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Mosfet and Discrete Fet, Same Thing ?????

Discussion in 'Amps and Cabs [BG]' started by shoot-r, Mar 30, 2013.

  1. shoot-r


    May 26, 2007
    Gallien-Krueger's MB-800 head uses a "Discrete Fet" driven pre-amp.....

    Ampeg's PF-800 head uses a "Mosfet" pre-amp.....

    Is "Discrete Fet" and "Mosfet" the same componet?

    If not, what would be the sound differences be?
  2. Mr. Foxen

    Mr. Foxen Commercial User

    Jul 24, 2009
    Bristol, UK
    Amp tinkerer at Ampstack
    Moset is metal oxide field effect transistor. Discrete fet just means each transistor is its own thing rather than a chip with a bunch of them, they could be other types of fet than metal oxide ones. Sound is entirely dependent on what they are doing, and the spec of the individual fets, and not much to do with their composition.
    Killed_by_Death likes this.
  3. fdeck

    fdeck Supporting Member Commercial User

    Mar 20, 2004
    Madison WI
    HPF Technology LLC
    FET = Field Effect Transistor, which achieves gain by an electric field on a "gate" terminal to control the conductivity of a "channel" of semiconducting material. The gate is insulated from the channel. In a Junction FET (JFET), the gate is insulated by a diode junction formed between the gate and the channel. In a metal oxide semiconductor FET (MOSFET), the insulation is a thin layer of a non-conducting material, originally aluminum oxide.

    As Mr. Foxen says, "discrete" typically means that a circuit does not use integrated circuits.

    Historically, preamps containing FETS used JFETs. A preamp containing MOSFETs would be somewhat unusual, but not impossible. It could be discrete or IC. There are IC op amps composed entirely of MOSFETs.

    In some circles, different tone qualities are ascribed to different components. Because FETs have a transfer function similar to tubes, advertising FETs is a way to gain some marketing advantage from the association with tube gear.
    Killed_by_Death likes this.

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