ECL: Why'd they use negative voltages?
in [Design]
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From: Michael A. Terrell on 7 Jun 2010 22:11 D Yuniskis wrote: > > Hi Joel, > > Joel Koltner wrote: > > I realize it was the early '60s and all, but why does ECL generally use > > 0V for VCC and -5.2V for VEE, rather than, oh, say... 5V for VCC and 0V > > You also had a Vbb of around -1.2V (?). Lines were typically terminated > to this. > > > for VEE? Something related to how things were done when toobs ruled? (I > > realize that you can almost always run ECL off of 5V/0V -- and > > apparently this was popular practice at one time?) > > > > And why 5.2V anyway? (Granted, 5.2V is no stranger than 6.3V filament > > transformers, I suppose...) > > Dunno. But, it was fast and ate gobs of power. In the > mid 70's I worked on a processor (i.e., what nowadays > would be a CPU "chip") that drew 100A (MECL III and 10K). > "Bus bars" for power were 3/4" square copper shafts. > Instruction cycle time was 8ns. By comparison, I think a > 7404 (inverter) takes *7* ns just to change the state of > its output. > > If you "slipped" when pulling/installing a chip, the legs > would vaporize before the power supply would even hiccup. > (needless to say, you removed all jewelry -- belt buckles, > eye glasses, rings, etc. -- when working on it) You should have seen one of the first generation NTSC effects generator called the 'SqueezeZoom' It had a linear 5 V 1000 A linear power supply with a 208 three phase input. -- Anyone wanting to run for any political office in the US should have to have a DD214, and a honorable discharge.
From: Bill Sloman on 7 Jun 2010 22:12 On Jun 8, 1:56 am, "Joel Koltner" <zapwireDASHgro...(a)yahoo.com> wrote: > I realize it was the early '60s and all, but why does ECL generally use 0V for > VCC and -5.2V for VEE, rather than, oh, say... 5V for VCC and 0V for VEE? > Something related to how things were done when toobs ruled? (I realize that > you can almost always run ECL off of 5V/0V -- and apparently this was popular > practice at one time?) > > And why 5.2V anyway? (Granted, 5.2V is no stranger than 6.3V filament > transformers, I suppose...) ECL uses NPN emitter follower transistors to buffer the output signal. If you bias ECL between 0V and 5V (PECL)and short an output to ground, you can draw quite a lot current from the small and rather fragile output transistors, with a serious risk of blowing them up. Bias ECL between 0V and -5.2V (or whatever - 100K ECL used -4.5V) and shorting the output to ground merely reveres biases the base-emitter junction, and nothing blows up. Hewlett-Packard used ECL biased between )v and 5V in their laser- interferometer positioning system, and when I complained about the risk to one of the HP reps, he did admit that most of their repair work on duff laser interferometers was replacing ECL chips with dead outputs. Admittedly, they had made life riskier by putting a differential ECL signal pair on the inner and outer of a singel regular coaxial connector, which left a biggish chunk of metal that service engineers could brush with the ground lead on their scope probe. Trust Jim-out-of-touch-with=reality-Thompson to be unaware of this. -- Bill Sloman, Nijmegen
From: D Yuniskis on 7 Jun 2010 22:22 Hi Joel, Joel Koltner wrote: > "Vladimir Vassilevsky" <nospam(a)nowhere.com> wrote in message > news:26GdnUsFmvX4PZDRnZ2dnUVZ_vadnZ2d(a)giganews.com... >> Joel Koltner wrote: >>> --> http://sound.westhost.com/project117.htm (a 1500W audio >>> amplifier, "It is capable of destroying any loudspeaker connected to >>> it, regardless of claimed power rating.") :-) >> Pathetic :))))) >> Here is 10kW audio amplifier. Yes, 10kW true RMS sustained sinusoidal >> power. > > One has to wonder what sort of speaker systems are used with such an > amplifier (10kW) if 1.5kW is purportedly enough to kill any individual > speaker -- must be quite the array! My "home speakers" could suck down 600W (each). They were 4 ft wide, 3.5 deep and 6 ft tall. They weighed 1200 pounds. The neighbors would visit and ask, "And how are the *children* today?" <frown> > Ah, only a 200Hz frequency limit though: > http://caraudiomag.com/articles/kicker-wx100001-warhorse-review-amplifier > -- and I bet even there the distortion specs aren't that great? > > Still, a very cool accomplishment...
