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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?

    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?
  3. 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?
  4. 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...
  5. 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?
  6. 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?
  7. H

    Did early power MOSFETs have body diode?

    Also I would like to know if small-signal MOSFETs have body diode.
  8. 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?
  9. H

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

    How low can such current be?
  10. 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?
  11. 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.
  12. 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 ?
  13. 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.
  14. H

    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.
  15. H

    [SOLVED] 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 - - - Start by calculating d^2 V/dx^2 and d^I/dx^2, substitute RHS of the original equations for dV/dx and for dI/dx and you get it.
  16. H

    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?
  17. H

    Electrodynamics, wave equation, velocity of waves

    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 grad(div(B)) - Δ (B) = -mu0*eps0*(d^2 B/dt^2) which...
  18. H

    Violation of Gauss Law

    Consider a horizontally propagating Gaussian beam of EM waves of vertical polarization. Consider a box with rectangular horizontal top and bottom, and with side walls going in the direction of the electric field E. Let the box be above the axis of the Gaussian beam. If the box is tall enough...
  19. H

    Maxwell's equations for a magnetically longitudinal wave

    Speed of a longitudinal magnetic wave in ferrite If I wind a short coil on a ferrite rod and run AC through it, then a wave will go through the ferrite rod. This wave is magnetically longitudinal and electrically torsional. My question is: is the speed of such a wave equal to c/SQRT(εr*µr) ?
  20. H

    Principle of Linear Superposition vs Law of Conservation of Energy

    EM wave propagating from an antenna should have the E field proportional to 1/r according to the Law of Conservation of Energy, but according to the Linear Superposition Principle E should be proportional to 1/r^2. Does anybody have EXPERIMENTAL DATA?

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