PLEASE HELP IN A JFET AMPLIFIER DESIGN for 2-watt speaker

Discussion in 'Homework Help' started by bradix23, Jan 24, 2011.

  1. bradix23

    Thread Starter New Member

    Jan 24, 2011
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    Hi!... Guys, can you help me design a JFET amplifier?.. I need to amplify the output of an IPOD so it can run a 1-watt speaker or maybe 2-watt speaker. Im having a hard time in finding the right JFET suitable for this audio amplifier.

    I would like to know which should i use as IDSS and VGS: Is it the (min), (typ), (max). I dont really understand whats written in the specifications but i do know a little about designing the resistors RD and RS.

    Please Help!... :))

    *Does anyone know what is the exact output signal of a full-volumed IPOD?*

    THANKS!
     
  2. Jony130

    AAC Fanatic!

    Feb 17, 2009
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    Are you sure that you want JFET power amp ??
    The power JFET are very rare transistors, not so easy to buy.
     
  3. Audioguru

    New Member

    Dec 20, 2007
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    I have seen thousands of power transistors, hundreds of power Mosfets and hundreds of low power Jfets.
    But I have never seen a power Jfet.

    I found a Jfet power amplifier in Google. It used a power Jfet that is discontinued. The performance of the amplifier was not good.
     
  4. thatoneguy

    AAC Fanatic!

    Feb 19, 2009
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    Is there a specific reason you want to use a JFET over other discrete options?

    Have you considered the "Amp on a chip" solutions?
     
  5. Audioguru

    New Member

    Dec 20, 2007
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    Maybe the teacher said to design an amplifier with Fets. Then common ordinary Mosfets should be used, not odd Jfets.
     
  6. Adjuster

    Well-Known Member

    Dec 26, 2010
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    Perhaps he has heard about recent developments in SiC power JFETS, developed for large SMPS use, e.g. by SemiSouth?

    These would hardly be candidates for use in a 2W speaker amplifier, even if it were possible for him to get hold of any.
     
  7. thatoneguy

    AAC Fanatic!

    Feb 19, 2009
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    Instructions for a 2N7000 Amp

    It shows all the steps for calculating a single stage MOSFET small signal amp. This is NOT a Power Amp, but gives you an idea what a design should 'look like' and how to read a datasheet.
     
  8. bradix23

    Thread Starter New Member

    Jan 24, 2011
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    So, does this means i need to use a MOSFET? there are two mosfets that i know, d-mosfet and e-mosfet. Which should i use?...

    Also, is there other any projects that uses JFET that is simple and useful? Please include its application. Ive been in this project for 1 week and i got stuck on what FET should i use.
     
  9. bradix23

    Thread Starter New Member

    Jan 24, 2011
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    What are those "common ordinary MOSFETS"?
     
  10. Audioguru

    New Member

    Dec 20, 2007
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    There are thousands of "common ordinary" Mosfets used as on-off switches but only a few used in power amplifiers to drive speakers.
    Power transistors work better and easier in a power amplifier circuit.

    www.redcircuits.com have a few Mosfet power amplifier circuits.
     
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