage called the barrier voltage.
● The barrier voltage is 0.3 V for germanium and
0.7 V for silicon.
● A current flows through a diode only when the external voltage is greater than the barrier voltage.
● A diode that is forward biased conducts currenta. The P-type material is connected to the positive terminal, and the N-type material is connected to the negative terminal.
● A diode that is reverse biased conducts only a small leakage current.
● A diode is a one-directional device.
● The manufacturer specifies a diode’s maximum forward current and reverse voltages.
● The schematic symbol for a diode is
● In a diode, the cathode is the N-type material, and the anode is the P-type material.
● Diodes can be constructed by the grown junction, alloyed junction, or diffused junction method.
● The diffused junction method is the one most often used.
● Packages for diodes of less than 3 A identify the cathode end of the diode with a black, white, or silver band.
● A diode is tested by comparing the forward to the reverse resistance with an ohmmeter.
● When a diode is forward biased, the resistance is low.
● When a diode is reverse biased, the resistance is high.