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Darlington transistors, why not?

Discussion in 'Amplifiers' started by Tallman, Jun 5, 2018.

  1. Tallman

    Tallman W9WDX Amateur Radio Member, KW4YJ EXTRA class

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    You have lots of gain, and you don't need a lot of watts to drive them. Okay some where I heard that the FCC has a 15 db maximum gain standard that you should not exceed.
    But if you are lighting up the sky with Giga-watts on 11 meters what do you care about a 15 db rule?
    The component count should be lower and I think you should be able to get a clean signal out of it.
    I had a car stereo amplifier that had Darlington transistors and big transformers and it sounded great.
    It was a KRACO PBS-90 and it would run you out of the truck no matter how loud you like it. I used this truck in the oil fields of South Texas and when we would be cleaning our service vehicles my doors were open and we rocked out while cleaning. It could drown out the sound of a power washer with no problem!
    I'm sorry I digress, the point being hostile environment, rugged use and no failures.
    So why not use Darlingtons?
    https://analyseameter.com/2016/01/darlington-transistor-switch-and-configuration.html


     

  2. Captain Kilowatt

    Captain Kilowatt Professional Amateur
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    From your link above:
    Darlington Transistor applications
    Darlington transistor is used in various applications where a high gain is required at a low frequency. Following of the applications are:

    • Light and touch sensors
    • Controlling of motors
    • Power Regulators
    • Display Drivers
    • Controlling of solenoids
    • Audio amplifiers output stages
    Note it says LOW frequencies. Darlingtons work great as switches but not so great as RF amps. Their configuration does not allow for proper biasing for one thing. When used as audio amps they are essentially acting as switches in a high class such as D or even higher. The switch time of them is far too slow for use at RF.
     
    Tallman likes this.
  3. Tallman

    Tallman W9WDX Amateur Radio Member, KW4YJ EXTRA class

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    Now that is a bummer. I was hoping there was a way. There would be so many advantages with the high gain.
     
  4. nomadradio

    nomadradio Analog Retentive

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    As gain rises, bandwidth falls. Double the gain, bandwidth falls in half.

    General rule. This is the main reason you see the Darlington configuration used mostly in DC/audio circuits and almost never in a RF circuit.

    73
     
  5. Captain Kilowatt

    Captain Kilowatt Professional Amateur
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    They work great as relay drivers in a amp's switching relay however that's about as close to an RF application as you will get.
     
  6. Onelasttime

    Onelasttime Well-Known Member

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    In the 1990's Darlington Transistors where all the rage in hi-end car audio amplifiers, This was especially true of hi current American made products like Pheonix Gold, HiFionics, Orion Red.
     
: amp, fets, transistors

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