This document discusses the operational principle of diodes. It begins by introducing diodes and their use to control electric circuit current. Diodes are composed of an anode and cathode and can be modeled as a simple electronic switch. They are made by doping silicon with impurities to create either a p-type or n-type semiconductor, which form a p-n junction when joined. A diode acts as a closed switch under forward bias when positive is applied to the anode, and as an open switch under reverse bias. In the depletion region of a p-n junction, an insulating region is formed. Diodes have applications in rectification circuits and as light sources in LEDs.

1. Diode – Operational
Principle
Yong Heui Cho @ Mokwon University
Some of slides are referred to:
[1] A. S. Sedra & K. C. Smith, Microelectronic Circuits.

2. 2
Electronic Circuits
2. Introduction to Smart Sensors
3. Basic Circuit Theory
4. Diode – Operational
Principle
5. Diode – V/I

3. 3
Diode Circuit
• A diode is widely used to control current o
f electric circuits.

4. 4
Diode
• Diode = anode + cathode
• Simple switch modeling
– Electronic switch

5. 5
Diode Representation
• P-type and N-type semiconductors
– P: positive, N: negative

6. 6
Doping Process
• Adding impurities to silicon (Si)
dramatically changes electrical
behaviors of semiconductor.
– N-type: P, As
– P-type: B, Ga

7. 7
Diode Cross Section
• P-N junction
– P-type & N-type doped semiconductor
• Carrier: electron (-), hole (+)

8. 8
Forward & Reverse Bias
• Bias: DC voltage to set up a device
forward bias
reverse bias

9. 9
Depletion Region
• Insulating region within a doped
semiconductor material

10. 10
Basic Circuit
mA
k
R
V
I R
R
10
1
010





 
10100 
 RIV RR
forward bias reverse bias
0DV 0DI
• Ideal diode approximation

11. 11
Rectifier
• Ideal diode approximation
Output Waveform
Equivalent Circuits
Waveform of VD

12. 12
• Ohmmeter
– Real case: ideal diode mode is not suitable.
R Measurement
OL: Open Line
forward reverse

13. 13
V Measurement
• Voltmeter
– Cut-in voltage: almost 0.7 [V]
forward

14. 14
LED
• Light-Emitting Diode
• Various colors: R, G, B, W

15. 15
GaN Blue Diode
• Nagoya University & Nichia Corporation