John Dunn

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Consultant

John Dunn is an electronics consultant, and a graduate of The Polytechnic Institute of Brooklyn (BSEE) and of New York University (MSEE).


John Dunn

's contributions
  • 11.08.2017
  • 1 Comment(s)
Deriving a rule of thumb
  • 08.31.2017
  • 4 Comment(s)
Static has more than one definition
  • 08.14.2017
  • 19 Comment(s)
The weed-eater circuit
  • 07.27.2017
  • 3 Comment(s)
Vertical antenna capacitance
  • 06.27.2017
PIN diode drive
  • 09.27.2016
  • LED bulbs can bring heat
  • I haven't tested any halogen bulbs in this way, but I guess I will do that. In the meantime though, the issue did arise in response to a different posting. Roger's comments there are very much worth taking note of. Please see the following URL: http://licn.typepad.com/my_weblog/2017/11/another-light-bulb-issue-john-dunn-consultant-ambertec-pe-pc.html
  • 10.31.2017
  • Crystal series and parallel resonances
  • Crystals being used as clock oscillator elements can really cause problems when the exhibit spurious modes. One case in particular is described at: http://licn.typepad.com/my_weblog/2010/12/quartz-crystal-spurious-modes-john-dunn-consutant-ambertec-pe-pc.html
  • 10.24.2017
  • An overlay transistor cautionary tale
  • I never looked into it. I was using the 2N3866 and 2N3375 on the recommendation of older members of the engineering department and they worked. When one day I tried to use a 2N2219 and my RF (10 kHz to 40 MHz) circuit failed to perform, going to the 2N3866 made it work which was as deep as I ever got into the question.
  • 09.12.2017
  • Sziklai transistors: What’s that?
  • Just one caution though. You should include a shunt resistance across the base to emitter junction of Q2 to make sure that Q2 will really go to cut-off when Q1 does.
  • 09.06.2017
  • Beware the TO-220
  • Wasn't there a similar issue with the "TO-3" package? There were so many different versions of that package, your head would spin trying to sort them out. Eventually that package designation number was dropped at least by some companies and today, the 2N3055 as offered by ON Semiconductor calls out the package as "TO-204AA".
  • 08.31.2017
  • Static has more than one definition
  • Of course, dimensional tolerances are key and bent leads can't be very well controlled for that. However, if you don't have to bend anything, if every part simply fits into its proper physical place as shown on the right, you can be pretty well assured there won't be that air gap.
  • 08.22.2017
  • VPN: Proceed with caution
  • Brian, nowhere in your essay to I see a definition of "VPN". I don't know that acronym stands for and so I have very little idea of what you're warning us about.
  • 08.14.2017
  • The weed-eater circuit
  • I just did a Multisim simulation of this circuit using a 2N2222 as the NPN and a 2N2904 as the PNP. The calculated PNP collector voltage emerged as +6.711 volts versus the +6.74 volts shown above. This illustrates the need for making proper assumptions and not getting led astray. The NPN isn't cut off.