Groups > sci.electronics.design > #452193

Parasitics?

From	rickman <gnuarm@gmail.com>
Newsgroups	sci.electronics.design
Subject	Parasitics?
Date	2017-03-16 19:44 -0400
Organization	A noiseless patient Spider
Message-ID	<oaf7ro$efu$1@dont-email.me> (permalink)

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I'm running a simulation where I'm pumping charge into a capacitor to 
generate a voltage.  A transistor emitter/source is connected to the 
positive rail and the collector/drain is connected to a 1 nF cap through 
a 47k resistor.  When the base/gate is driven high to shut off the 
current I see the current go up initially then taking almost 2 us to 
shut off.  I've tried 2N3906 and BSS84 and a couple others selected 
randomly.  The switching period is around 8 uS.

Is this from the parasitic capacitance in the transistor?  The BSS84 
only has 1 nC gate charge and still the effect is very pronounced.

Is there a way to mitigate this effect other than using a larger cap and 
smaller resistors?

-- 

Rick C

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Parasitics? rickman <gnuarm@gmail.com> - 2017-03-16 19:44 -0400
  Re: Parasitics? bloggs.fredbloggs.fred@gmail.com - 2017-03-16 16:48 -0700
  Re: Parasitics? Sylvia Else <sylvia@not.at.this.address> - 2017-03-17 10:59 +1100
    Re: Parasitics? rickman <gnuarm@gmail.com> - 2017-03-16 20:19 -0400
  Re: Parasitics? Sylvia Else <sylvia@not.at.this.address> - 2017-03-17 12:21 +1100
    Re: Parasitics? rickman <gnuarm@gmail.com> - 2017-03-16 23:16 -0400
      Re: Parasitics? Sylvia Else <sylvia@not.at.this.address> - 2017-03-17 14:51 +1100
        Re: Parasitics? rickman <gnuarm@gmail.com> - 2017-03-17 00:57 -0400
          Re: Parasitics? bloggs.fredbloggs.fred@gmail.com - 2017-03-18 01:36 -0700
            Re: Parasitics? rickman <gnuarm@gmail.com> - 2017-03-18 05:45 -0400
              Re: Parasitics? bloggs.fredbloggs.fred@gmail.com - 2017-03-18 06:33 -0700
                Re: Parasitics? rickman <gnuarm@gmail.com> - 2017-03-18 12:22 -0400
                Re: Parasitics? Sylvia Else <sylvia@not.at.this.address> - 2017-03-24 13:30 +1100
                Re: Parasitics? rickman <gnuarm@gmail.com> - 2017-03-24 00:36 -0400
                Re: Parasitics? Sylvia Else <sylvia@not.at.this.address> - 2017-03-24 16:10 +1100
  Re: Parasitics? "Tim Williams" <tiwill@seventransistorlabs.com> - 2017-03-17 01:42 -0500
    Re: Parasitics? rickman <gnuarm@gmail.com> - 2017-03-17 04:11 -0400
  Re: Parasitics? Phil Hobbs <pcdhSpamMeSenseless@electrooptical.net> - 2017-03-17 09:53 -0400
    Re: Parasitics? Cursitor Doom <curd@notformail.com> - 2017-03-17 18:52 +0000

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