BPW77NB

Series:	--
Packaging:	Bulk
Part Status:	Active
Voltage - Collector Emitter Breakdown (Max):	70V
Current - Collector (Ic) (Max):	50mA
Current - Dark (Id) (Max):	100nA
Wavelength:	850nm
Viewing Angle:	20°
Power - Max:	250mW
Mounting Type:	Through Hole
Orientation:	Top View
Operating Temperature:	-40°C ~ 125°C (TA)
Package / Case:	TO-206AA, TO-18-3 Metal Can

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Optical Sensors - PhototransistorsThe BPW77NB is an optically responsive transistor used in sensing applications such as cameras and DVD readers. It is one of the most commonly used phototransistors. In this article, we will be discussing the applications of the BPW77NB as well as its working principle.ApplicationsThe BPW77NB is designed to detect light, responding directly to the intensity of light. As a result, it has many applications in sensing and automation that benefit from a variable optical response. For example, the BPW77NB is used in digital and analog cameras to control the exposure time. It is also used in DVD readers to detect the presence of a DVD, and in medical equipment, such as endoscopes, to detect the presence of tissue. Additionally, it is used in photocopy machines to detect the presence of paper.Beyond its imaging use, the BPW77NB is also useful for controlling industrial and home appliance motors. This is because it can detect when an object is in the field of view, allowing the device to activate for interaction with it. In this way, the BPW77NB can be used to drive automated machines and home appliances. Another application is in barcode readers, where the BPW77NB can be used to detect the white spaces between the black lines of a barcode.The BPW77NB is also a popular choice for automated lighting applications. It can be used in streetlights to turn them on when there is a decrease in light levels and for indoor applications, such as automatically turning lights on and off in response to the occurrence or absence of human occupancy.The BPW77NB is also suitable for detecting the presence of smoke, water, or gas. This is because it is able to detect changes in the amount of light traveling through the intervening gas or liquid medium. In this way, the BPW77NB can be used in smoke detectors, water-level sensors, and gas detectors.Working PrincipleThe BPW77NB is a type of phototransistor, a three-terminal device that functions as an electronic switch and amplifier, and it reacts to the intensity of light.At the most basic level, a phototransistor is composed of two semiconductor layers. In the case of the BPW77NB, it is composed of an n-type semiconductor and a p-type semiconductor. The n-type layer contains many free electrons, while the p-type layer contains many “holes” (i.e., missing electrons). These two layers are in contact with each other, forming an internal junction called the base-collector junction. When a light signal is incident onto this junction, it causes some of the semiconductor valence electrons to move into the conduction band, creating a current. The current is then amplified by the collector of the transistor.In operation, the BPW77NB has two terminals connected to it: the base and the collector. The base is connected to the light signal source, while the other terminal is connected to an output device (such as a motor). When the light signal is incident onto the base-collector junction, the amount of current flowing through the transistor depends on the intensity of the incident light signal. Thus, by varying the intensity of the light signal, the current passing through the BPW77NB can also be changed. This allows for the input light signal to be converted into an adjustable output current.ConclusionThe BPW77NB is a versatile phototransistor that is used in a variety of applications. It is used in cameras, DVD readers, medical equipment, photocopiers, barcode readers, and home appliances. It is also used in lighting and gas detection applications. Its working principle is simple; the passage of a current through the phototransistor is dependent on the intensity of light incident on the base-collector junction. Thus, by adjusting the light signal, the BPW77NB can be used to convert light into a controlled output current.

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