# Tag Info

14

The physical 'meaning' of the imaginary part of the impedance is that it represents the energy storage part of the circuit element. To see this, let the sinusoidal current $i = I\cos(\omega t)$ be the current through a series RL circuit. The voltage across the combination is $$v = Ri + L\frac{di}{dt} = RI\cos(\omega t) - \omega LI\sin(\omega t)$$ The ...

5

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 ...

5

There is a physical meaning behind the imaginary component of the impedance. You can re-cast the complex impedance $Z = R + jX$ (using engineering's notation $j$ for the imaginary unit) in polar form to get $Z = |Z|\exp(j\phi)$. $|Z|$ is the magnitude of the impedance, and scales the amplitude of the current to get the amptlitude of the voltage. $\phi = ... 4 From "The Transistor, A Semi-Conductor Triode", by J. Bardeen and W. H. Brattain, Phys Rev. 74(2), 230-231 (1948): "The device consists of three electrodes placed on a block of germanium as shown schematically in Fig. 1. Two, called the emitter and collector, are of the point-contact rectifier type and are placed in close proximity (separation ~0.005 to ... 3 Calling it a built-in voltage is something of a misnomer. People usually think of "voltage" as "what you measure with a voltmeter". So "voltage" is normally synonymous with "electrochemical potential of electrons" (in stat mech terminology) and with "difference in fermi level" (in semiconductor terminology). Under this definition, the built-in "voltage" is ... 3 The answer is that the whole circuit is full of electrons. I think you may be thinking along the lines of "if I switch a tap on, the water takes time$v/L$to reach the end of a hose of length$L$. So, if I switch a light on, the electrons must take analogous time the reach the light". Because the circuit is full of electrons, the energy source shoves the ... 3 The electrons need to get from the top to the bottom without any interference from any gas molecules that might be in the channels. If nothing else, collisions with gas molecules will degrade performance. At atmospheric pressure, I don't think the device would work at all. You can blow a hole through an MCP with over-voltage, but I'm not sure how this ... 2 The complete explanation takes a few lectures - it is simply impossible to provide this amount of information as an answer. Very general explanation: Let's take a look at NMOS transistor (the one shown in the schematic attached to the question). It has 4 pins which you can force potentials on: Gate Bulk Source Drain In order to understand how the ... 2 The light output of a LED is pretty linear with the current through it, over its normal operating range. Light does usually drop off from linear with current at the high end. Sometimes that high end is not included in the normal operating range, so the graph you see in the datasheet will be linear. Common T1-3/4 20 mA indicator LEDs are usually linear ... 2 The analogies may be built in various ways – similar simple mathematical relationships like$U=RI$are among many of them – but I would choose the analogy consistent with the Czech language where "napětí" [nuh-pyeh-tyea] means both "voltage" and "tension". I guess that even English speakers must sometimes say "electric tension" instead of "voltage". In the ... 2 Is it possible to produce gamma radiaton using radio emitter? Unlikely. A 'radio emitter' consists of, at least, some type of antenna and a transmitter to drive that antenna. The size of the antenna is related to the wavelength of the transmitted radio wave, e.g., half-wave dipole, quarter-wave monopole. But the wavelength of gamma rays is less than ... 2 A pn junction is one piece of a semiconductor that receives n-type doping in one section and p-type doping in an adjacent section. If you simply stick two p-type and n-type semiconductors to each other by hand, it will not behave as a diode. The main reason that a pn junction can behave as a one-directional device is it's built-in potential. Upon formation ... 2 One form of evidence is the ionization energies of silicon. Nth ionization energy is the energy needed to remove the nth electron. There is a big jump going from the 4th ionization energy (~4000 kJ/mol) to the 5th ionization energy (~16000 kJ/mol). Another form of evidence is the compounds silicon makes. Silicon forms$\mathrm{SiH}_4$,$\mathrm{SiF}_4$, ... 1 Another interesting analogy, pointed out by Prof. Graeme Milton, can be seen when you examine Maxwell's equations in media at a fixed frequency$\omega$:$$\boldsymbol{\nabla} \times \mathbf{E} = i\omega\boldsymbol{\mu}(\mathbf{x})\cdot\mathbf{H}(\mathbf{x}) ~;~~ \boldsymbol{\nabla} \times \mathbf{H} = ... 1 Radios work with a form of radiation called non-ionizing radiation. This means the EM waves contain enough energy to move the atoms (charges) around but not enough energy to break particles loose. Ionizing radiation removes particles because they carry a lot more energy and can break atomic bonds. These travel as UV-rays, x-rays or gamma-rays. In ... 1 In this case, the magnitude is telling you how to scale your input signal, and the argument is telling you how to phase shift it. Complex numbers usually represent 'amplification' and 'twist'. So, say, 1 means 'leave it the same', 2 means 'double it', 0.5 means 'halve it', i means 'one quarter turn', -1 means 'one half turn', -3i means 'triple it and give ... 1 Imaginary components in physics often mean phase shifts. In this case the impedance is sort of like a resistance, but it kicks in when there's a changing current by messing with its phase. 1 Earth's zero potential is just an arbitrary point similar to (0,0) of co-ordinate system. It has been chosen for Engineering practices because it has very very low theoretical potential (in light with charge at Infinity) and it's easily accessible to everyone and adding charge to it doesn't change it's theoretical potential. With reference to this arbitrary ... 1 Even if the floating Al film is (nearly) disconnected in DC, it is still capacitively coupled to the substrate. Since Kelvin probe techniques use capacitance modulation, the behaviour of the experiment will be more or less identical to the case of a connected film, since tip-film capacitance is so tiny compared to the film-substrate capacitance. It's ... 1 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 ... 1 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 ... 1 There are a few factors that govern laser diode turn-on time. The first is the junction capacitance, which is the same thing that causes turn-on delay in an ordinary junction diode. Under forward bias, the capacitance is proportional to the current and the diode transit time, just as with any pn-junction diode. The second is unique to laser diodes. ... 1 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 ... 1 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 ...

1

The ground which locates in the non-inverting terminal of an Op-Amp is called virtual ground.

1

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 ...

1

An exciton really is a electron coupled to a hole, just as you said. A electron gets excited to a higher band, leaving a hole in the lower band behind (a bit like a bubble on top of a liquid). You can disregard the other electrons (and holes) in this picture, as they are smeared out and just form the background. The electron and the hole are attracted to ...

1

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 ...

1

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). ...

Only top voted, non community-wiki answers of a minimum length are eligible