Happy yet disappointing arrival :(

Discussion in 'General Electronics Chat' started by cjdelphi, Feb 20, 2011.

  1. cjdelphi

    Thread Starter New Member

    Mar 26, 2009
    272
    2
    3 weeks back (ugh) I bought 2 lots of these

    http://cgi.ebay.com.au/ws/eBayISAPI.dll?ViewItem&item=290412411585&ssPageName=STRK:MEWNX:IT


    Today the package arrived, I got quite excited at the prospect of building a small 2ghz amplifier with the 4 BFG480W IC's that just arrived, here's the 'picture'



    Anyway, I open up the package expecting to stick them on my breadboard and start playing with these IC's... I open the package, where are they? feels a bit um 'empty' getting worried maybe they only delivered 2 not the 4... open up another bag inside that bag is a smaller bag eventually I get to them..

    Bit small for an IC with 4 pins? ooooooohhhhhh SURFACE MOUNTED!! - ugh almost useless for my level of skill lol

    OK the responsibility is mine, I should have checked the PDF and looked at the physical dimensions.. but seriously now, that picture is just so misleading. (seriously this!)
    [​IMG]
    lol

    Right now i have 4 of them wide band transistors now capable of boosting 900mhz - 2.5ghz (I hope) but it peaks at 2ghz.. but, these things are quite difficult to find to be honest, anyone know if anything larger of this transistor is available? I want something the size of a 555 IC.. failing that I could just re-sell it to someone else, $12 bucks cost me all up for this.
     
  2. cjdelphi

    Thread Starter New Member

    Mar 26, 2009
    272
    2
    for some reason my image is not showing up... take a look at the ebay page lol... is it worth trying to solder little wires off the legs? so i can use it on my breadboard, my first idea was to boost a wifi signal now im not so sure.
     
  3. thatoneguy

    AAC Fanatic!

    Feb 19, 2009
    6,357
    718
    The graphic on the auction shows that it is a 4 pin SOT-23 size device, the "gull wings" (rather than straight pins) tell a lot with a glance. The auction description states it is a SOT-343 (Small Outline Transistor).

    Several companies sell Surfboards, which allow SMD components to be used in breadboards or other prototype work.

    If you are just starting out though, I'd suggest doing a good number of simpler projects instead of trying to work in the GHz RF range.
     
  4. SgtWookie

    Expert

    Jul 17, 2007
    22,182
    1,728
    Even very short wires will have a profound effect in the GHz range.

    There is absolutely no way to use a "breadboard" at those frequencies.

    After you pass about 500MHz, the parasitic properties of components come strongly into play, and they just don't act like you would expect them to at lower frequencies. Multilayer ceramic capacitors may seem to double or triple in value. A 10mm length of wire becomes a 15nH inductor.

    The GHz frequency range is not for the un-initiated. Without sophisticated (and expensive) test equipment, you won't have a clue what's going on, or even where things went wrong.
     
  5. cjdelphi

    Thread Starter New Member

    Mar 26, 2009
    272
    2
    ok you've convinced me lol.. :p not even going to bother trying now lol....
     
  6. SgtWookie

    Expert

    Jul 17, 2007
    22,182
    1,728
    Here's a link to the datasheet:
    http://www.nxp.com/documents/data_sheet/BFG480W.pdf

    Have a look at page 12; there's a 2GHz test circuit.
    The three traces running down the center are microstrip; basically what amounts to a tuned circuit, similar to coaxial cable.

    Note the very thin rectangular traces towards the center of the board; those are inductors.

    Everything is tuned for 50 Ohms impedance. The dimensions have to be very precise, the PCB material has to be exactly as specified, or the impedance of the circuit will be incorrect. That impedance mismatch could lead to large amounts of reflected RF energy, which could destroy the transistor.
     
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