# Tag Info

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You might find the Yahoo "home_transistor" group a useful resource. There's also a series of videos on YouTube by Jeri Ellsworth including some where she makes transistors. In one, in particular, she takes the crystal out of a germanium point-contact diode and turns the crystal into a point-contact transistor (much like the Bell Labs transistor.) There ...

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In experimental physics it is required to use electronics as instruments. You must know how they work(amplifiers, ADC's, MCA's etc) in order to fully understand and design an experiment. Usually, you don't need too much electronics(filters, amplifiers, transistors, digital electronics-boolean algebra) is more often than not, more than enough. You need ...

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The key difference between a Zener diode and a normal diode is that the Zener diode has a low breakdown voltage - typically in the few volts range. The breakdown voltage is low because the heavy doping means the depletion layer is very thin, and even at a low voltage the field strength over this thin depletion layer is very high. With a conventional diode ...

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From "The Transistor, A Semi-Conductor Triode", by J. Bardeen and W. H. Brattain, Phys Rev. 74(2), 230-231 (1948): "The device consists of three electrodes placed on a block of germanium as shown schematically in Fig. 1. Two, called the emitter and collector, are of the point-contact rectifier type and are placed in close proximity (separation ~0.005 to ...

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Calling it a built-in voltage is something of a misnomer. People usually think of "voltage" as "what you measure with a voltmeter". So "voltage" is normally synonymous with "electrochemical potential of electrons" (in stat mech terminology) and with "difference in fermi level" (in semiconductor terminology). Under this definition, the built-in "voltage" is ...

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The answer is that the whole circuit is full of electrons. I think you may be thinking along the lines of "if I switch a tap on, the water takes time $v/L$ to reach the end of a hose of length $L$. So, if I switch a light on, the electrons must take analogous time the reach the light". Because the circuit is full of electrons, the energy source shoves the ...

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For a given circuit in a given technology, power increases at a rate proportional to $f^3$ or worse. You can see by looking at the graph in @Martin Thompson's answer that power is superlinear in frequency. $P=c V^2 f + P_S$ is correct, but only superficially so because $f$ and $P_S$ are functions of $V$ and $V_{th}$ (the threshold voltage.) In practice ...

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The complete explanation takes a few lectures - it is simply impossible to provide this amount of information as an answer. Very general explanation: Let's take a look at NMOS transistor (the one shown in the schematic attached to the question). It has 4 pins which you can force potentials on: Gate Bulk Source Drain In order to understand how the ...

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A pn junction is one piece of a semiconductor that receives n-type doping in one section and p-type doping in an adjacent section. If you simply stick two p-type and n-type semiconductors to each other by hand, it will not behave as a diode. The main reason that a pn junction can behave as a one-directional device is it's built-in potential. Upon formation ...

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The fundamental reason for this is that light is quantized. If it wasn't for this, it would in theory be possible to scale down any camera to an arbitraily small size. However, as a camera is scaled down, less light will enter it and therefore fewer photons. As the number of photons hitting a pixel goes down, the shot noise goes up (the signal-to-noise-ratio ...

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The light output of a LED is pretty linear with the current through it, over its normal operating range. Light does usually drop off from linear with current at the high end. Sometimes that high end is not included in the normal operating range, so the graph you see in the datasheet will be linear. Common T1-3/4 20 mA indicator LEDs are usually linear ...

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The analogies may be built in various ways – similar simple mathematical relationships like $U=RI$ are among many of them – but I would choose the analogy consistent with the Czech language where "napětí" [nuh-pyeh-tyea] means both "voltage" and "tension". I guess that even English speakers must sometimes say "electric tension" instead of "voltage". In the ...

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I have a couple courses in the atomic nature of analog and digital electronics next year. I'm in Engineering Physics, so I'm not exactly sure which side that confirms, though the courses are in the physics department. Eng Phys has its own courses as well, so if the physics department has these courses then I assume physics majors also have some use for ...

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In the first chapter of Sze's classic Physics of Semiconductor Devices, one can find: (1) in low electric fields, the drift velocity of carriers is proportional to the electric field strength (section 1.5 in the 2nd edition). It then gives a number of approximations, depending on the primary scattering mechanism. (2) in high field regions, nonlinearities ...

