Groups > sci.electronics.design > #452794

Re: Low Threshold MOSFET

From	Hul Tytus <ht@panix.com>
Newsgroups	sci.electronics.design
Subject	Re: Low Threshold MOSFET
Date	2017-03-20 22:47 +0000
Organization	PANIX Public Access Internet and UNIX, NYC
Message-ID	<oapm6n$j4c$1@reader1.panix.com> (permalink)
References	<oanlv1$af7$1@dont-email.me> <eja0boFi5kdU1@mid.individual.net> <oapa8h$nq0$1@dont-email.me>

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Fairchild (whoever now) has a nice n channel device speced, if I remember 
correctly, at 1 volt max turn on. It served as a voltage follower op amp 
with lots of offset. They came from Mouser.

Hul

rickman <gnuarm@gmail.com> wrote:
> On 3/20/2017 8:30 AM, Lund-Nielsen, Jorgen wrote:
> > Am 20.03.2017 um 05:34 schrieb rickman:
> >> I was looking to order some low current MOSFETs and realized all the
> >> popular items had thresholds of 3 volts and higher.  I would like to use
> >> something that turns on pretty well at 3 volts so it won't need a 5 volt
> >> PSU.  Any suggestions?  I'm looking for a TO-92 case preferably but
> >> surface mount will be ok too.
> >>
> >> I could have sworn some years ago I tracked down a number of low
> >> threshold voltage FETs.  But maybe those devices operated under 5 volts
> >> rather than under 3.3 volts.
> >>
> >
> > The 2N7000 (200 mAmps, 60 Volts)
> >
> > has Gate Threshold Voltage of 0.8V min to 3.0V max
> >
> > <https://www.onsemi.com/pub/Collateral/2N7000-D.PDF>

> That's the threshold voltage where drain current begins essentially. 
> Looking at the drain current vs. drain-gate voltage typical curves the 
> current at 3.0 volts is well under 100 mA.

> I suppose I could put two or three in parallel.

> I didn't want to use an NPN because the base current goes through the 
> emitter resistor which I'm using to measure the current, but when I did 
> a simulation that current is pretty small, so I suppose it's not really 
> a problem.  The resistors are only 1% accurate.

> I've got NPNs on hand, so I'll use one for now.

> -- 

> Rick C

Thread

Low Threshold MOSFET rickman <gnuarm@gmail.com> - 2017-03-20 00:34 -0400
  Re: Low Threshold MOSFET "Lund-Nielsen, Jorgen" <jorgen.lund-nielsen@xyz123desy.de> - 2017-03-20 13:30 +0100
    Re: Low Threshold MOSFET rickman <gnuarm@gmail.com> - 2017-03-20 15:26 -0400
      Re: Low Threshold MOSFET Hul Tytus <ht@panix.com> - 2017-03-20 22:47 +0000
        Re: Low Threshold MOSFET rickman <gnuarm@gmail.com> - 2017-03-20 21:42 -0400
          Re: Low Threshold MOSFET Joerg <news@analogconsultants.com> - 2017-03-21 08:03 -0700
          Re: Low Threshold MOSFET Hul Tytus <ht@panix.com> - 2017-03-21 23:36 +0000
            Re: Low Threshold MOSFET rickman <gnuarm@gmail.com> - 2017-03-21 20:06 -0400
  Re: Low Threshold MOSFET Allan Herriman <allanherriman@hotmail.com> - 2017-03-20 12:56 +0000
    Re: Low Threshold MOSFET Winfield Hill <hill@rowland.harvard.edu> - 2017-03-20 06:34 -0700
  Re: Low Threshold MOSFET Clive Arthur <cliveta@nowaytoday.co.uk> - 2017-03-20 13:08 +0000
  Re: Low Threshold MOSFET Tim Wescott <tim@seemywebsite.com> - 2017-03-20 11:03 -0500
  Re: Low Threshold MOSFET Joerg <news@analogconsultants.com> - 2017-03-20 15:59 -0700
    Re: Low Threshold MOSFET rickman <gnuarm@gmail.com> - 2017-03-20 22:29 -0400
      Re: Low Threshold MOSFET Joerg <news@analogconsultants.com> - 2017-03-21 08:00 -0700
  Re: Low Threshold MOSFET "Tim Williams" <tiwill@seventransistorlabs.com> - 2017-03-21 01:02 -0500
  Re: Low Threshold MOSFET kevin93 <kevin@whitedigs.com> - 2017-03-22 07:15 -0700
  Re: Low Threshold MOSFET John S <Sophi.2@invalid.org> - 2017-03-22 09:36 -0500
    Re: Low Threshold MOSFET rickman <gnuarm@gmail.com> - 2017-03-22 14:03 -0400
      Re: Low Threshold MOSFET John S <Sophi.2@invalid.org> - 2017-03-22 13:43 -0500
        Re: Low Threshold MOSFET Winfield Hill <hill@rowland.harvard.edu> - 2017-03-22 12:01 -0700
        Re: Low Threshold MOSFET rickman <gnuarm@gmail.com> - 2017-03-22 15:14 -0400
        Re: Low Threshold MOSFET rickman <gnuarm@gmail.com> - 2017-03-22 15:18 -0400
          Re: Low Threshold MOSFET Joerg <news@analogconsultants.com> - 2017-03-23 10:29 -0700
        Re: Low Threshold MOSFET John S <Sophi.2@invalid.org> - 2017-03-22 15:07 -0500
      Re: Low Threshold MOSFET tabbypurr@gmail.com - 2017-03-23 20:45 -0700
        Re: Low Threshold MOSFET rickman <gnuarm@gmail.com> - 2017-03-24 00:43 -0400
          Re: Low Threshold MOSFET Robert Baer <robertbaer@localnet.com> - 2017-03-23 22:24 -0800
          Re: Low Threshold MOSFET tabbypurr@gmail.com - 2017-03-24 03:59 -0700
            Re: Low Threshold MOSFET rickman <gnuarm@gmail.com> - 2017-03-24 12:50 -0400
              Re: Low Threshold MOSFET tabbypurr@gmail.com - 2017-03-25 00:51 -0700
                Re: Low Threshold MOSFET Joerg <news@analogconsultants.com> - 2017-03-25 09:47 -0700
                Re: Low Threshold MOSFET rickman <gnuarm@gmail.com> - 2017-03-25 13:54 -0400
      Re: Low Threshold MOSFET Joerg <news@analogconsultants.com> - 2017-03-24 09:37 -0700
  Re: Low Threshold MOSFET Robert Baer <robertbaer@localnet.com> - 2017-03-22 20:40 -0800

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