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How would drive this MOSFET?

Discussion in 'Electronic Design' started by Harry Dellamano, Apr 11, 2006.

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  1. Given the IRF6156 Bi-Directional N-channel Switch found here:
    http://www.irf.com/product-info/datasheets/data/irf6156.pdf
    Let's say you had a +/-15V sine 1KHz source driving a 5.0R resistor thru
    this bi-directional switch to ground. How would you drive the gates to
    perform bi-directional switching? When switched "on" both channels must be
    on, parasitic diodes do not count.
    Why didn't they make it a common source so it is easly driven?
    Regards,
    Harry
     
  2. legg

    legg Guest

    I guess it's just easy to make.

    Applications seem to be limited to switching the negative terminals
    of various sources. This would play hell with any smart battery
    communications.

    http://www.irf.com/technical-info/whitepaper/pcime2001final.pdf

    Even isolated parts would be more useful.

    RL
     
  3. Maybe they're just calling the outer terminals the sources since they
    are at an externally controlled voltage. The voltage of the inner
    terminals, in the off state, would be determined by the chance balance
    of leakage currents between the two devices.
     
  4. The outside terminals are the sources and as Legg points out this MOSFET
    must be driven by a special driver and not suibule for most Bi-directional
    uses. The inner drains never float but are constrained by the parasitic
    diodes and are one diode drop less voltage than the most positive source.
    Harry
     
  5. Yes, I was forgetting the diodes. But they're not parasitic, they're
    intentional ESD diodes. Anyway, it does look as if this thing isn't for
    general use.
     
  6. Tell us where you can obtain MOSFETs without parasitic diodes, we all want
    to know.
    Harry
     
  7. Jim Thompson

    Jim Thompson Guest

    SOI ?:)

    ...Jim Thompson
     
  8. Say what, Silicon On Insulator??
    Harry
     
  9. Jim Thompson

    Jim Thompson Guest

    Yep. I've done one GPS receiver on a SOI CMOS process.

    SOI is also often used in circuits requiring RAD-HARD.

    ...Jim Thompson
     
  10. What do you mean by parasitic? There have been mosfets without
    protection diodes. I blew out a number of them in the 1970's.
     
  11. That's it then, you blew them all up and there's none left. You must have
    worked on RTL and DTL because there are none of those around either.
    Sorry for the Boki writing style, we went to different schools together.
    Harry
     
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