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What is the emitter base collector in 2N5777 photo transistors?
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∙ 10y ago
1st pin is emitter then collector and base
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∙ 10y ago
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What is a phototransistor?
There is a wide selection of photosensitive devices that are available to the electronic designer. Whilst photo-diodes fulfil many requirements, phototransistors or photo transistors are also available, and are more suitable in some applications. Providing high levels of gain, and standard devices are low cost, these phototransistors can be used in many applications.The idea of the photo transistor has been known for many years. William Shockley first proposed the idea in 1951, not long after the ordinary transistor had been discovered. It was then only two years before the photo transistor was demonstrated. Since then phototransistors have been used in a variety of applications, and their development has continued ever since.Phototransistor structureAlthough ordinary transistors exhibit the photosensitive effects if they are exposed to light, the structure of the phototransistor is specifically optimised for photo applications. The photo transistor has much larger base and collector areas than would be used for a normal transistor. These devices were generally made using diffusion or ion implantation. Homojunction planar phototransistor structureEarly photo transistors used germanium or silicon throughout the device giving a homo-junction structure. The more modern phototransistors use type III-V materials such as gallium arsenide and the like. Heterostructures that use different materials either side of the p-n junction are also popular because they provide a high conversion efficiency. These are generally fabricated using epitaxial growth of materials that have matching lattice structures. These photo transistors generally use a mesa structure. Sometimes a Schottky (metal semiconductor) junction can be used for the collector within a phototransistor, although this practice is less common these days because other structures offer better levels of performance.Heterojunction mesa-structure phototransistorIn order to ensure the optimum conversion and hence sensitivity, the emitter contact is often offset within the phototransistor structure. This ensures that the maximum amount of light reaches the active region within the phototransistor.Phototransistor operationPhoto transistors are operated in their active regime, although the base connection is left open circuit or disconnected because it is not required. The base of the photo transistor would only be used to bias the transistor so that additional collector current was flowing and this would mask any current flowing as a result of the photo-action. For operation the bias conditions are quite simple. The collector of an n-p-n transistor is made positive with respect to the emitter or negative for a p-n-p transistor. The light enters the base region of the phototransistor where it causes hole electron pairs to be generated. This mainly occurs in the reverse biased base-collector junction. The hole-electron pairs move under the influence of the electric field and provide the base current, causing electrons to be injected into the emitter.Phototransistor characteristicsAs already mentioned the photo transistor has a high level of gain resulting from the transistor action. For homo-structures, i.e. ones using the same material throughout the device, this may be of the order of about 50 up to a few hundred. However for the hetero-structure devices, the levels of gain may rise to ten thousand. Despite their high level of gain the hetero-structure devices are not widely used because they are considerably more costly to manufacture. A further advantage of all phototransistors when compared to the avalanche photodiode, another device that offers gain, is that the phototransistor has a much lower level of noise. One of the main disadvantages of the phototransistor is the fact that it does not have a particularly good high frequency response. This arises from the large capacitance associated with the base-collector junction. This junction is designed to be relatively large to enable it to pick up sufficient quantities of light. For a typical homo-structure device the bandwidth may be limited to about 250 kHz. Hetero-junction devices have a much higher limit and some can be operated at frequencies as high as 1 GHz.The characteristics of the photo-transistor under different light intensities. They are very similar to the characteristics of a conventional bipolar transistor, but with the different levels of base current replaced by the different levels of light intensity.There is a small amount of current that flows in the photo transistor even when no light is present. This is called the dark current, and represents the small number of carriers that are injected into the emitter. Like the photo-generated carriers this is also subject to the amplification by the transistor action.
Why is biasing needed?
