You da man!
pc motherboard grounds
Started by ●August 25, 2012
Reply by ●August 26, 20122012-08-26
Reply by ●August 26, 20122012-08-26
John Larkin wrote:> > You *don't* understand my circuit!I wish I did. Whether he does or not, would you mind describing it? -- Reply in group, but if emailing add one more zero, and remove the last word.
Reply by ●August 27, 20122012-08-27
On Sun, 26 Aug 2012 22:53:35 -0400, "Tom Del Rosso" <td_03@verizon.net.invalid> wrote:> >John Larkin wrote: >> >> You *don't* understand my circuit! > >I wish I did. Whether he does or not, would you mind describing it?This one? https://dl.dropbox.com/u/53724080/Circuits/Isrc_Ib_2.JPG U1 and the p-fet are a slow but precise closed-loop current source. It's cascoded into the fast PNP transistor below, which gives us low output capacitance. R3 allows the PNP emitter to move a bit and reduce Early effect. R4 keeps the PNP from oscillating. The big DC error becomes the base current of the PNP. RF PNPs tend to have have low betas, so we lose some of our precise current to the base, and that changes with tempearture. So we dump the base current into U2, and the resulting signal (drop across R2) increases the effective reference voltage to the upper current source, increasing the emitter current, almost canceling the base current error. R2=R1 gets us close enough. The base current cancellation is a positive feedback loop, but the gain is low, basically 1/beta, so it's stable. Jim is on record as not liking this. He won't say why. -- John Larkin Highland Technology Inc www.highlandtechnology.com jlarkin at highlandtechnology dot com Precision electronic instrumentation Picosecond-resolution Digital Delay and Pulse generators Custom timing and laser controllers Photonics and fiberoptic TTL data links VME analog, thermocouple, LVDT, synchro, tachometer Multichannel arbitrary waveform generators
Reply by ●August 27, 20122012-08-27
On Sun, 26 Aug 2012 20:24:20 -0700, John Larkin <jjlarkin@highNOTlandTHIStechnologyPART.com> wrote:>On Sun, 26 Aug 2012 22:53:35 -0400, "Tom Del Rosso" ><td_03@verizon.net.invalid> wrote: > >> >>John Larkin wrote: >>> >>> You *don't* understand my circuit! >> >>I wish I did. Whether he does or not, would you mind describing it? > >This one? > >https://dl.dropbox.com/u/53724080/Circuits/Isrc_Ib_2.JPG > >U1 and the p-fet are a slow but precise closed-loop current source. >It's cascoded into the fast PNP transistor below, which gives us low >output capacitance. R3 allows the PNP emitter to move a bit and reduce >Early effect. R4 keeps the PNP from oscillating. > >The big DC error becomes the base current of the PNP. RF PNPs tend to >have have low betas, so we lose some of our precise current to the >base, and that changes with tempearture. So we dump the base current >into U2, and the resulting signal (drop across R2) increases the >effective reference voltage to the upper current source, increasing >the emitter current, almost canceling the base current error. > >R2=R1 gets us close enough. The base current cancellation is a >positive feedback loop, but the gain is low, basically 1/beta, so it's >stable. > >Jim is on record as not liking this. He won't say why.Post the circuit WITH VALUES so it can be checked. Otherwise it's a figment of the Napoleonic runt. ...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.
