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# Lecture Notes - Chapter 2

(These Lecture Notes are for courses using the book the Complete Electronics Self-Teaching Guide with Projects. Instructors of courses using that text are permitted to use these Lecture Notes as-is or adapt them for their use).

## Diodes

• Understanding Diodes
•   Discuss semiconductor materials.
• Introduce N and P type semiconductor materials.
• Discuss the structure of a diode (figure 2.3).
• Introduce the term: PN junction
• The P type material is the anode.
• The N type material is the cathode.
• Discuss the flow of electric current through a diode
• Introduce the schematic symbol for a diode (figure 2.4).
• A PN junction conducts electricity in one direction only (figure 2.5).
• Introduce the term: forward-biased diode.
• Introduce the term: reverse-biased diode(figure 2.8).
• Introduce the term: perfect diode.
• Discuss the similarity of a forward-biased diode to a closed switch.
• Discuss the similarity of a reverse-biased diode to a open switch.
• Discuss Project 2-1, The Diode
• Introduce the V-I curve of a diode (figure 2.10).
• Introduce the term: knee voltage (figure 2.16).
• Discuss the use in current limiting resistors.
• Discuss the relationship of knee (or threshold) voltage to the type of semiconductor material used in the diode.
• Introduce the term: voltage drop.
• Circuits with a diode in series with a resistor (figure 2.17).
• Discuss the equation for the voltage drop across the resistor.
• Discuss the equation for the current through the resistor.
• Review the concept that the current through two components in series is equal. Therefore the current through the diode is equal to the current through the resistor.
• Discuss the equation for finding the power dissipated through a diode.
• Circuits with a diode in parallel with a resistor (figure 2.20).
• Discuss the equation for the total current.
• Review the concept that the voltage across components in parallel is equal.
• Discuss the equation for the current through the parallel resistor.
• Discuss the equation for the current through the diode.
• Diode Breakdown
•  Circuits with a reverse-biased diode, in series with a resistor (figure 2.23).
• Discuss the V-I curve for a reverse-biased diode (figure 2.24).
• Introduce the term; Peak Inverse Voltage (PIV).
• Inside the Diode
• Introduce the term; Depletion Region
• Depletion regions act as electrical insulators, preventing the current flow.
• When a diode is forward biased the depletion region shrinks, allowing current flow.
• When a diode is reverse biased the depletion region expands, preventing current flow, unless the peak inverse voltage is exceeded.
• Zener Diodes
•  Zener diodes are reverse biased in circuits (figure 2.26).
• Zener diodes have a precise peak inverse voltage determined by the manufacturer.
• Zener diode placed parallel to a load in circuits to provide a constant voltage, and therefore a constant current across the load (figure 2.29).
• Discuss Project 2.2: The Zener Diode Voltage Regulator
•  Review the circuit (figure 2.33).
• Comment on the expected drop in voltage output (VS) of the 9 volt battery with time.
• Review how VL and IL are expected to remain constant, but IZ is expected to drop as VS drops.

This page includes material extracted, by permission of the publisher, Wiley Publishing, from Complete Electronics Self-Teaching Guide with Projects, ISBN: 9781118217320.