Ohm's Law Problem
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From: Jim Thompson on 16 Feb 2010 12:25 On Tue, 16 Feb 2010 09:22:53 -0800, Joerg <invalid(a)invalid.invalid> wrote: >Jim Thompson wrote: >> On Tue, 16 Feb 2010 09:10:06 -0800, Joerg <invalid(a)invalid.invalid> >> wrote: >> >>> Jon Kirwan wrote: >>>> On Mon, 15 Feb 2010 13:29:30 -0800, Joerg >>>> <invalid(a)invalid.invalid> wrote: >>>> >>>>> <snip> >>>>> It's much more important to >>>>> experiment, experiment, experiment, get a "feel" for what works, _then_ >>>>> dive into the theory. Not the other way around. Just my 2 cents. >>>> It's hard for most of us to get a feel for what works without >>>> first having some idea of what to expect. Theory is primary >>>> to interpreting and understanding experimental result. >>>> >>>> What isn't known through theory defines the word 'random.' >>>> >>> That would be the professor's thought process. To us back then things we >>> didn't understand were not random at all. For example, you simply "knew" >>> that the Q of a power matching network had to be at least 10 or you'd >>> get into EMI troubles. Or that grid-bias tube stages were way more >>> stable by nature. Or that certain modes of operation in a transistor >>> could lead to a phssst ... *BANG* (later I learned about the concept of >>> a SOA), and so on. >>> >>> If it was all random we'd have had much more failing parts and homebrew >>> devices, but we didn't. >> >> "phssst ... *BANG*" - Joerg "Failure Noise du Jour" Schulze-Clewing >> ;-) >> > >Actually back then I did more with tubes, because they were essentially >free. Then the failures sounded more like this: > >... tck ....... tck .... tck .. tck .. t .. t ..TICK ... pheeeooouu ... >*POF* ... followed by the sound of falling glass pieces. I've made plates sag, but never blew any glass. ...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 | I love to cook with wine. Sometimes I even put it in the food.
From: Charlie E. on 16 Feb 2010 13:07 On Mon, 15 Feb 2010 20:36:31 -0500, Bitrex <bitrex(a)de.lete.earthlink.net> wrote: >Joerg wrote: >> Joel Koltner wrote: >>> "Jim Thompson" <To-Email-Use-The-Envelope-Icon(a)My-Web-Site.com> wrote >>> in message news:11sin51vdubl64ouhcgn3b2omf36q111in(a)4ax.com... >>>> Everyone is making it too difficult. Just write it down in sequence, >>>> the answer falls right out... >>>> http://analog-innovations.com/SED/OhmsLaw_SED_JustWriteItDown.pdf >>> >> >> Ohm's law? I thought that had been repealed ... :-) >> >> >>> That's the same as what I ended up doing (in the later part of my >>> post), except that you use "V3/100" rather than just "I" for the >>> current in the lowest resistor. :-) >>> >>>> At MIT, I was spared (*) from Guillemin's obtuseness, I had Harry B. >>>> Lee for passive circuit analysis ;-) >>> >>> I had a guy who was a pretty talented teacher (he'd won a couple >>> awards for it, and I found him quite understandable), although he had >>> little if any real-world design experience. >>> >>> I'd read some of Guillemin's book, and while I think the guy was >>> pretty darned sharp, I disagree with his notion that you have to have >>> an incredibly thorough understanding of network analysis down pat >>> before you can get useful circuit design or analysis done. ... >> >> >> Sadly, that's the kind of notion that drives potential EE candidates >> away, at least from analog. And now we have a serious shortage of those. >> They think they have to be a rocket scientists to be able to thrive and >> make money in analog. Which is wrong. I learned the majority of my >> skills by "winging it". IOW I built RF stuff before I knew squat about >> any of that. And it actually worked, some still does. >> >> Note to potential candidates: If an author or professor says something >> like what must have been stipulated in this book, that you must be a top >> notch network analyst, do not listen. It's much more important to >> experiment, experiment, experiment, get a "feel" for what works, _then_ >> dive into the theory. Not the other way around. Just my 2 cents. >> >> Whew. Now I feel better ... >> > >Here's a question I'd like an honest answer to: I've studied analog >design for a long time as a hobby, but I was never able to attend a >university program of study for it during my 20s due to a series of >illnesses, and having to work hard when I was well enough to stay >afloat. I'm now 30, and I'm fortunate to currently be in a stable >enough situation to attempt a degree. I love EE, and would like >to study it formally, but if the future is truly as bleak for US >engineers (particularly ones who who will be at least 35 before they >land their first job) I should probably really let that sink in before >starting. Bitrex, Do you have a degree presently? Did you get another degree back in the deeps of time? If so, then go for a masters in EE. Easier, and more fun! Charlie
