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Attenuator impedance

Discussion in 'Electronic Basics' started by Deniz, Nov 20, 2004.

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  1. Deniz

    Deniz Guest

    We have this setting:

    ...--(56ohm)----(47ohm)----(47ohm)----(RG58/U to spectrum analyzer)
    | |
    (3.3ohm) |
    | ---
    ---

    47ohm, 47ohm and grounded 3.3ohm resistors form the three resistor
    attenuator.
    Attenuator attenuates the circuit output delivered to 56ohm load. Now
    what is the output impedance of attenuator?? and why? (asuming that
    RG58/U coaxial cable has an impedance of 50ohm)
     
  2. Is the 3.3 to ground between the two 47 ohm resistors or the 56 and
    the first 47 ohm resistors?

    Tom
     
  3. Spajky

    Spajky Guest

    this is a -36dB attenuator (T-type) schematics (with a Z transforming
    2:1 too) with approx. 50 ohm output impedance. (& normally approx. 100
    ohm input Z ). Since imedance of spectrum Anal. is 50 ohm & has
    connected the last R of 47 ohm in series, its input gets -6dB signal
    (half voltage of it= matching impedance) compared to the taken point
    on 3,3 ohm resistor (-30dB); so on the Analizer you get of TL -36dB
    attenuated signal (approx. only of 1/64 part of the voltage of main
    input signal with 50ohm matched inpedance /Z/ with Spec.Anal.) ...
     
  4. Deniz

    Deniz Guest

    Is the 3.3 to ground between the two 47 ohm resistors or the 56 and
    yes, 3.3 goes to ground btw the two 47 ohm resistors.
     
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