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Type: Posts; User: htg
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23rd August 2019, 19:44
 Replies
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 297
Closed: Transition frequency fT of a transistor  definition
Is it the frequency at which power gain decreases by 3dB or frequency at which gain drops to unity? Does current gain count here or power gain?

21st August 2019, 12:53
Thread: Did early power MOSFETs have body diode?
by htg Replies
 1
 Views
 224
Closed: Did early power MOSFETs have body diode?
Also I would like to know if smallsignal MOSFETs have body diode.

12th August 2019, 02:29
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Closed: Re: Cutoff current through an Nchannel power MOSFET with negatively charged gate
In the response of dick freebird above there is the statement:
"GIDL (gate induced drain leakage) is a thing in some types
of MOSFETs (though I've seen it more in integrated, plain
FETs). That... 
11th August 2019, 21:15
 Replies
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 366
Closed: Re: Cutoff current through an Nchannel power MOSFET with negatively charged gate
I am clearly asking about MOSFETs, so gate current should be much smaller than drain current.

11th August 2019, 17:21
Thread: Optimally Accurate 28bit A/D conversion
by htg Replies
 8
 Views
 496
Closed: Re: Optimally Accurate 28bit A/D conversion
New production techniques may be necessary  e.g. all Cu ICs including leads, microwelding. For a given A/D converter it is possible to compensate for nonlinearity.

11th August 2019, 16:23
Thread: Optimally Accurate 28bit A/D conversion
by htg Replies
 8
 Views
 496
Closed: Re: Optimally Accurate 28bit A/D conversion
What is the fastest 28bit A/D converter?

11th August 2019, 16:03
Thread: Optimally Accurate 28bit A/D conversion
by htg Replies
 8
 Views
 496
Closed: Optimally Accurate 28bit A/D conversion
If I want e.g. 28bit accurate A/D conversion by multiple conversions and averaging, what is the optimal A/D converter  so that total conversion time is the shortest?

11th August 2019, 12:13
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 366
Closed: Cutoff current through an Nchannel power MOSFET with negatively charged gate
How low can such current be?

5th August 2019, 17:15
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 522
Closed: Are there really ferrites for multiGHz frequencies?
Supposedly Hexaferrite (barium ferrite) works at such frequencies. But I have found information that it has permeability = 1.1, so it is not much gently speaking. If there are such highfrequency...

5th August 2019, 17:09
 Replies
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 522
Closed: Where Can I buy Transformer Core Ferrites for Frequencies ABOVE 200 MHz ?
I know of 200 MHz ferrites e.g. by National Magnetics Group. Are there any ferrites good for transformers above 200 MHz?

9th December 2018, 13:40
Thread: Permittivity of Ferrites
by htg Replies
 2
 Views
 920
Closed: Permittivity of Ferrites
Various sources give different information regarding permittivity of ferrites.
They seem to agree that epsr = 10 to 20 for NiZn ferrites, but for MnZn ferrites they quote values from 10 to 300.
I... 
8th December 2018, 21:38
Thread: Hysteresis material constant
by htg Replies
 0
 Views
 307
Closed: Hysteresis material constant
I would like to know what values of nB I can expect for NiZn ferrites and for MnZn ferrites (*10^6/mT). Also, I want to know what B value I should use in the equation tan(delta) = nB*mur*B  should...

16th June 2018, 23:00
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Closed: What if the skin depth is of the order of 100 pm?
If the skin depth is subatomic, it seems that resistance will not increase when compared with the situation when skin depth = atomic diameter.

16th June 2018, 22:41
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 459
Closed: Re: Inductance of not very long stretch of litz wire
Imagine two metal balls at ends of the short stretch of litz wire. The balls are unipolar capacitors.
Will this system have approximately the same resonant frequency as a similar system made with... 
16th June 2018, 18:57
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 459
Closed: Inductance of not very long stretch of litz wire
Probably twisting increases inductance as compared to solid wire. I would like to know to what extent.

25th February 2018, 12:32
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Closed: Re: Electrodynamics, wave equation, velocity of waves
1) Photons do not exist at all. Look at lower and upper limits of frequency for photoelectric effect.
2) I am asking about phase velocity of a magnetically longitudinal, electrically torsional wave... 
24th February 2018, 15:47
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 5,877
Closed: Re: Electrodynamics, wave equation, velocity of waves
If you believe in photons, then you should look at the TRUE characteristics of photoelectric effect: it is a resonance phenomenon, it has lower and upper limit of frequency.

24th February 2018, 03:38
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[SOLVED]Closed: Telegrapher's equations  How can one obtain wave equations
How can we start from
dV/dx =  L dI/dt
and
dI/dx = C dV/dt
to obtain a pair of wave equations?
   Updated    
23rd February 2018, 23:53
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 5,877
Closed: Re: Maxwell's equations  is there a bigger picture?
I give clear examples where Maxwell's equations are violated.
Maxwell's equations are supposed to be valid in any situation which can
be encountered in Electrodynamics. There are no hidden... 
23rd February 2018, 19:12
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 5,877
Closed: Electrodynamics, wave equation, velocity of waves
1) div(B)=0 and div(E)=0 are true only in magnetostatic and electrostatic situations, otherwise they can be violated (consider a Gaussian beam of EM waves).
2) Maxwell's extension of the Ampere's... 
18th February 2018, 13:55
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Closed: 1 ns switching time power transistor  how can I find such?
I want to find a 10A, 100V, 1 ns switching time transistor. Google search only leads to much slower transistors.
Can you help me? 
13th February 2018, 17:49
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 5,877
Closed: Maxwell's equations  is there a bigger picture?
Maxwell's Equations sometimes are satisfied and sometimes are not satisfied. Examples:
1) Gauss' Law can be violated e.g. by a Gaussian beam of EM waves.
2) Ampere's law leads to the equation... 
7th February 2018, 19:32
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Closed: Maxwell's equations for a magnetically longitudinal wave
Consider a magnetically longitudinal nearfield wave in a ferrite rod.
Maxwell's equations lead to grad(div(B))  ΔB =  µ*ε*(d^2 B/dt^2).
This is not nontrivially satisfied e.g. by B(x,y,z,t) =... 
29th January 2018, 17:03
Thread: Violation of Gauss Law
by htg Replies
 5
 Views
 1,177
Closed: Re: Violation of Gauss Law
Polarization of the beam is vertical, so lines of E field will be in vertical planes.

29th January 2018, 16:36
Thread: Violation of Gauss Law
by htg Replies
 5
 Views
 1,177
Closed: Re: Violation of Gauss Law
Flux density will quickly decrease as we go up from the axis of the beam.
The side walls should be aligned with the lines of the E field so that the flux
through each of them is zero. Thanks to...
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