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In-line amplifier

  1. Aug 20, 2015 #1
    Hello. I'm looking for the electrical schematics of this kind of in-line amplifier use behind LNB of Sat Tv to compensate coax loss. I'm mainly interested by a 2 transistor amplification chain. My request is to get idea for a personal realization totally out of tv application ...
  2. jcsd
  3. Aug 20, 2015 #2


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    Staff: Mentor

    Here is some good starting info on Low Noise Block downconverters: http://www.satsig.net/lnb/explanation-description-lnb.htm

    What frequency range do you want to cover with your in-line amplifier? What other specs can you share? Input and output powers, power supplies available, noise figure, etc. :smile:
  4. Aug 21, 2015 #3
    Thanks for reply. I really need a real schematics of a 2 stages in-line amp. My concern is about : how to connect DC power from output plug to input plug without risk of oscillation. I realized that and I'm unable to kill the oscillation (2 stages -> 180 ° ...)
  5. Aug 21, 2015 #4


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    Science Advisor

    The DC power is diverted through a LPF. The AC amplifier is designed as a HPF that when considered with the DC LPF has a total gain below unity.

    If you want a circuit diagram then you need to give a make and model number or specify the gain and bandwidth requirements of your application.
    What is the frequency band you need? How long is your coaxial cable, type number, and what is it's attenuation at what frequencies.
  6. Aug 22, 2015 #5


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    2017 Award

    Personally I wouldn't even use a one or 2 discrete transistor amplifier
    just too much messing around getting impedance matching correct.

    you would be much better off using a single MMIC amplifier

    here is one of several companies that make them
    datasheets with schematics are available for their devices ( free registration)


    googling will find other devices .... MMIC's make the job extremely easy .... I wouldn't consider any other way

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