From: D Yuniskis on 7 Jun 2010 22:28 Hi Michael, Michael A. Terrell wrote: > D Yuniskis wrote: >> Hi Joel, >> >> Joel Koltner wrote: >>> I realize it was the early '60s and all, but why does ECL generally use >>> 0V for VCC and -5.2V for VEE, rather than, oh, say... 5V for VCC and 0V >> You also had a Vbb of around -1.2V (?). Lines were typically terminated >> to this. >> >>> for VEE? Something related to how things were done when toobs ruled? (I >>> realize that you can almost always run ECL off of 5V/0V -- and >>> apparently this was popular practice at one time?) >>> >>> And why 5.2V anyway? (Granted, 5.2V is no stranger than 6.3V filament >>> transformers, I suppose...) >> Dunno. But, it was fast and ate gobs of power. In the >> mid 70's I worked on a processor (i.e., what nowadays >> would be a CPU "chip") that drew 100A (MECL III and 10K). >> "Bus bars" for power were 3/4" square copper shafts. >> Instruction cycle time was 8ns. By comparison, I think a >> 7404 (inverter) takes *7* ns just to change the state of >> its output. >> >> If you "slipped" when pulling/installing a chip, the legs >> would vaporize before the power supply would even hiccup. >> (needless to say, you removed all jewelry -- belt buckles, >> eye glasses, rings, etc. -- when working on it) > > You should have seen one of the first generation NTSC effects > generator called the 'SqueezeZoom' It had a linear 5 V 1000 A linear > power supply with a 208 three phase input. Yikes! I have no idea what the entire "tester" consumed (my responsibility was primarily the CPU). We had a dedicated service installed *just* for it, though. Power cord took two of us to plug in (and twist-lock)... some idiot mounted the outlet at eye level (not very smart when you're lifting all that copper/rubber and trying to mate the things). (sigh) As I said, disappointing to see such brute force used. Even the UUT connection was by way of a third horsepower motor driven "connector engagement system". Though I guess it would be hard to do it otherwise (today you could probably integrate much of the electronics and get some huge wins from just reducing the size of everything)
From: Vladimir Vassilevsky on 7 Jun 2010 22:43
D Yuniskis wrote: > Hi Joel, > > Joel Koltner wrote: > >> "Vladimir Vassilevsky" <nospam(a)nowhere.com> wrote in message >> news:26GdnUsFmvX4PZDRnZ2dnUVZ_vadnZ2d(a)giganews.com... >> >>> Joel Koltner wrote: >>> >>>> --> http://sound.westhost.com/project117.htm (a 1500W audio >>>> amplifier, "It is capable of destroying any loudspeaker connected to >>>> it, regardless of claimed power rating.") :-) >>> >>> Pathetic :))))) >>> Here is 10kW audio amplifier. Yes, 10kW true RMS sustained sinusoidal >>> power. >> >> >> One has to wonder what sort of speaker systems are used with such an >> amplifier (10kW) if 1.5kW is purportedly enough to kill any individual >> speaker -- must be quite the array! The recomended system is 4 x 18' woofers. > My "home speakers" could suck down 600W (each). They were 4 ft > wide, 3.5 deep and 6 ft tall. They weighed 1200 pounds. The > neighbors would visit and ask, "And how are the *children* today?" I have some doubts. The actual impedance of the speakers is usually much higher then rated resistance. A good big loudspeaker can dissipate few hundred W of sustained active power. The mechanical damage of the speakers (due to the material fatigue) is big problem at those power levels also. Vladimir Vassilevsky DSP and Mixed Signal Design Consultant http://www.abvolt.com |