Page 21 - Shellie Suzana Binti Saad
P. 21
PHOTO TRANSISTOR
(OPERATIONAL CIRCUIT)
Two basic modes of operation
Active mode
The phototransistor generates an output
response based on the light or irradiance
level.
It provides a response that is very broadly
proportional to the light stimulus.
Switch mode
They are widely used because of the non-
linear response of the Photo Transistor to
light.
When there is little or no light, no current
will flow in the transistor, and it will be in
the off state.
However as the level of light increases,
current starts to flow.
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