HDTV Amplfication Project

Discussion in 'Homework Help' started by dhice, Apr 13, 2008.

  1. dhice

    Thread Starter New Member

    Apr 13, 2008
    Hi all, first post, and before I begin, thank you in advance for any help given. First I'll post the project parameters:

    He also references an example circuit http://www.electronics-lab.com/projects/rf/003

    After a bit of investigation I learned that HDTV frequencies will be using mostly the same frequencies and channels of the current television stations. I did read somewhere that channels 8-13 are capable of using HDTV signals due to the higher frequencies than that of the other VHF signals.

    So the design I have came up with, has been:

    Input->High Band Filter -> Common-Emitter Amp -> Low Band Filter

    I put the filters in the design so it would not amplify lower signals such as FM radio, and higher signals such as wireless phones.

    The hard part has been to find a suitable transistor that will provide enough gain from the frequencies from at least 177 MHz to 879 MHz. I have tried several different transistors but none of them seem to cover the entire spectrum of my band.

    I seem to have gotten the filters setup correctly, but when I was building the amplifier the best circuit I could come up with (attached via multisim circuit file) was an amp that had a .8 gain from 57 MHz, to a 1 gain around 400 MHz, all the way to an gain of 8 at 887 MHz.

    This is the first time I've attempted to design something using transistors, most of what we've done until this point has been problems, and I did pretty well on most of them, except this section (high frequency response of BJT's).

    So if someone could step me through the high frequency design process of such a circuit, or critique the circuit I have so far and tell me what I am doing wrong it would be very much appreciated.

    My current transistor I am working on:

    (I know this is an IC, but I used the PSpice data provided, and recreated this transistor in Multisim, and by using the circuit diagram given, altered the inductors and capacitors to come up with the best overall gain available.

    Thanks in advance,

  2. sixstringartist


    Apr 8, 2008
    Does the project allow for only a single stage amplifier?
  3. dhice

    Thread Starter New Member

    Apr 13, 2008
    Yes, he limited it to a single BJT :(