SiGe HBT transistor

Discussion in 'The Projects Forum' started by 3BwEH, Mar 16, 2008.

  1. 3BwEH

    Thread Starter Active Member

    Feb 25, 2007
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    i am using this transistor to design a broadband amplifier
    i was wondering how can i test it if its not working

    i mean how can i make sure that the transistor is faulty and not the circuit itself

    thanks

    :cool:
     
  2. SgtWookie

    Expert

    Jul 17, 2007
    22,183
    1,728
    Do you have a datasheet for the transistor, or at least a manufacturer and part number?

    This is a pretty new technology. Test parameters for the device should be given in the datasheet. However, with devices of that kind of speed, you'll be hard-pressed to find tools to measure it with at the high frequency end.
     
  3. 3BwEH

    Thread Starter Active Member

    Feb 25, 2007
    33
    0
    well the device is bfp620 from infineon company
    the data sheet is on the website but i cant find the S-parameters on the data sheet
     
  4. SgtWookie

    Expert

    Jul 17, 2007
    22,183
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    Found the datasheet:
    http://www.infineon.com/cms/en/product/findProductTypeByName.html?query=bfp620

    Well, it DOES contain a SPICE model they claim is valid up to 6GHz, along with what seems to be a reasonable schematic representation of the device and associated parasitics.

    The S-parameters are going to depend upon the entire circuit, not just the transistor itself. When you're working in the GHz range, parasitics that would be insignificant at say, 100MHz become enormous. You really can't use standard multilayer ceramic caps, as their parasitic L and R becomes huge; so you'll need to use SLC's (single-layer capacitors). You'll have to account for the L and C of your PCB traces - but if you're operating in the GHz range, you should be using something like a ceramic substrate rather than something like FR4.
     
  5. 3BwEH

    Thread Starter Active Member

    Feb 25, 2007
    33
    0
    well thanx for your reply
    But My question is after building the whole amplifier and lets say that the amplifier didnt work .. is there some way to test the transistor itself to make sure that the fault is either from the transistor itself or not?!
     
  6. scubasteve_911

    Senior Member

    Dec 27, 2007
    1,202
    1
  7. SgtWookie

    Expert

    Jul 17, 2007
    22,183
    1,728
    So, did you build an amplifier and it didn't work?

    Where's your schematic, your PCB layout, a photo of your completed circuit, and what you've done to troubleshoot it so far?
     
  8. 3BwEH

    Thread Starter Active Member

    Feb 25, 2007
    33
    0
    actually am doing the feasiblity study and ill start building it on June
    thanx a lot for ur help ill show u my work when am done
    thanx again
    :D
     
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