Diode as a SPST switch not a rectifier

Discussion in 'General Electronics Chat' started by watsongrey, Nov 3, 2014.

  1. watsongrey

    Thread Starter Member

    Oct 31, 2014
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    How do you use Diodes as switches and not a rectifier?
    They can use Diodes as a SPST switch, but how?
    I thought Diodes rectify any bi-directional or bi-polar waveform
    I can't tell when looking at a schematic if the diodes are a switch or if they are rectifying the waveform, how can a technician tell?
    What is a Diode bridge used for?
     
  2. Lestraveled

    Well-Known Member

    May 19, 2014
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    A diode can be used as a SPST switch by controlling the bias. A diode will be on if it is forward biased and off when it is reversed biased.
     
  3. MikeML

    AAC Fanatic!

    Oct 2, 2009
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    ...which imposes the requirement that the bias current be switched somewhere else, and that the bias current be at least 10X bigger than the the current caused by the signal being switched.


    ps, might you be BillyMayo, or LeoWilson, or VinnyWilliams, or DanWalker, or several other aliases? that fellow is using these forums to learn what should better be learned in school, or self-study?
     
    Last edited: Nov 3, 2014
  4. watsongrey

    Thread Starter Member

    Oct 31, 2014
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    When using a Diode as a switch you need pull up resistor and a pull down resistor to bias the diode?
    When using a Diode as a switch, it still "rectifies" the waveform or does it pass an AC waveform right through the diode?
     
  5. alfacliff

    Well-Known Member

    Dec 13, 2013
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    use a couple of coupling caps, on on input and one on output, and it will switch audio or rf. when biased on and off of course.
     
  6. watsongrey

    Thread Starter Member

    Oct 31, 2014
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    So when a diode is biased with a positive and negative supply bias it will pass an alternating waveform and not rectify it?
     
  7. ian field

    Distinguished Member

    Oct 27, 2012
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    As long as the half-cycle opposing the bias doesn't exceed the bias.
     
  8. watsongrey

    Thread Starter Member

    Oct 31, 2014
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    Yes so it doesn't clip the positive or negative cycles

    What is a Diode Bridge used for?
     
  9. ian field

    Distinguished Member

    Oct 27, 2012
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    Which one? - there's the regular full-wave bridge rectifier, and there's the diode ring mixer used in radio work.

    As a further twist - the regular bridge rectifier can also be configured as an DC controlled attenuator.
     
  10. ISB123

    Well-Known Member

    May 21, 2014
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    Diode bridge is used to turn AC into DC.
    Basically it works by flipping the negative wave into a positive one,now that is the case in full wave rectifiers.
    If you have 50 Hz and you rectify it with full wave rectifier you are going to end up with 100 Hz because negative waves were inverted in positive waves and filled the empty spot left by the AC.
    There are half wave rectifiers too they will just "block out" the negative wave and leave you with positive wave.
    You will have to use a capacitor to flatten the waves into a proper DC signal.
    [​IMG]
    Now this is a very crude explanation you can search for more info about bridge rectifiers on the net.
     
  11. watsongrey

    Thread Starter Member

    Oct 31, 2014
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    No, I'm not talking about a rectifier Diode bridge

    Diode bridge is like a SPDT or DPDT switch i heard when used as a Diode Ring mixer
    They use a Diode bridge like a switch

    I'm not sure how it's used as a switch
     
  12. ian field

    Distinguished Member

    Oct 27, 2012
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    I'd start by looking at ARRL (or RSGB) publications for articles explaining them.
     
  13. bertus

    Administrator

    Apr 5, 2008
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    Hello,

    Read the following pdf's.

    Bertus
     
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