High speed MOSFET and MOSFET driver

Discussion in 'The Projects Forum' started by craq, May 11, 2009.

  1. craq

    Thread Starter New Member

    May 11, 2009
    2
    0
    Hi,
    I want to build a switching circuit that is as fast as possible (off->on in ~1ns would be nice, must be less than 40ns). Maximum loads will be 0.5A and 60V. I have no idea what the requirements are to build a circuit for this speed, so hopefully the people here can help out, first of all with part selection. I believe N-channel is faster than P, which means I put the switch between the load and ground?

    I just found out today that fast MOSFETs need a separate driver (to provide charge in a burst to the gate capacitance). Actually I will have a low frequency (i.e. repetition rate), and high switching speed, but I think I still need the driver? Are there any options where they are integrated?

    My first attempt would be:
    switch: http://www.st.com/stonline/products/literature/ds/6772/stn1n20.pdf
    driver: http://www.nxp.com/acrobat_download/datasheets/PMD2001D_1.pdf

    Hope someone can give me some tips
     
  2. thingmaker3

    Retired Moderator

    May 16, 2005
    5,072
    6
    The combination of devices will provide the specified switching speeds and working voltage/current. Note the Rds-on of the MOSFET is pretty high: 1.2Ω - will this be acceptable in your application?
     
  3. craq

    Thread Starter New Member

    May 11, 2009
    2
    0
    Thanks for the confirmation. I had to have a look what Rds is, but I think if it acts simply a DC resistance then I should have a strong enough power supply to push the current through.

    Of course, if you had another suggestion with lower Rds, that'd be great. (But this will be part of a larger order to RS Electronics Germany, so it has to be part of their range.)
     
  4. thingmaker3

    Retired Moderator

    May 16, 2005
    5,072
    6
    It does act very much like a DC resistance. Since 60V / .5A = 120Ω, 1.2Ω is about 10% of your load. I am not familiar with RS's product line.
     
  5. mik3

    Senior Member

    Feb 4, 2008
    4,846
    63
    Have you considered power dissipation in the MOS?

    Can it handle the load? Maybe a heatsink?

    By the way what is your application and you need such high speed devices?
     
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