From: Joerg on 16 Feb 2010 14:38 Jim Thompson wrote: > On Tue, 16 Feb 2010 09:22:53 -0800, Joerg <invalid(a)invalid.invalid> > wrote: > >> Jim Thompson wrote: >>> On Tue, 16 Feb 2010 09:10:06 -0800, Joerg <invalid(a)invalid.invalid> >>> wrote: >>> >>>> Jon Kirwan wrote: >>>>> On Mon, 15 Feb 2010 13:29:30 -0800, Joerg >>>>> <invalid(a)invalid.invalid> wrote: >>>>> >>>>>> <snip> >>>>>> It's much more important to >>>>>> experiment, experiment, experiment, get a "feel" for what works, _then_ >>>>>> dive into the theory. Not the other way around. Just my 2 cents. >>>>> It's hard for most of us to get a feel for what works without >>>>> first having some idea of what to expect. Theory is primary >>>>> to interpreting and understanding experimental result. >>>>> >>>>> What isn't known through theory defines the word 'random.' >>>>> >>>> That would be the professor's thought process. To us back then things we >>>> didn't understand were not random at all. For example, you simply "knew" >>>> that the Q of a power matching network had to be at least 10 or you'd >>>> get into EMI troubles. Or that grid-bias tube stages were way more >>>> stable by nature. Or that certain modes of operation in a transistor >>>> could lead to a phssst ... *BANG* (later I learned about the concept of >>>> a SOA), and so on. >>>> >>>> If it was all random we'd have had much more failing parts and homebrew >>>> devices, but we didn't. >>> "phssst ... *BANG*" - Joerg "Failure Noise du Jour" Schulze-Clewing >>> ;-) >>> >> Actually back then I did more with tubes, because they were essentially >> free. Then the failures sounded more like this: >> >> ... tck ....... tck .... tck .. tck .. t .. t ..TICK ... pheeeooouu ... >> *POF* ... followed by the sound of falling glass pieces. > > I've made plates sag, but never blew any glass. > That is because you were not a ham radio operator on a tight budget. We had glass turning mildly liquid, being sucked in and ending up snug on the plates. That was the time to turn off the rig. A few seconds more in transmit and there'd be a loud bang. -- Regards, Joerg http://www.analogconsultants.com/ "gmail" domain blocked because of excessive spam. Use another domain or send PM.
From: Jim Thompson on 16 Feb 2010 14:54 On Tue, 16 Feb 2010 11:38:45 -0800, Joerg <invalid(a)invalid.invalid> wrote: >Jim Thompson wrote: >> On Tue, 16 Feb 2010 09:22:53 -0800, Joerg <invalid(a)invalid.invalid> >> wrote: >> >>> Jim Thompson wrote: >>>> On Tue, 16 Feb 2010 09:10:06 -0800, Joerg <invalid(a)invalid.invalid> >>>> wrote: >>>> >>>>> Jon Kirwan wrote: >>>>>> On Mon, 15 Feb 2010 13:29:30 -0800, Joerg >>>>>> <invalid(a)invalid.invalid> wrote: >>>>>> >>>>>>> <snip> >>>>>>> It's much more important to >>>>>>> experiment, experiment, experiment, get a "feel" for what works, _then_ >>>>>>> dive into the theory. Not the other way around. Just my 2 cents. >>>>>> It's hard for most of us to get a feel for what works without >>>>>> first having some idea of what to expect. Theory is primary >>>>>> to interpreting and understanding experimental result. >>>>>> >>>>>> What isn't known through theory defines the word 'random.' >>>>>> >>>>> That would be the professor's thought process. To us back then things we >>>>> didn't understand were not random at all. For example, you simply "knew" >>>>> that the Q of a power matching network had to be at least 10 or you'd >>>>> get into EMI troubles. Or that grid-bias tube stages were way more >>>>> stable by nature. Or that certain modes of operation in a transistor >>>>> could lead to a phssst ... *BANG* (later I learned about the concept of >>>>> a SOA), and so on. >>>>> >>>>> If it was all random we'd have had much more failing parts and homebrew >>>>> devices, but we didn't. >>>> "phssst ... *BANG*" - Joerg "Failure Noise du Jour" Schulze-Clewing >>>> ;-) >>>> >>> Actually back then I did more with tubes, because they were essentially >>> free. Then the failures sounded more like this: >>> >>> ... tck ....... tck .... tck .. tck .. t .. t ..TICK ... pheeeooouu ... >>> *POF* ... followed by the sound of falling glass pieces. >> >> I've made plates sag, but never blew any glass. >> > >That is because you were not a ham radio operator on a tight budget. We >had glass turning mildly liquid, being sucked in and ending up snug on >the plates. That was the time to turn off the rig. A few seconds more in >transmit and there'd be a loud bang. I knew to back off on the bias when the plates turned cherry red ;-) ...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 | I love to cook with wine. Sometimes I even put it in the food.
