Transistors are not current amplifiers

Discussion in 'Off-Topic' started by italo, Jan 14, 2009.

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  1. italo

    Thread Starter New Member

    Nov 20, 2005
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    A transistor is not a current amplifier but ruther a voltage amplifier. What you get at the collector is the results of current flow which is gain. Beta is an impirical number assigned to a paticular load transfer function. It means nothing unless a load current is specified. The device takes more current to so it amplify voltage. Tubes are current amplifiers it takes a presence of voltage to amplify the curent. Many non thinker will disagree with that.
     
  2. beenthere

    Retired Moderator

    Apr 20, 2004
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    I moved your post here, as it deserves separate discussion. This was the original thread - http://forum.allaboutcircuits.com/showthread.php?t=18021.

    Your assertion that tubes, and not transistors amplify current is contrary to theory and practice. Likewise that transistors are voltage amplifiers. Can you cite material that demonstrates the veracity of your assertion?

    Few of us here characterize ourselves as non-thinkers.
     
  3. RiJoRI

    Well-Known Member

    Aug 15, 2007
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    Most non-thinkers will say "Huh?" and go do something else.

    --Rich
     
  4. studiot

    AAC Fanatic!

    Nov 9, 2007
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    One of the members of another forum I frequent is called

    oh_no_not_her_again

    I think this applies here
     
  5. thingmaker3

    Retired Moderator

    May 16, 2005
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    Italo, you might gain more agreement by suggesting "A transistor may be also modeled as a voltage amplifier."
     
  6. Wendy

    Moderator

    Mar 24, 2008
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    Show me an equation that can derive all the biasing schemes for BJTs from the basic premise Ic = β Ib with any accuracy and doesn't involve calculus.

    This particular premise has been argued to death and beyond here, usually by people who have never designed with transistors.
     
  7. Ratch

    New Member

    Mar 20, 2007
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    italo,

    Pardon me for not answering sooner, but I just got back from a week of vacation in Puerto Vallarta, Mexico.

    A transistor circuit can be made to amplify either current or voltage. Many enlightened semiconductor users agree that a BJT transistor operated in the active region is a voltage controlled entity. Many documents show and prove that the collector current is exponentially dependent on Vbe. Since the diversionary or unavoidable waste current, which is called the base current, is also exponentially dependent on Vbe, the collector current and the base current have a linear relationship, but do not control each other.

    Charge flow by itself is not gain. Gain is a comparison between output amplitude and input amplitude. Beta is the gain of the collector current to the base current, which are both controlled by Vbe. Beta is useful for design purposes if it is guaranteed to be high enough within an operating range for a transistor application.

    Meaningless sentence with no context.

    The above are contradictory clauses stitched together to make a nonsensical sentence. The only current controlled entity I can think of offhand is a magnetic amplifier. A vacuum tube is a voltage controlled device.

    Ratch
     
  8. Dave

    Retired Moderator

    Nov 17, 2003
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    There is already an active thread in F&S on this (see here); we don't want another thread with the same bickering, misinformation, and semantic debates.

    Dave
     
    Last edited: Jan 17, 2009
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