henry@utzoo.uucp (Henry Spencer) (11/30/89)
In article <24473@cup.portal.com> ISW@cup.portal.com (Isaac S Wingfield) writes: >...we concluded that germanium diode specs >were all kind of loose, and it was possible to duplicate (or even better) >all specs *except* FCD using silicon, and that's what nearly everybody >was doing! The ITT devices came in at 0.3V, and everything was fine. I was sort of curious about this, and ran some tests on the 1N34s I've got in my parts box at home. They are from Rockwell, I think -- at least the tiny symbol on the side looks like the Rockwell logo! I *think* these are germanium; the current-vs-voltage curve does start to break at 0.3V. What startled me a bit was how gradual the rise was after that; within the limits of my simple measuring setup, it looked like a near-linear rise at about 1mA/100mV, whereas the one for a 1N4148 is nearly vertical at circa 0.6V. Is this normal for germanium, or have I got something funny like silicon pretending to be germanium? -- That's not a joke, that's | Henry Spencer at U of Toronto Zoology NASA. -Nick Szabo | uunet!attcan!utzoo!henry henry@zoo.toronto.edu
ISW@cup.portal.com (Isaac S Wingfield) (12/01/89)
(I wrote:) >>...we concluded that germanium diode specs >>were all kind of loose, and it was possible to duplicate (or even better) >>all specs *except* FCD using silicon, and that's what nearly everybody >>was doing! The ITT devices came in at 0.3V, and everything was fine. (And Henry Spencer wrote:) >I was sort of curious about this, and ran some tests on the 1N34s I've >got in my parts box at home. They are from Rockwell, I think -- at least >the tiny symbol on the side looks like the Rockwell logo! I *think* these >are germanium; the current-vs-voltage curve does start to break at 0.3V. >What startled me a bit was how gradual the rise was after that; within >the limits of my simple measuring setup, it looked like a near-linear rise >at about 1mA/100mV, whereas the one for a 1N4148 is nearly vertical at >circa 0.6V. Is this normal for germanium, or have I got something funny >like silicon pretending to be germanium? >-- >That's not a joke, that's | Henry Spencer at U of Toronto Zoology >NASA. -Nick Szabo | uunet!attcan!utzoo!henry henry@zoo.toronto.ed u Checking a mid-50's Sylvania reference, they say a 1N34 can have a forward resistance of 200 ohms max. at 1 volt, so your result is not out of line. Sounds to me like you've got the real thing. Gonna build a crystal set? Something way in the back of my mind is saying there is/was some kind of alliance or merger or something concerning Rockwell and ITT. I'm really not sure; just a feeling.... As long as we're still on the subject, someone (sorry, lost the attribution) said it would be easy to tell Si from Ge just by checking the data sheet; I presume they haven't read too many older data sheets, which tended to be a bit sparse by today's standards. Here's *all* Sylvania (the manufacturer) had to say about the 1N34: Description: General Purpose Diode Ambient Temperature Range (deg C): -50 to +75. (All following ratings are specified at 25 C only) Continuous Reverse Working Volts: 60 Recurrent Peak Anode Current (ma): 150 Average Anode Current (ma): 50 Surge Current (ma, 1 sec): 500 Peak Reverse Voltage (Volts min): 75 Forward current at +1V (ma, min): 5 Reverse Current (microamps, min): 30 @ -10V, 500 @ -50V Forward Resistance at +1V (ohms max): 200 Reverse Resistance (ohms min): 333K @ -10V, 100K @ -50V Well, I dunno. About the only clue I get from that as to what kind of diode it is, is *not a very good one*. That's why manufacturers could substitute Silicon (floor sweepings, even) and still satisfy the "spec". Nostalgia time: Early 1N34's were point contact devices packaged in a ceramic tube with screw-on metal end caps (looked like a short fuse). There were construction articles on how to take two of these things apart to get the tungsten cat whiskers, and put both of them *real close together* on one of the germanium crystals to make your own transistor. I never got it to work. Isaac isw@cup.portal.com
henry@utzoo.uucp (Henry Spencer) (12/02/89)
In article <24605@cup.portal.com> ISW@cup.portal.com (Isaac S Wingfield) writes: >Sounds to me like you've got the real thing. Gonna build a crystal set? I've occasionally thought about trying it, but last time I priced a decent variable capacitor I decided it was a bit much for a whim. Someday maybe. I picked up a handful of 1N34s a while ago, for some experiments with battery-backup circuits that wanted a diode with a low forward drop. -- Mars can wait: we've barely | Henry Spencer at U of Toronto Zoology started exploring the Moon. | uunet!attcan!utzoo!henry henry@zoo.toronto.edu