From: Joerg on 16 Feb 2010 15:01
Jim Thompson wrote: > On Tue, 16 Feb 2010 11:38:45 -0800, Joerg <invalid(a)invalid.invalid> > wrote: > >> Jim Thompson wrote: >>> On Tue, 16 Feb 2010 09:22:53 -0800, Joerg <invalid(a)invalid.invalid> >>> wrote: >>> >>>> Jim Thompson wrote: >>>>> On Tue, 16 Feb 2010 09:10:06 -0800, Joerg <invalid(a)invalid.invalid> >>>>> wrote: >>>>> >>>>>> Jon Kirwan wrote: >>>>>>> On Mon, 15 Feb 2010 13:29:30 -0800, Joerg >>>>>>> <invalid(a)invalid.invalid> wrote: >>>>>>> >>>>>>>> <snip> >>>>>>>> It's much more important to >>>>>>>> experiment, experiment, experiment, get a "feel" for what works, _then_ >>>>>>>> dive into the theory. Not the other way around. Just my 2 cents. >>>>>>> It's hard for most of us to get a feel for what works without >>>>>>> first having some idea of what to expect. Theory is primary >>>>>>> to interpreting and understanding experimental result. >>>>>>> >>>>>>> What isn't known through theory defines the word 'random.' >>>>>>> >>>>>> That would be the professor's thought process. To us back then things we >>>>>> didn't understand were not random at all. For example, you simply "knew" >>>>>> that the Q of a power matching network had to be at least 10 or you'd >>>>>> get into EMI troubles. Or that grid-bias tube stages were way more >>>>>> stable by nature. Or that certain modes of operation in a transistor >>>>>> could lead to a phssst ... *BANG* (later I learned about the concept of >>>>>> a SOA), and so on. >>>>>> >>>>>> If it was all random we'd have had much more failing parts and homebrew >>>>>> devices, but we didn't. >>>>> "phssst ... *BANG*" - Joerg "Failure Noise du Jour" Schulze-Clewing >>>>> ;-) >>>>> >>>> Actually back then I did more with tubes, because they were essentially >>>> free. Then the failures sounded more like this: >>>> >>>> ... tck ....... tck .... tck .. tck .. t .. t ..TICK ... pheeeooouu ... >>>> *POF* ... followed by the sound of falling glass pieces. >>> I've made plates sag, but never blew any glass. >>> >> That is because you were not a ham radio operator on a tight budget. We >> had glass turning mildly liquid, being sucked in and ending up snug on >> the plates. That was the time to turn off the rig. A few seconds more in >> transmit and there'd be a loud bang. > > I knew to back off on the bias when the plates turned cherry red ;-) > Had nothing to do with bias. We had "dynamic bias", meaning bias was only applied when a drive signal was detected by a Ge diode and transistor. Else the tube consumption per year would reach fiscally unfathomable levels, at least for a student. Problem was that we squeezed them out real hard. For example an amp with five H-deflection tubes for color TVs delivering a sustained 1200 watts of raw RF output power. No joke, this was measured with a calibrated Bird wattmeter and was legit back then in Germany. It blew up my antennas numerous times. The loudest bang was a balun where the T200 Amidon core was literally gone afterwards. Shoulda stacked two cores but only had the money for one ... -- Regards, Joerg http://www.analogconsultants.com/ "gmail" domain blocked because of excessive spam. Use another domain or send PM. |