The function of BiasingA BJT (Bipolar Junction Transistor) require a voltage normally in the range of 0.7V for the internal junctions to become conductive. It is a fixed parameter of Silicon (Si) due to the amount of 1.1eV required to get electrons from the valence energy band into a conductive band. To be able jump the energy gap which is a forbidden band for electrons or to raise the Fermi energy level in the atom. The energy, whether it is electrically applied, thermally or optically, is required to be able change the state of a semiconductor from an insulator to an conductor. You can read more on "semiconductor theory" for better understanding. Then with a non-linear relationship the conductivity will increase as one increase the forward bias current through the base to emitter junction. Biasing is used for classical transistor amplifier applications. Biasing is required to have the transistor half way saturated for Class-A amplification or barely switched on for Class-B power amplifiers. If a Class-B amplifier is not biased, then the lower 0.7V of the audio or sine wave will not be amplified causing crossover distortion. When you bias it correctly, the distortions will be gone, since the entire half wave will then fit into the on state of the transistor. If a Class-A amplifier is not correctly biased, premature clipping on the positive or negative part of the wave will occur.Biasing may be used for other applications as well, such as photo transistors, internal construction of IC's such as op-amps.
What is photo transistor characteristics?
Photo transistor always work with solar power
What is photo detector?
A photo detector is a sensor of light or other electromagnetic energy. See the link below for more info.
What is the working principle of photoelectric transducer?
photo electric transducer
Is the 2N5777 photo diode an APD or a pin diode?
The 2N5777 is a Darlington silicon NPN photo detector, or, if you prefer a photoDarlington. A link is provided to a bit of data on this device.
How do you bias a 2N5777 photo transistor?
connect the base of the transistor to a variable resistor and to a normal resistor
How do you bias a 2N5777 photo-transistor?
connect the base of the transistor to a variable resistor and to a normal resistor
DHPT in full and how it works?
DHPT in full is Double Heterostructure Photo Transistor. DHPT works by interchanging the double heterostructure's emitter and collector all through when the transistor is in use.
Where can one purchase a photo transistor?
Photo transistors can be purchased at Radio Shack and Best Buy. Someone can also buy them online at Amazon, Newark/Element 14, and Mouser Electronics.
What kind of particles does the emitter create in a smoke alarm?
Smoke alarms typically use photo-electric sensors or alpha-particle emitters, although the photo-electric sensors are much better for detecting smoldering fires.
How does a semiconductor work?
we know that in a transistor we have three types of regions: EMITTER, COLLECTOR, BASE, and we know that emitter is highly doped, so charge carriers are very high, so resistance is very less, and on the other side collector is moderately doped so charge carriers are less, so resistance is very high. So from the above concept we conclude that in a transistor current is flowing from low resistance to high resistance. for example the 100 electrons are moving from emitter to base, in base only some (4 electrons) of the electrons are neutralized, and remaining 96 electrons are moved to collector terminal through high resistance path. so now same current flowing through high resistance so voltage amplified.
Why the compound semiconductors are not suitable for making transistors and ICs?
Compound semiconductors have very low lifetime of charge carriers and hence they are not used for making Transistors and ICs.Rather it is used for making LEDs and LASER diodes.So the compound semiconductors are called photo-diodes. -M.R
What is self bias common collector?
The picture quality is not that great but here is a drawing of a self biased common collector BJT http://imageshack.us/photo/my-images/200/selfbiasedcommoncollect.png/
What is a phototransistor?
