Diode Theory Operation and Use of Semiconductor Devices Cleveland Institute of Electronics Diode Theory Lesson Request a Free Catalog Diode Theory • What is a diode, or semiconductor for that matter? • If a conductor is suppose to conduct current does that mean a semiconductor partially conducts current? • A diode is a device that acts like a conductor since it allows current to pass in one direction (known as FORWARD BIASING) and it acts as an insulator since it blocks current passing in the opposite direction (known as REVERSE BIASING). Diode Theory • The diode is comprised of a P-type material combined with an N-type material such as: • Current flows from the negative terminal of the battery to the N-type and on through the P-type and then returns to the positive terminal of the battery. Diode Theory • When the diode is at rest it will look like: • The P-type consists of Holes or + charged particles. • The N-type consists Of Free Electrons or – Charged particles. Diode Theory • Diode as a Conductor • When a voltage is applied current will flow. • This causes the Holes to move toward the Depletion Region and the Free Electrons to move toward the Depletion Region. The Depletion Region shrinks allowing current to flow. This is Forward Bias. Diode Theory • We will look at the diode as an insulator • When the battery polarity is reversed, the Holes move away from the Depletion Region as does the Free Electrons expanding the Depletion Region thus restricting the movement of current. This is Reverse Biasing Diode Theory • The schematic symbol for a diode and how to identify a diode. Diode Theory • In our discussion, we have indicated that current flows from cathode to anode. • This is for Electron Current Flow but for those using Conventional Current Flow, it is opposite. Diode Theory • Diodes are also know as Rectifiers, changing AC current into DC current in a power supply. Diode Theory The End .