Reply by ●August 27, 20122012-08-27
On Sun, 26 Aug 2012 20:47:48 -0700, Jim Thompson <To-Email-Use-The-Envelope-Icon@On-My-Web-Site.com> wrote:>On Sun, 26 Aug 2012 20:24:20 -0700, John Larkin ><jjlarkin@highNOTlandTHIStechnologyPART.com> wrote: > >>On Sun, 26 Aug 2012 22:53:35 -0400, "Tom Del Rosso" >><td_03@verizon.net.invalid> wrote: >> >>> >>>John Larkin wrote: >>>> >>>> You *don't* understand my circuit! >>> >>>I wish I did. Whether he does or not, would you mind describing it? >> >>This one? >> >>https://dl.dropbox.com/u/53724080/Circuits/Isrc_Ib_2.JPG >> >>U1 and the p-fet are a slow but precise closed-loop current source. >>It's cascoded into the fast PNP transistor below, which gives us low >>output capacitance. R3 allows the PNP emitter to move a bit and reduce >>Early effect. R4 keeps the PNP from oscillating. >> >>The big DC error becomes the base current of the PNP. RF PNPs tend to >>have have low betas, so we lose some of our precise current to the >>base, and that changes with tempearture. So we dump the base current >>into U2, and the resulting signal (drop across R2) increases the >>effective reference voltage to the upper current source, increasing >>the emitter current, almost canceling the base current error. >> >>R2=R1 gets us close enough. The base current cancellation is a >>positive feedback loop, but the gain is low, basically 1/beta, so it's >>stable. >> >>Jim is on record as not liking this. He won't say why. > >Post the circuit WITH VALUES so it can be checked. Otherwise it's a >figment of the Napoleonic runt. > > ...Jim ThompsonWhat you are saying is that you can't decide if it will work unless I show all the values. Which means you can't find suitable values yourself. Which meand you can't understand it. QED. Hint: all the resistor values can be the same. -- John Larkin Highland Technology Inc www.highlandtechnology.com jlarkin at highlandtechnology dot com Precision electronic instrumentation Picosecond-resolution Digital Delay and Pulse generators Custom timing and laser controllers Photonics and fiberoptic TTL data links VME analog, thermocouple, LVDT, synchro, tachometer Multichannel arbitrary waveform generators
Reply by ●August 27, 20122012-08-27
On Sat, 25 Aug 2012 17:44:16 -0700, John Larkin <jjlarkin@highNOTlandTHIStechnologyPART.com> wrote:>On Sat, 25 Aug 2012 15:09:16 -0700, Jim Thompson ><To-Email-Use-The-Envelope-Icon@On-My-Web-Site.com> wrote: > >>On Sat, 25 Aug 2012 10:31:03 -0700, John Larkin >><jjlarkin@highNOTlandTHIStechnologyPART.com> wrote: >> >>>On Sat, 25 Aug 2012 10:14:48 -0700, Jim Thompson >>><To-Email-Use-The-Envelope-Icon@On-My-Web-Site.com> wrote: >>> >>>>On Sat, 25 Aug 2012 10:03:49 -0700, John Larkin >>>><jjlarkin@highNOTlandTHIStechnologyPART.com> wrote: >>>> >>>>>On Sat, 25 Aug 2012 09:40:54 -0700, Jim Thompson >>>>><To-Email-Use-The-Envelope-Icon@On-My-Web-Site.com> wrote: >>>>> >>>>>>On Sat, 25 Aug 2012 09:34:54 -0700, John Larkin >>>>>><jjlarkin@highNOTlandTHIStechnologyPART.com> wrote: >>>>>> >>>>>>> >>>>>>> >>>>>>>The mounting holes on PC motherboards: are they usually connected =to>>>>>>>the PCB ground plane? >>>>>> >>>>>>depends. Are you wearing them like you should ?:-) >>>>>> =09 >>>>>> ...Jim Thompson >>>>> >>>>>You never actually say anything with content any more. You don't =even>>>>>discuss circuits in any intelligent way. You've become a useless old >>>>>hen. >>>> >>>>And your WORKING circuits are WHERE ?:-) >>>> =09 >>>> ...Jim Thompson >>> >>>A few are here: >>> >>>http://www.highlandtechnology.com/index.shtml >>> >>> >>>Any your fast current source is where? You can't do it! >>> >>>I rather liked the mosfet-bipolar cascode with Ib correction, but you >>>didn't. What did you find wrong with it? I mean, aside