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  1. H

    Rise times and fall times of fast transistors seem way too long

    In the data sheet of a 400 MHz transistor I found fall time = 60 ns. Clearly these are contradictory specifications - trise and tfall should be at least an order of magnitude shorter. Should I believe that fT is specified correctly? (e.g. 2SA2088FRAT106Q transistor).
  2. H

    Precision op amps - is 1 microvolt offset believable?

    Chopper amplifier of microvolt DC signals I understand that a chopper keeps flipping the input DC signal so that an AC signal is obtained and amplified. But to do it with microvolt signals requires using noise-free switches. The only relatively noise-free method of switching that comes to my...
  3. H

    Precision op amps - is 1 microvolt offset believable?

    I saw it in a data sheet of an Analog Devices MOSFET-input precision op amp. Has anyone tried to use such an op amp, so you can tell me if 1 µV voltage offset is true?
  4. H

    Communication with geostationary satellites (~ 36 000 km distance)

    Is there direct communication with satellites which are so distant from us? What power levels are used by their transmitters?
  5. H

    The truth about coaxial cables at high frequencies

    With the specific inductance of the order of 1 microHenry/m and specific capacitance 100 pF/m it is hard to believe low attenuation at GHz range. To get a brutal estimate, consider length = 1m and ω = 6 Grad/s - then we are dealing with 6kΩ of inductive reactance and with 1.66 Ω of capacitive...
  6. H

    The truth about coaxial cables at high frequencies

    High inductive impedance and low capacitive impedance of coaxial cables make it unbelievable that with proper resistive termination R such a coaxial cable behaves like a lossless line with the resistance R at the end. Do HF probes in oscilloscopes brutally amplify signals to make up for...
  7. H

    Seeing a crisp rectangular wave on an oscilloscope

    There do not seem to be good probes on the market. I want to see a 5 MHz rectangular wave with 500 ps switching time. Is anyone aware of a solution of this problem?
  8. H

    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?
  9. H

    Did early power MOSFETs have body diode?

    Also I would like to know if small-signal MOSFETs have body diode.
  10. H

    Cut-off current through an N-channel 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 means after some distance into negative Vgs, drain current increases from its minimum." My original...
  11. H

    Cut-off current through an N-channel power MOSFET with negatively charged gate

    I am clearly asking about MOSFETs, so gate current should be much smaller than drain current.
  12. H

    Optimally Accurate 28-bit 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.
  13. H

    Optimally Accurate 28-bit A/D conversion

    What is the fastest 28-bit A/D converter?
  14. H

    Optimally Accurate 28-bit A/D conversion

    If I want e.g. 28-bit accurate A/D conversion by multiple conversions and averaging, what is the optimal A/D converter - so that total conversion time is the shortest?
  15. H

    Cut-off current through an N-channel power MOSFET with negatively charged gate

    How low can such current be?
  16. H

    Are there really ferrites for multi-GHz 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 high-frequency ferrites with decent permeabilities, where can I buy them?
  17. H

    Are there really ferrites for multi-GHz frequencies?

    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?
  18. H

    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 would like to know velocity of EM waves in ferrites, so knowing epsr would help.
  19. H

    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 it be the B value achieved in the magnetic for a given application or Bsaturation ?
  20. H

    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.

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