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  1. yasir_66

    Thread Starter Active Member

    Jun 25, 2009
    71
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    these are schematics.Plz audioguru redesign receiver ckt. & tell me which transistor# is wrong biased?
     
    Last edited: May 11, 2010
  2. ELECTRONERD

    Senior Member

    May 26, 2009
    1,146
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    No schematics are evident, try reposting them.
     
  3. Audioguru

    New Member

    Dec 20, 2007
    9,411
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    The schematics were saved and were posted as small fuzzy JPG file types. JPG has losses that make the image fuzzy so its numbers cannot be seen.

    You should have saved and posted the schematics as a very clear PNG file type and made larger.

    The first transistor in the receiver is biased so that it is almost saturated. Also the values for its base bias resistors are too high.

    Transistors should not be used as a preamp today, a low noise wide bandwidth opamp should have been used.
     
  4. Ron H

    AAC Fanatic!

    Apr 14, 2005
    7,050
    657
    If you still want to use that receiver circuit, I redesigned it for you. It is optimized for a 40kHz piezo ultrasonic transducer. If you want to use a tweeter, it will need an input coupling capacitor.
    It has a lot of gain at the Q2 collector (≈40dB), even with the gain pot set at 10k. With the gain pot set at zero, the gain iis about 70dB. You might need to use a different gain control scheme if the gain is too high.
     
  5. yasir_66

    Thread Starter Active Member

    Jun 25, 2009
    71
    1
    ok thnx buddy.yes i have piezo transducer in which metal surface is shorted to gnd.
     
  6. yasir_66

    Thread Starter Active Member

    Jun 25, 2009
    71
    1
  7. bertus

    Administrator

    Apr 5, 2008
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