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Photo transistor always work with solar power
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∙ 11y ago
Ian Batty
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What are the characteristics of Diode transistor logic?
relatively large propagation delay.
What does transistor to transistor logic mean and what are its uses?
A: TTL-DTL-RTL are family of gates called by the name. Example TTL means Tran. trans. logic. It refers to the inputs for these gates as the type. T= Transistor D=Diode R=Resistor While they do perform the same function their characteristics in performance varies greatly.
Is active is a cutoff region of transistor?
The active region of a transistor is when the transistor has sufficient base current to turn the transistor on and for a larger current to flow from emitter to collector. This is the region where the transistor is on and fully operating.
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.
Different between power transistor and transistor that used in small signal?
Power transistor can conduct large amount of currents through it, more than small signal transistor. power transistor has a vertical structure and small signal transistor has horizontal structure.In power transistor quasi saturation region is present which is absent in the small signal transistor. In power transistor there is a inculsion of drift layer which is not there in the small signal transistor. Power dissipation is less in power transistor and it is more in small signal transistor. b.v.polytechnic,vasai pushkar vaity.
What is photo transistor?
Photo transistor always work with solar power
Is L14F a photo transistor?
yes
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
What is the disadvantage and advantage of photo diode and transistor?
photo diode donot work for long distance photo diode act as a receiver
What are the characteristics of Diode transistor logic?
relatively large propagation delay.
Does a CD-ROM use a audio sensor to read data?
No the sensor is an LED and a photo-transistor.
How a photo transistor works?
tda 4935 equilent ic IC TDA 4935 equilent
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.
How transistor work as a diode?
A: Actually a transistor have two diode with the base mas a common terminal. the characteristics of these tow diodes however are not the same as a common diode
How a NPN photo transistor works?
tda 4935 equilent ic IC TDA 4935 equilent
Inputoutput and transfer characteristics of pnp and npn transistor in common base configuration?
result of output characteristics of npn transister in CB mode
