Return-Path: Received: (qmail 27289 invoked from network); 13 Nov 2002 14:33:50 -0000 Received: from warrior.services.quay.plus.net (212.159.14.227) by mailstore with SMTP; 13 Nov 2002 14:33:50 -0000 Received: (qmail 3874 invoked from network); 13 Nov 2002 14:34:55 -0000 X-MSMail-Priority: High Received: from post.thorcom.com (193.82.116.70) by warrior.services.quay.plus.net with SMTP; 13 Nov 2002 14:34:54 -0000 X-MimeOLE: Produced By Microsoft MimeOLE V6.00.2800.1106 X-SQ: A Received: from majordom by post.thorcom.com with local (Exim 4.10) id 18Byaq-0005n2-00 for rsgb_lf_group-outgoing@blacksheep.org; Wed, 13 Nov 2002 14:34:12 +0000 Received: from [212.1.130.1] (helo=smtp-1.visp.telinco.net) by post.thorcom.com with esmtp (Exim 4.10) id 18Byaq-0005mt-00 for rsgb_lf_group@blacksheep.org; Wed, 13 Nov 2002 14:34:12 +0000 Received: from [212.1.148.249] (helo=standalone) by smtp-1.visp.telinco.net with smtp (Exim 3.32 #1) id 18ByTv-0003qQ-00 for rsgb_lf_group@blacksheep.org; Wed, 13 Nov 2002 14:27:03 +0000 Received: by localhost with Microsoft MAPI; Wed, 13 Nov 2002 14:32:42 -0000 Message-ID: <01C28B21.86353210.g4jnt@thersgb.net> From: "Andy talbot" To: rsgb_lf_group@blacksheep.org Date: Wed, 13 Nov 2002 14:32:38 -0000 Importance: high X-Priority: 1 X-Mailer: Microsoft Internet E-mail/MAPI - 8.0.0.4211 MIME-Version: 1.0 Subject: LF: RE: Tuesday's riddle (part 2) Content-Type: text/plain; charset=us-ascii; format=flowed Content-Transfer-Encoding: 8bit X-Spam-Status: No, hits=0.9 required=5.0tests=SPAM_PHRASE_01_02,X_PRIORITY_HIGHversion=2.42 Sender: Precedence: bulk Reply-To: rsgb_lf_group@blacksheep.org X-Listname: rsgb_lf_group I didn't get anything like that, but the negative voltage generator has a pronounced threshold as the device starts to avalanche. I wonder if you are getting an effect caused by the capacitive loading of the scope probe coupled with, perhaps, a negative resistance region over the few mV close to avalanche start. Again a guess. Steve's memory of Bob Pease's explanation is a bit unexpected, I wouldn't have thought a reverse biassed junction would generate light. After all, LEDs are forward biassed in operation. Another explanation that someone came up with is that the avalanche generates noise (it certainly does, noise diodes are just RF diodes with reverse breakdown) and that this noise is then being rectified in the C-B junction to give the -ve voltage. I still wonder if it could be due to energetic electrons hitting the base junction and passing though the thin layer, then building up a charge on the reverse biassed C-B junction. Or perhaps a combination of all three ! Andy G4JNT -----Original Message----- From: Rik Strobbe [SMTP:rik.strobbe@fys.kuleuven.ac.be] Sent: 2002/11/13 12:35 To: rsgb_lf_group@blacksheep.org Subject: LF: Tuesday's riddle (part 2) Hello Marcus, very interesting. I did the experiment with a BC547c and as Andy I got a negative voltage. While playing with it I reduced the voltage to +/- 5V and saw an even more interesting effect, over a range of a few 10mV I got a nice sawtooth signal. I wonder if someone can reproduce it ... 73, Rik ON7YD At 14:58 11/11/2002 -0500, you wrote: >Hi group, > >this little experiment was pointed out to me by Ralph, DL2NDO a few years ago: > >You need an ordinary NPN transistor (eg. 2N2222), a 9V battery, a 1k >resistor and a voltmeter. Connect the negative battery terminal to the >base and the positive to the emitter, via the resistor. Now predict the >voltage drop between collector and base. Can't be too hard... > >Then measure it - you'll be surprised. Any explanations? We finally ended >up opening the poor transistor's case. > >Have fun >Markus, DF6NM << File: ATT00000.htm >>