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Optical systems not involving magnetic fields are symmetric. So, if the display passes light in one direction, it will pass light in the other. Putting a mirror at the back of the TFT and lighting it from the front is therefore equivalent, expect that some light will be attenuated on the way in as pointed out by @CarlWitthoft in the comments. As a ...

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First of all note, that ions do not move in the semiconductor. Only electrons and holes move there. The depletion results from diffusion of the free electrons from the n-region into the p-region and the diffusion of holes from the p-region into the n-region. In either case it is a thermodynamical process. The electrons form something like a dense gas in ...

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The voltage across a capacitor cannot change when there is no current, so if there is no current, as the input voltage rises, the output voltage also rises. There is no current (or almost no current) when the voltage across that diode is positive. According to Wikipedia there are better ways to make voltage doublers.

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Background (Taken from Millman's book) An ideal p-n diode has zero ohmic voltage drop across the body of the crystal. We assume that the external bias voltage appears directly across the junction.To justify this assumption we must specify how electric contact is made to the semiconductor from the external bias circuit.we indicate metal contacts with which ...

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This diagram (cribbed from here) shows the voltage current curve for a typical zener diode: Below the breakdown voltage the diode does not behave as a perfect insulator, but has a small leakage current. This means the voltage across the diode is strongly current dependant. The minimum current, $I_{Z(mini)}$, is simply the current at which the breakdown is ...

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Two points: the drift velocity is the average velocity of electrons. The actual speed of electrons in a metal is quite large, however they go in every direction so the current is zero in the absence of an applied field. An applied electric field will cause slightly more electrons to go one way than the other resulting in a small average drift velocity. The ...

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There are actually several different things going on. The reason you hear a single tone is because of resonance. The reason that it is usually a higher frequency tone has to do partly with the falloff in amplification with distance and partly (perhaps mainly) with the frequency response of the microphone/amplifier/loudspeaker. Let's model the situation ...

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I believe that the authors, of the reference you provided, explain the reason behind introducing these so-called quasi-Fermi levels at the end of section 4.3.3. For simplicity, let me just repeat it here; perhaps explaining it in different words, with a little more elaboration, would help. I’m sure you're aware of the fact that in $n$- ($p$-) doped ...

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After reading the wikipedia page and this article, I understand your question a little better. A CMOS sensor detects colors by letting light pass through three layers of detector, each with a certain spectral response and absorption. I don't think that each layer is specifically red, blue, and green, rather that their responses overlap and that the processor ...

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Usually, the Bulk of an NMOS is connected to the lowest voltage in the circuit, for an NMOS and the highest voltage in the circuit, for a PMOS. Then, depending on the value of this voltage and the Source-to-Bulk voltage of this transistor, a Threshold Voltage is defined, which is also called Turn On Voltage in some cases(especially in the digital circuits). ...

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I do believe that yes. The most hard part will be to obtain the materials. If you manage to get a good piece of n-type (or p-type) Silicon, big enough to allow you to work with home tools, you'll "just" have to do local oxidation (with temperature for example) and make some soldering. Of course, the quality of that transistor would be very doubtful as it ...

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Since you mention batteries in a comment: The voltage source + resistance model works well in many circumstances. At the extremes: high frequency / fast rise time waveforms: There will always be some inductance, from wiring if nothing else, which appears as an inductance, an easy add to the model. low frequency / long durations: As the battery ...

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There are actually two slightly different versions of Thevenin's theorem. I think what you are describing is the weaker of the two: you can replace any circuit with a single voltage/current source and a single resistor. That version holds for any two-terminal network made up only of voltage/current sources and ohmic resistors. It fails as soon as you add ...

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Reverse Bias of P-N junction When the voltage is applied this way round it tends to pull the free electrons and holes apart, and increases the height of the energy barrier between the two sides of the diode. As a result it is almost impossible for any electrons or holes to cross the depletion zone and the diode current produced is virtually zero. A few lucky ...

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Well, seems that Intel can often find some material to get closer to the physical limit. But the limit can't be reached, your transistor needs at least 1 atom. Another limit is on the clock frequency, which is essentially due to material's intrinsic property (mobility, or speed of electrons). Graphene may have a good chance for its ultrahigh mobility. One ...

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