from the fact >>>that I invented it. Are you claiming that this *won't* work? >>> >>>https://dl.dropbox.com/u/53724080/Circuits/Isrc_Ib_2.JPG >>> >>> >>>But I have a couple of better, cuter circuits by now. Show us your >>>approach, and then I'll post a couple more of mine. >>> >>>You never say anything substantive about electronics lately. You can't >>>invent circuits any more. Go back to sci.electronics.basics where >>>amateurs belong. >> >>Show some LTspice .ASC files that can be checked. Then people will >>believe your claims. >> =09 > >That's silly. If you can't look at a circuit and understand it, and >decide how well it will work, and you need a simulator to do your >thinking for you, then you are an amateur. I wouldn't Spice anything >this simple.=20 > >Good grief, you *don't* understand my circuit!I learned the hard way not to believe in anything without proper part values. Nor do i spice up fragments. ?-)
Reply by ●August 27, 20122012-08-27
On Sun, 26 Aug 2012 12:38:59 -0700, John Larkin <jjlarkin@highNOTlandTHIStechnologyPART.com> wrote:>On Sun, 26 Aug 2012 08:01:35 -0700, Jim Thompson ><To-Email-Use-The-Envelope-Icon@On-My-Web-Site.com> wrote: > >>On Sat, 25 Aug 2012 21:58:02 -0700, John Larkin >><jjlarkin@highNOTlandTHIStechnologyPART.com> wrote: >> >>>On Sat, 25 Aug 2012 19:47:01 -0700, Jim Thompson >>><To-Email-Use-The-Envelope-Icon@On-My-Web-Site.com> wrote: >>> >>>>On Sat, 25 Aug 2012 18:19:02 -0700, John Larkin >>>><jjlarkin@highNOTlandTHIStechnologyPART.com> wrote: >>>> >>[snip] >>>> >>>>WHERE did you SHOW a WORKING circuit ?? You didn't. >>> >>>I've posted a bunch of current source circuits. They all work. >> >>In previous posts you said that the ones you attempted for your 1V/ns >>ramp oscillated?? > >It depends on the PNP transistor and the value of the base resistor. A >BCX71 oscillates at around 80 MHz, and the hotter RF parts much >higher. It has nothing to do with the opamp gain/phase as you >suggested; the oscillation is local to the transistor. 100 ohms in the >base fixes it for pretty much all cases.=20 > >> >>> >>>> >>>>I design sub-nanosecond stuff on-chip all the time, so shove your >>>>snarky crap up your ass. >>>> >>>>You're a shit "designer"... all NO-SHOW. >>>> =09 >>>> ...Jim Thompson >>> >>>So show something of your own. >>> >>>You can't. >> >>Show us the ramp device that _doesn't_ oscillate. > >As noted, the proper base/gate resistor fixes it, as it does for most >emitter-follower type circuits. Not many people appreciate how much >emitter follower configs (low-z in the base, hi-z in the emitter) like >to oscillate.=20Poxy hell, you point to your own lack of understanding. That is a = totally inappropriate use of an emitter follower. No wonder you have silly problems, you don't grok electronics at all.>I always include a base resistor in things like this, >and sometimes tune it on the PC board as needed. If there's no Miller >issue (as might matter for a fast linear ramp) I just make it big, 330 >ohms or whatever, from the start and don't worry about it. > >I have dozens of products with nanosecond-scale ramp circuits in them. >They all work. I just thought I'd discuss a couple of new ideas. New >ideas seem to offend you. You'd poison a brainstorming session. > > >> >>And learn how to appropriately snip. Or is your whole object to see >>your name constantly in print ?:-) >> =09 >> ...Jim Thompson > >Design and post a fast-ramp current source that's better than any of >mine. Or even functional. > >But you can't. You don't post circuits any more. Just fuzzy-stuff >personality whining. Sad. > >I have a couple of new ones, and I'll post one soon, which it's >guaranteed you'll whine about with zero content. After lunch in the >Mission maybe.
