Principles of Photodiode and Phototransistor
PHOTODIODE
* a type of photodetector capable of converting light into either current or voltage, depending upon the mode of operation. The common traditional solar cell used to generate electric solar power is a large area photodiode. * a semiconductor with a p-n junction
PRINCIPLES OF PHOTODIODE * Photons is the source of its energy * Energy can be solved by the equation: W=hf
Where:
h =Planck’s constant= 6.624×10-34 f = frequency * The frequency is, in turn, directly related to the wavelength (distance between successive peaks) of the traveling wave by the following equation:
= Vf
= wavelength f = frequency
V = velocity of light
* 1 lm=1.496×10-10 W * Light intensity is measured in lmft2, footcandle (fc), or Wm2 * The operation of the photodiode is limited to reverse bias region. * The application of light will result to the transfer of energy(photons) * Dark current - current that will exist without illumination.
APPLICATIONS
* employed in an alarm system. * reverse will continue to flow as long as the light beam does not broken * used to count items in the conveyor’s belt. * item passed the light beam then it will be broken the current will drops to the dark current level and the counter will increase.
PHOTOTRANSISTOR
* A photoelectric device with photosensitive collector-base p-n junction. The current induced by photoelectric effects is the base current of the transistor.
PRINCIPLES OF PHOTOTRANSISTOR
* If we assign the notation I , for the photoinduced base current, the resulting collector current, on an approximate basis is Ic≅hfe I * An increase in light corresponds with the increase in collector current.
APPLICATIONS
* Punch-card readers * Computer logic circuitry * Lighting control * Level indication * Relays * Counting systems * High isolation AND gate using three phototransistors and three LED as is
* a type of photodetector capable of converting light into either current or voltage, depending upon the mode of operation. The common traditional solar cell used to generate electric solar power is a large area photodiode. * a semiconductor with a p-n junction
PRINCIPLES OF PHOTODIODE * Photons is the source of its energy * Energy can be solved by the equation: W=hf
Where:
h =Planck’s constant= 6.624×10-34 f = frequency * The frequency is, in turn, directly related to the wavelength (distance between successive peaks) of the traveling wave by the following equation:
= Vf
= wavelength f = frequency
V = velocity of light
* 1 lm=1.496×10-10 W * Light intensity is measured in lmft2, footcandle (fc), or Wm2 * The operation of the photodiode is limited to reverse bias region. * The application of light will result to the transfer of energy(photons) * Dark current - current that will exist without illumination.
APPLICATIONS
* employed in an alarm system. * reverse will continue to flow as long as the light beam does not broken * used to count items in the conveyor’s belt. * item passed the light beam then it will be broken the current will drops to the dark current level and the counter will increase.
PHOTOTRANSISTOR
* A photoelectric device with photosensitive collector-base p-n junction. The current induced by photoelectric effects is the base current of the transistor.
PRINCIPLES OF PHOTOTRANSISTOR
* If we assign the notation I , for the photoinduced base current, the resulting collector current, on an approximate basis is Ic≅hfe I * An increase in light corresponds with the increase in collector current.
APPLICATIONS
* Punch-card readers * Computer logic circuitry * Lighting control * Level indication * Relays * Counting systems * High isolation AND gate using three phototransistors and three LED as is