Error in 1N34 Spice Model?

Discussion in 'Feedback and Suggestions' started by CDRIVE, Jan 21, 2011.

  1. CDRIVE

    Thread Starter Senior Member

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  2. SgtWookie

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    Microcode Engineerings' model for the 1N34 specifies VJ=.75

    *1N34 MCE
    *60V 85mA Ge Signal Diode pkg:DIODE0.4 1,2
    .MODEL 1N34 D(IS=200P RS=84M N=2.19 BV=60 IBV=15U
    + CJO=4.82P VJ=.75 M=.333 TT=144N)
     
  3. CDRIVE

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    Thanks for this Sarge. I've been finding similar data elsewhere and that's my problem. This is a Germanium device, and like its Transistor cousins, had a Vj (Base Emitter junction) of ~.3V. My goodness, I worked with Germanium devices for years prior to Silcon displacing them. Nasty, leaky buggers that they were!

    I have a storage bay that has become so cluttered over the years that I can't get more than a few feet inside it. I'm going to be doing a major cleaning in there soon and I will grab a few 1N34's and other old Germanium Transistors to bench test. I'll post my results when I get enough courage up to face that bay. I only hope that when I do the bench test I don't have a "What the h_ll" moment. If I do, it won't be my first! :D
     
  4. CDRIVE

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    Sarge, I just tested an unknown (unmarked) diode that I believe to be Ge and it drops .5V. Being unmarked, this test doesn't mean much though.
     
  5. SgtWookie

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    At what current did you test it?
    I can get under 0.5v drop on a 1N4148 diode if current is only 0.1mA. 10uA is around 0.38v.

    Yeah, I know those point-contact Germaniums were leaky. Fun though. ;)

    There was a poster awhile back that had problems with an ancient HP tube-based power supply that used a germanium TO3 power transistor - when's the last time you saw one of those? :eek: I suggested that he just replace it with a more modern silicon transistor with similar ratings, as it really wasn't going to make a big difference in the output anyway.
     
  6. CDRIVE

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    Well, I've never measured the short circuit current of my DMM (Diode Test), but it puts out enough current to brightly light a red LED. So for sure this unknown Diode is getting at least a few mA.
    Do you mean that you don't have any test equipment in your shop that uses them? :D I have an old Kepco 0-40V@5A (rack mount) power supply on my bench that's been working for me since about 1968. Not sure about the low current stages but the outputs are either (Ge) TO3s or the (Ge) power transistor case described below.

    When I tunnel into my storage bay I fully expect to find a box full of (Ge) power transistors, including TO3s. I forget their package name, but I also have (Ge) power transistors that look like Flying Saucers. They're stud mounted and predate PCB mounting- because the Emitter & Base leads terminate in an eyelet for point to point wiring. These leads are also about 12AWG. They were made by Motorola (Mil Spec) and were used in a 28VDC to 120V/400VDC plug-in inverter when DOD replaced the ARC-34's Dynamotor with it. Come to think of it, I have a couple of those old Dynamotors and a brand new (old stock) replacement inverter. Black crinkle paint was the the rage back then.:)
     
  7. CDRIVE

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    Here's a wiki link that has a chart near the bottom of the page that shows typical VJE values for Silicon, Germanium, GaAs Transistors.

    http://en.wikipedia.org/wiki/Transistor

    I knew I wasn't going crazy!:D

    And here's a snip from this wiki Diode page where Ge Diodes are referenced.
    http://en.wikipedia.org/wiki/Diode

    As the potential difference is increased above an arbitrarily defined “cut-in voltage” or “on-voltage” or “diode forward voltage drop (Vd)”, the diode current becomes appreciable (the level of current considered “appreciable” and the value of cut-in voltage depends on the application), and the diode presents a very low resistance. The current–voltage curve is exponential. In a normal silicon diode at rated currents, the arbitrary “cut-in” voltage is defined as 0.6 to 0.7 volts. The value is different for other diode types — Schottky diodes can be rated as low as 0.2 V, Germanium diodes 0.25 to 0.3 V, and red or blue light-emitting diodes (LEDs) can have values of 1.4 V and 4.0 V respectively.
    At higher currents the forward voltage drop of the diode increases. A drop of 1 V to 1.5 V is typical at full rated current for power diodes
     
  8. SgtWookie

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    Here's an interesting page:
    http://www.lessmiths.com/~kjsmith/crystal/dtest.shtml
    1N34 diodes were a part of the fellow's tests.

    I quickly checked the diode test current of a couple of my "El Cheapo" Harbor Freight DMM's; roughly 1.2mA. According to the above page, expected Vf for that current would be around 0.25v-0.3v. I don't know where or how MCE came up with the VJ=.75 specification.

    Just to point out - I'm not arguing with you; just trying to find out the "whys" and "whats" of how this all came about.
     
    Last edited: Jan 26, 2011
  9. CDRIVE

    Thread Starter Senior Member

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    I wasn't looking for an argument either, I was seeking confirmation that I wasn't becoming senile. Some memories do get blurred over time. I'm afraid that it's not just MCE that shows this discrepancy, as I've found the same contradiction in other data sheets. It's almost as though history was somehow re-written since the day when pdfs didn't exist and data was gleaned from the manufacturer's data manuals, which covered hundreds of their models.

    BTW, I also tested my Fluke and Tenma DMM's and they deliver about the same current as your "El Cheapos". As I said though; the diode I tested is unmarked. Just because the case is glass doesn't dictate what family the diode is in.

    Regarding your link: Mr. Smith's is certainly meticulous. I simply loved the beautiful wooden bases he used for his Vac Tube fixtures. They remind me of how things used to be done back in the day. As a Young'n all my circuits and home brew motors were mounted on nicely beveled wood bases. I never cleaned the mess left in my Dad's shop, which did not please him!

    Thanks for your participation in this study.
    Chris
     
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