3. Series Connection Series Connection Requires more voltage The supply voltage should be the sum of the rated voltage required for LED

4. Parallel Connection Parallel Connection Requires more current The supply current should be the sum of the rated current requirement for LED

7. Each of the seven segment ( and the decimal point) in a given digit contains an individual LED.

8. When a suitable voltage is applied to a given segment LED, current flows through and illuminates that segment LED.

9. Application  Numeric display  Clocks  Calculators  Scoreboard

12. Infrared is light that has a range of wavelengths greater than the visible light.

13. Therefore, this LED can produce light but invisible light.

14. Application  TV remote control transmitter  Security system

17. Photo diode is a pn junction device that operates in reverse bias.

18. The photodiode has a small transparent window that allows light to strike the pn junction

19. Application  Receiver of the infrared LED

22. This diode maintain a constant current The current regulator diode operates in forward bias and the forward current becomes a specified constant value at forward voltage ranging from about 1.5V to about 6V

25. Used primarily in high- frequency and fast switching applications Formed by joining a doped semiconductor region with metal such as gold, silver, or platinum

28. Consist of heavily doped p and n regions separated by an intrinsic region When in reverse-bias, the pin diode acts like a nearly constant capacitance When forward-bias, it acts like a current-controlled variable resistance

29. Application  Used as a DC-controlled microwave switch operated by rapid changes in bias or as a modulating devise that takes advantage of the variable forward resistance characteristic  Used in attenuator applications because its resistance can be controlled by the amount of current  Used as photo detectors in fiber-optic system

32. Exhibits a special characteristics known as negative resistance This features makes it useful in oscillator and microwave amplifier application Constructed with germanium or gallium arsenide by doping the p and n regions much more heavily than in a conventional rectifier diode

35. LASER (Light Amplification by Stimulated Emission of Radiation) LASER light is monochromatic

36. Application  Pick up system of compact disk player  Printers and fiber communication