ECL: Why'd they use negative voltages?
in [Design]
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From: Joel Koltner on 7 Jun 2010 19:56 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...) ---Joel
From: Jim Thompson on 7 Jun 2010 20:01 On Mon, 7 Jun 2010 16:56:24 -0700, "Joel Koltner" <zapwireDASHgroups(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...) > >---Joel Noise immunity is better with 0/-5.2V I was there when they (Narud, Seelbach, Philips, et al) did that. ...Jim Thompson -- | James E.Thompson, CTO | mens | | Analog Innovations, Inc. | et | | Analog/Mixed-Signal ASIC's and Discrete Systems | manus | | Phoenix, Arizona 85048 Skype: Contacts Only | | | Voice:(480)460-2350 Fax: Available upon request | Brass Rat | | E-mail Icon at http://www.analog-innovations.com | 1962 | The only thing bipartisan in this country is hypocrisy
From: Joerg on 7 Jun 2010 20:16 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 > 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...) > As Jim said, noise immunity. But also from itself. The upper transistors are the most prone to generate transients in ECL, so it helps if their collectors tie right into chassis. In the old days 4-6 layer boards were unheard of. All you had was 2-layer phenolic, and only if you were lucky. Nowadays that's not an issue anymore because the +5V plane in a PECL scenario is just about as good an RF sink as the ground plane. Why 5.2V I don't know but 6.3V is not an arbitrary voltage, just like 12.6V isn't. That fit the typical car battery voltages just right. So you could hang the filaments straight onto the battery voltage and only had to generate the plate voltages. That was initially done with a mechanical switcher where the "buzzer cartridge" would wear out once in a while. -- Regards, Joerg http://www.analogconsultants.com/ "gmail" domain blocked because of excessive spam. Use another domain or send PM.
From: dagmargoodboat on 7 Jun 2010 20:21 On Jun 7, 7:01 pm, Jim Thompson <To-Email-Use-The-Envelope-I...(a)On-My- Web-Site.com> wrote: > On Mon, 7 Jun 2010 16:56:24 -0700, "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...) > > >---Joel > > Noise immunity is better with 0/-5.2V More specifically, the output's Vcc rejection = 0 (the driver's collector resistors ferry Vcc noise straight-thru). Or did you mean something else, another gotcha? > The only thing bipartisan in this country is hypocrisy Hypocrisy may be bipartisan, but the two camps--socialists vs: free market--are critically different, and not even totally defined by party. GWB spent like crazy. Ahhh, those were the good old days, of fiscal prudence... -- Cheers, James Arthur
From: Joel Koltner on 7 Jun 2010 20:25
"Jim Thompson" <To-Email-Use-The-Envelope-Icon(a)On-My-Web-Site.com> wrote in message news:ot1r06hc3e8adqh07qc8ng6un6ftm2u68q(a)4ax.com... > I was there when they (Narud, Seelbach, Philips, et al) did that. Was the whole idea (just keep the transistors operating in their linear regions rather than saturated or cut-off -- sacrificing power consumprtion for speed) pretty much self-evident to everyone at the time, and it was just a question of convincing enough people of the viability/marketability of the technology so as to get the money for funding all the development -- or was it instead a pretty novel idea, that few people had really thought about and developed up until that point? Thanks, ---Joel |