bidirectional blocking MOSFET

Discussion in 'General Electronics Chat' started by bug13, Mar 16, 2013.

  1. bug13

    Thread Starter Well-Known Member

    Feb 13, 2012
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    Hi guys

    Is there a MOSFET that can block an bidirectional current flowing when it's off? If not, what other choice do I have? I don't want to use a diode in series if possible.

    Thanks
     
  2. thatoneguy

    AAC Fanatic!

    Feb 19, 2009
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    As a single package? Sounds like you are looking for a TRIAC or SSR?
     
  3. bug13

    Thread Starter Well-Known Member

    Feb 13, 2012
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    Not necessary in a single package, can be a combination of a few components, I just want to minimize the voltage drop/losses at low current.

    Triac and SSR might be a bit to slow, I am looking for 200KHz switching frequency.

    edit:

    My tutor told me that I can get an Enhancement MOSFET without a body diode, but isn't the the diode part of the MOSFET internal construction??
     
    Last edited: Mar 16, 2013
  4. ScottWang

    Moderator

    Aug 23, 2012
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    How's the V,I of your circuit?
    And how's the V cross on mosfet and I flow into mosfet?
    What you need is MOSFET,FET,JFET,or FET in cmos?
     
  5. ErnieM

    AAC Fanatic!

    Apr 24, 2011
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    I've always wanted to try two MOSFETs in series to control an AC signal:


    [​IMG]
     
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  6. crutschow

    Expert

    Mar 14, 2008
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    You can also connect two MOSFETs of the same polarity in series back-to-back with their sources connected together, putting their body diodes back-to-back. This blocks current in both directions when the MOSFETs are off but FETs will conduct in either direction when ON (source and drain are interchangeable).
     
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  7. bug13

    Thread Starter Well-Known Member

    Feb 13, 2012
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    The Imax = 5A, Vmax=30V, what do you mean by MOSFET,FET,JFET,or FET in cmos?
     
  8. bug13

    Thread Starter Well-Known Member

    Feb 13, 2012
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    That looks interesting, is there special requirements to drive this, in term of switching loss? Do these configuration have a technical name for me to do some googling??
     
  9. ScottWang

    Moderator

    Aug 23, 2012
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    Different purpose and current using different parts.
    I saw many people that they want to find a diodeless mosfet as you, but it seems only JFET has the character, and I checked the current of JFETs but their current is small for you.

    Someone said that you can using IGBT, but the IGBT is too expensive.

    There is a theory but I haven't try it yet, that is reversing DS, if you want to used it in AC signal, maybe you need more MOSFETs.

    You can see the internal structure of CD4066 or 74HC4066, it's a small current logic and ac switch.
    CD4066 datasheet.
     
  10. bug13

    Thread Starter Well-Known Member

    Feb 13, 2012
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    Can you show me a circuit please? thanks
     
  11. Jony130

    AAC Fanatic!

    Feb 17, 2009
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  12. crutschow

    Expert

    Mar 14, 2008
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    Below is the simulation of a bidirectional switch using two back-to-back P-MOSFETs. Looking at the current through V3 [I(V3)] you can see that it blocks in both directions when their gate-source voltage is 0V (Vg at 10V) and conducts in both directions when their gate-source voltage is -10V (Vg at 0V).

    You can also use two N-MOSFETS back-to-back but the voltages would all be inverted. The operating criteria is that the switch is OFF when the gate-source voltages are at zero (or less) and the switch is ON when the gate-source voltage is at or above the full turn-on gate source voltage (typically 10V for standard MOSFETS and 5V for logic-level MOSFETS). Of course the proper gate-source polarity must be maintained to turn on the MOSFETS (Vgs is plus for N-MOSFETS and minus for P-MOSFETS). Also you must never exceed the maximum Vgs rating (typically ±20V for most MOSFETS).

    Bidirectional MOSFET Sw.GIF
     
    Last edited: Mar 19, 2013
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