Article: What Do Overclockers and Supercomputers Have in Common?
By: David Hess (, June 24, 2011 2:14 pm
Room: Moderated Discussions
Adrian ( on 6/24/11 wrote:
>David Hess ( on 6/22/11 wrote:
>>Now I am confused. How does that explain the negative temperature coefficient
>>for MOSFET channel resistance? It can not be because of threshold voltage change
>>because it occurs in saturation. It does however become a positive temperature coefficient at very high voltages.
>>Or does the above only apply to power MOSFETs and not to the submicron ones used in logic processes?
>>How does this relate to gain increasing in bipolar transistors with increased temperature?
>>Secondary breakdown is a very real problem in bipolar power transistors.
>The temperature coefficient of the channel resistance of MOSFETs is *positive*, not negative.
>For power applications this is a major advantage of MOSFETs, because it allows
>their connection in parallel without the danger that the current will pass mostly through a single device.

Sorry about that. I was thinking the right thing but somehow reversed it when writing it down. :) I was up all night diagnosing a Tektronix 2230.

>For logic circuits this leads to the familiar behavior that they are faster at
>low temperatures, where the channel resistance is small, so the RC products are
>also small, thus the switching times become smaller.
>Nevertheless, there are certain operating points (e.g. close to breakdown or in
>subthreshold mode) where the channel resistance may *seem* to have a negative temperature
>coefficient. However, in those cases, what you see is not the current that corresponds
>to the drain-source voltage divided by the channel resistance, but a current whose
>largest part is due to other effects, e.g. due to the parasitic bipolar transistor
>that exists in parallel with any MOSFET. Whenever the leakage current through the
>parasitic bipolar transistor is not negligible compared to the drain current, you
>will see a negative temperature coefficient.

Unfortunately my two Siliconix books are in a box somewhere or I would have looked it up. I just remembered that the current sharing fails at high voltages and something similar to secondary breakdown becomes possible.
< Previous Post in ThreadNext Post in Thread >
TopicPosted ByDate
Article: Cooling and performance/wattDavid Kanter2011/06/21 12:19 PM
  'temperature' not 'power'?Paul A. Clayton2011/06/21 03:01 PM
    'temperature' not 'power'?David Kanter2011/06/21 03:38 PM
  resistance(temperature)Moritz2011/06/22 04:48 AM
    resistance(temperature)Adrian2011/06/22 05:13 AM
      resistance(temperature)David Hess2011/06/22 08:53 AM
        resistance(temperature)Adrian2011/06/24 02:24 AM
          resistance(temperature)David Hess2011/06/24 02:14 PM
  Article: Cooling and performance/wattEd Trice2011/06/22 10:57 AM
    CoolingDavid Kanter2011/06/22 03:26 PM
      CoolingEd Trice2011/06/22 03:54 PM
      TE-elementsMoritz2011/06/23 05:55 AM
        Radiator placement and designRicardo B2011/06/23 07:34 AM
        TE-elementsEduardoS2011/06/23 04:21 PM
          water/airMoritz2011/06/23 10:30 PM
            water/airRicardo B2011/06/24 02:29 PM
              water/airbakaneko2011/06/24 09:45 PM
                water/airDavid Hess2011/06/25 04:12 AM
                water/airRicardo B2011/06/25 06:07 AM
                  water/airZaZa2011/06/25 09:47 AM
                    water/airRicardo B2011/06/25 11:40 AM
                      water/airrwessel2011/06/26 03:43 AM
                      water/airZaZa2011/06/26 04:05 PM
  Temperature inversionJonathan Kang2011/06/22 05:43 PM
    LN2 overclockingDoug Siebert2011/06/25 01:32 PM
    Temperature inversionVincent Diepeveen2011/06/27 01:01 PM
    Temperature inversionAnon2011/06/28 03:30 PM
      Temperature inversionJonathan Kang2011/07/05 06:38 PM
  Article: Cooling and performance/watt(tm)2011/06/27 05:51 AM
  Article: Cooling and performance/wattDavid2011/10/15 06:14 PM
    Article: Cooling and performance/wattrwessel2011/10/15 09:56 PM
  Exponential growth of subthreshold leakageKonrad Schwarz2011/12/15 07:56 AM
    Exponential growth of subthreshold leakageRohit2011/12/15 01:22 PM
      Exponential growth of subthreshold leakageDavid Kanter2011/12/15 04:20 PM
        Exponential growth of subthreshold leakageIain McClatchie2013/01/07 12:28 AM
          Exponential growth of subthreshold leakageDoug S2013/01/07 10:25 AM
          Exponential growth of subthreshold leakagesomeone2013/01/07 11:12 PM
  Article: Cooling and performance/wattRobert Pearson2021/07/26 09:45 AM
Reply to this Topic
Body: No Text
How do you spell tangerine? 🍊