Reply by ●August 27, 20122012-08-27
On Sun, 26 Aug 2012 21:43:00 -0700, josephkk <joseph_barrett@sbcglobal.net> wrote:>On Sun, 26 Aug 2012 12:38:59 -0700, John Larkin ><jjlarkin@highNOTlandTHIStechnologyPART.com> wrote: > >>On Sun, 26 Aug 2012 08:01:35 -0700, Jim Thompson >><To-Email-Use-The-Envelope-Icon@On-My-Web-Site.com> wrote: >> >>>On Sat, 25 Aug 2012 21:58:02 -0700, John Larkin >>><jjlarkin@highNOTlandTHIStechnologyPART.com> wrote: >>> >>>>On Sat, 25 Aug 2012 19:47:01 -0700, Jim Thompson >>>><To-Email-Use-The-Envelope-Icon@On-My-Web-Site.com> wrote: >>>> >>>>>On Sat, 25 Aug 2012 18:19:02 -0700, John Larkin >>>>><jjlarkin@highNOTlandTHIStechnologyPART.com> wrote: >>>>> >>>[snip] >>>>> >>>>>WHERE did you SHOW a WORKING circuit ?? You didn't. >>>> >>>>I've posted a bunch of current source circuits. They all work. >>> >>>In previous posts you said that the ones you attempted for your 1V/ns >>>ramp oscillated?? >> >>It depends on the PNP transistor and the value of the base resistor. A >>BCX71 oscillates at around 80 MHz, and the hotter RF parts much >>higher. It has nothing to do with the opamp gain/phase as you >>suggested; the oscillation is local to the transistor. 100 ohms in the >>base fixes it for pretty much all cases. >> >>> >>>> >>>>> >>>>>I design sub-nanosecond stuff on-chip all the time, so shove your >>>>>snarky crap up your ass. >>>>> >>>>>You're a shit "designer"... all NO-SHOW. >>>>> >>>>> ...Jim Thompson >>>> >>>>So show something of your own. >>>> >>>>You can't. >>> >>>Show us the ramp device that _doesn't_ oscillate. >> >>As noted, the proper base/gate resistor fixes it, as it does for most >>emitter-follower type circuits. Not many people appreciate how much >>emitter follower configs (low-z in the base, hi-z in the emitter) like >>to oscillate. > >Poxy hell, you point to your own lack of understanding. That is a totally >inappropriate use of an emitter follower. No wonder you have silly >problems, you don't grok electronics at all.It's not an emitter follower, but it is an "emitter-follower type circuit", namely the emitter does not see a low impedance to ground, but the base does. A base resistor is a good way to prevent VHF oscillations. This the the so-called "base stopper" or, or mosfet amps, "gate stopper" resistor in Olde English. Don't be a jerk. -- John Larkin Highland Technology Inc www.highlandtechnology.com jlarkin at highlandtechnology dot com Precision electronic instrumentation Picosecond-resolution Digital Delay and Pulse generators Custom timing and laser controllers Photonics and fiberoptic TTL data links VME analog, thermocouple, LVDT, synchro, tachometer Multichannel arbitrary waveform generators
Reply by ●August 27, 20122012-08-27
On Sun, 26 Aug 2012 21:37:00 -0700, josephkk <joseph_barrett@sbcglobal.net> wrote:>On Sat, 25 Aug 2012 17:44:16 -0700, John Larkin ><jjlarkin@highNOTlandTHIStechnologyPART.com> wrote: > >>On Sat, 25 Aug 2012 15:09:16 -0700, Jim Thompson >><To-Email-Use-The-Envelope-Icon@On-My-Web-Site.com> wrote: >> >>>On Sat, 25 Aug 2012 10:31:03 -0700, John Larkin >>><jjlarkin@highNOTlandTHIStechnologyPART.com> wrote: >>> >>>>On Sat, 25 Aug 2012 10:14:48 -0700, Jim Thompson >>>><To-Email-Use-The-Envelope-Icon@On-My-Web-Site.com> wrote: >>>> >>>>>On Sat, 25 Aug 2012 10:03:49 -0700, John Larkin >>>>><jjlarkin@highNOTlandTHIStechnologyPART.com> wrote: >>>>> >>>>>>On Sat, 25 Aug 2012 09:40:54 -0700, Jim Thompson >>>>>><To-Email-Use-The-Envelope-Icon@On-My-Web-Site.com> wrote: >>>>>> >>>>>>>On Sat, 25 Aug 2012 09:34:54 -0700, John Larkin >>>>>>><jjlarkin@highNOTlandTHIStechnologyPART.com> wrote: >>>>>>> >>>>>>>> >>>>>>>> >>>>>>>>The mounting holes on PC motherboards: are they usually connected to >>>>>>>>the PCB ground plane? >>>>>>> >>>>>>>depends. Are you wearing them like you should ?:-) >>>>>>> >>>>>>> ...Jim Thompson >>>>>> >>>>>>You never actually say anything with content any more. You don't even >>>>>>discuss circuits in any intelligent way. You've become a useless old >>>>>>hen. >>>>> >>>>>And your WORKING circuits are WHERE ?:-) >>>>> >>>>> ...Jim Thompson >>>> >>>>A few are here: >>>> >>>>http://www.highlandtechnology.com/index.shtml >>>> >>>> >>>>Any your fast current source is where? You can't do it! >>>> >>>>I rather liked the mosfet-bipolar cascode with Ib correction, but you >>>>didn't. What did you find wrong with it? I mean, aside from the fact >>>>that I invented it. Are you claiming that this *won't* work? >>>> >>>>https://dl.dropbox.com/u/53724080/Circuits/Isrc_Ib_2.JPG >>>> >>>> >>>>But I have a couple of better, cuter circuits by now. Show us your >>>>approach, and then I'll post a couple more of mine. >>>> >>>>You never say anything substantive about electronics lately. You can't >>>>invent circuits any more. Go back to sci.electronics.basics where >>>>amateurs belong. >>> >>>Show some LTspice .ASC files that can be checked. Then people will >>>believe your claims. >>> >> >>That's silly. If you can't look at a circuit and understand it, and >>decide how well it will work, and you need a simulator to do your >>thinking for you, then you are an amateur. I wouldn't Spice anything >>this simple. >> >>Good grief, you *don't* understand my circuit! > >I learned the hard way not to believe in anything without proper part >values. Nor do i spice up fragments.I rarely Spice circuits, because I design them to work. If I do Spice something, to tune it or to avoid a lot of algebra, it's only a fragment. I never even try to Spice a whole product. For really fast stuff, there aren't good enough models to make the sims worth much, especially for RF-type parts. JT gets all worked up when I post circuit topologies without values. I find that strange. It means that the only way he can evaluate a circuit is by letting Spice do the thinking for him. And he can't plug in reasonable values himself. -- John Larkin Highland Technology Inc www.highlandtechnology.com jlarkin at highlandtechnology dot com Precision electronic instrumentation Picosecond-resolution Digital Delay and Pulse generators Custom timing and laser controllers Photonics and fiberoptic TTL data links VME analog, thermocouple, LVDT, synchro, tachometer Multichannel arbitrary waveform generators
Reply by ●August 27, 20122012-08-27
On Sun, 26 Aug 2012 21:29:39 -0700, John Larkin <jjlarkin@highNOTlandTHIStechnologyPART.com> wrote:>On Sun, 26 Aug 2012 20:47:48 -0700, Jim Thompson ><To-Email-Use-The-Envelope-Icon@On-My-Web-Site.com> wrote: > >>On Sun, 26 Aug 2012 20:24:20 -0700, John Larkin >><jjlarkin@highNOTlandTHIStechnologyPART.com> wrote: >> >>>On Sun, 26 Aug 2012 22:53:35 -0400, "Tom Del Rosso" >>><td_03@verizon.net.invalid> wrote: >>> >>>> >>>>John Larkin wrote: >>>>> >>>>> You *don't* understand my circuit! >>>> >>>>I wish I did. Whether he does or not, would you mind describing it? >>> >>>This one? >>> >>>https://dl.dropbox.com/u/53724080/Circuits/Isrc_Ib_2.JPG >>> >>>U1 and the p-fet are a slow but precise closed-loop current source. >>>It's cascoded into the fast PNP transistor below, which gives us low >>>output capacitance. R3 allows the PNP emitter to move a bit and reduce >>>Early effect. R4 keeps the PNP from oscillating. >>> >>>The big DC error becomes the base current of the PNP. RF PNPs tend to >>>have have low betas, so we lose some of our precise current to the >>>base, and that changes with tempearture. So we dump the base current >>>into U2, and the resulting signal (drop across R2) increases the >>>effective reference voltage to the upper current source, increasing >>>the emitter current, almost canceling the base current error. >>> >>>R2=R1 gets us close enough. The base current cancellation is a >>>positive feedback loop, but the gain is low, basically 1/beta, so it's >>>stable. >>> >>>Jim is on record as not liking this. He won't say why. >> >>Post the circuit WITH VALUES so it can be checked. Otherwise it's a >>figment of the Napoleonic runt. >> >> ...Jim Thompson > >What you are saying is that you can't decide if it will work unless I >show all the values. Which means you can't find suitable values >yourself. Which meand you can't understand it. > >QED. > >Hint: all the resistor values can be the same.So, whatever values I pick will not be the right values? You remain a Napoleonic runt. ...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.