There is a wide selection of photosensitive devices that are available to the electronic designer. Whilst photo-diodes fulfil many requirements, phototransistors or photo transistors are also available, and are more suitable in some applications. Providing high levels of gain, and standard devices are low cost, these phototransistors can be used in many applications.The idea of the photo transistor has been known for many years. William Shockley first proposed the idea in 1951, not long after the ordinary transistor had been discovered. It was then only two years before the photo transistor was demonstrated. Since then phototransistors have been used in a variety of applications, and their development has continued ever since.Phototransistor structureAlthough ordinary transistors exhibit the photosensitive effects if they are exposed to light, the structure of the phototransistor is specifically optimised for photo applications. The photo transistor has much larger base and collector areas than would be used for a normal transistor. These devices were generally made using diffusion or ion implantation. Homojunction planar phototransistor structureEarly photo transistors used germanium or silicon throughout the device giving a homo-junction structure. The more modern phototransistors use type III-V materials such as gallium arsenide and the like. Heterostructures that use different materials either side of the p-n junction are also popular because they provide a high conversion efficiency. These are generally fabricated using epitaxial growth of materials that have matching lattice structures. These photo transistors generally use a mesa structure. Sometimes a Schottky (metal semiconductor) junction can be used for the collector within a phototransistor, although this practice is less common these days because other structures offer better levels of performance.Heterojunction mesa-structure phototransistorIn order to ensure the optimum conversion and hence sensitivity, the emitter contact is often offset within the phototransistor structure. This ensures that the maximum amount of light reaches the active region within the phototransistor.Phototransistor operationPhoto transistors are operated in their active regime, although the base connection is left open circuit or disconnected because it is not required. The base of the photo transistor would only be used to bias the transistor so that additional collector current was flowing and this would mask any current flowing as a result of the photo-action. For operation the bias conditions are quite simple. The collector of an n-p-n transistor is made positive with respect to the emitter or negative for a p-n-p transistor. The light enters the base region of the phototransistor where it causes hole electron pairs to be generated. This mainly occurs in the reverse biased base-collector junction. The hole-electron pairs move under the influence of the electric field and provide the base current, causing electrons to be injected into the emitter.Phototransistor characteristicsAs already mentioned the photo transistor has a high level of gain resulting from the transistor action. For homo-structures, i.e. ones using the same material throughout the device, this may be of the order of about 50 up to a few hundred. However for the hetero-structure devices, the levels of gain may rise to ten thousand. Despite their high level of gain the hetero-structure devices are not widely used because they are considerably more costly to manufacture. A further advantage of all phototransistors when compared to the avalanche photodiode, another device that offers gain, is that the phototransistor has a much lower level of noise. One of the main disadvantages of the phototransistor is the fact that it does not have a particularly good high frequency response. This arises from the large capacitance associated with the base-collector junction. This junction is designed to be relatively large to enable it to pick up sufficient quantities of light. For a typical homo-structure device the bandwidth may be limited to about 250 kHz. Hetero-junction devices have a much higher limit and some can be operated at frequencies as high as 1 GHz.The characteristics of the photo-transistor under different light intensities. They are very similar to the characteristics of a conventional bipolar transistor, but with the different levels of base current replaced by the different levels of light intensity.There is a small amount of current that flows in the photo transistor even when no light is present. This is called the dark current, and represents the small number of carriers that are injected into the emitter. Like the photo-generated carriers this is also subject to the amplification by the transistor action.
Can you see transistors?
Basically, in transistor, the signal is transferred from low resistance circuit to the high resistance circuit. So it is called transfer+resistor=Transistor.Transistors are widely used in different types of switching, amplifiers, oscillators and integrated circuits.Based on the applications, the types of the transistors are as given below:General purpose transistors, Low frequency transistors, High frequency transistors, Power transistors, Switching transistors, Field Effect Transistors, MOSFET, Uni-junction Transistors, Bi junction transistors, Photo transistor, High power transistors, Complementary pair, Darlington amplifier, Video and R.F. amplifier, Ultrahigh frequency and microwave, Insulated gate bipolar transistors, Static induction transistors.More their to know about transistors are as given below:History of invention, Time-line throughout, Basic construction, Bias arrangement, working, Various currents in transistors, Basic transistor amplifier, Configurations, Characteristics, Current gain and relation among them, D.C. load line, Operating point, Biasing of transistor, stability factor, specifications and ratings, testing, colour coding, identification of transistor using multimeter, h-parameter of transistor, particular applications etc...
Can be a phototransistor be used for saving electric energy?
A photo transistor is a gate which is sensitive to light. Therefore it can be used in any circumstances where a circuit needs to be sensitive to light. Circuits which employ photo transistors and their relatives the photo-resistor and photo-diodes, are already used in such equipment as light switching. These circuits determine if it is dark enough to turn on street and domestic lights and turn them on or off when a preset level of light is present.
