On Wednesday, March 1, 2017 at 6:57:02 PM UTC-5, Jim Thompson wrote:> On Wed, 1 Mar 2017 10:20:09 -0500, Phil Hobbs > <pcdhSpamMeSenseless@electrooptical.net> wrote: > > >On 03/01/2017 09:58 AM, Jim Thompson wrote: > >> On Wed, 1 Mar 2017 06:26:23 -0800 (PST), pcdhobbs@gmail.com wrote: > >> > >>>> Take it up with Berkeley... the method has never changed... all > >>>> these years. > >>> > >>> And (AFAIK) all the copies and rewrites do it too. It's still a > >>> wart--numerical methods have come a long way since 1970, except in > >>> circuit design. > >>> > >>>> It's not like "over and over" is a big deal... noise/AC analysis > >>>> occurs about as fast as you can blink. > >>> > >>> With discrete circuits, usually so. However, lots of IC models > >>> *cough* TI op amps *cough* have ugly convergence issues even with > >>> ".savebias internal", so waiting needlessly for that 50 times is > >>> annoying. > > > >> > >> Take it up with TI and LTspice... LTspice had a lot of convergence > >> issues with analog parts that other simulators don't. > > > >Nah, ragging you is way more entertaining. > > I know >:-} > > > > >I recall your having trouble with the OPA140 in PSPICE as well. And of > >course LTspice's price is right. > > I know how to model such creatures now, but have very little time to > "play"... suddenly got busy :-) > > > > >> > >> (Also, You should read up on that important tool .STEP. You should > >> be able to do component stepping within a single run... minimizing > >> the bias recalculation.) > > > >I use .step fairly often, but in LTspice it doesn't fix the bias issues. > > Changing resistors or voltages makes the bias different on each run. > > > >Using .step to flip switches (nice infinitely differentiable ones) to > >connect INOISE to different places in the circuit shouldn't make the > >bias move, but for some reason with models like TI's OPA140 LTspice > >doesn't skip the entire bias calculation even with .savebias internal. > >(Super nice op amp, super crappy model.)> > Face it, LTspice is not that wonderful for lots of analog stuff. But > I'm back into painful land... having to use Cadence Virtuoso for a > customer... almost as bad a schematic entry as LTspice :-(Spice in general isn't that wonderful if you don't have foundry models. It's good enough to be useful, at least for discrete designs and LTC switchers, and it produces pictures for customers to show to their bosses and for posting on SED. Fortunately most of the stuff I need to simulate is discrete. Cheers Phil Hobbs
LT Spice noise analysis
Started by ●February 27, 2017
Reply by ●March 1, 20172017-03-01
Reply by ●March 1, 20172017-03-01
On Wed, 1 Mar 2017 17:39:27 -0800 (PST), pcdhobbs@gmail.com wrote:>On Wednesday, March 1, 2017 at 6:57:02 PM UTC-5, Jim Thompson wrote: >> On Wed, 1 Mar 2017 10:20:09 -0500, Phil Hobbs >> <pcdhSpamMeSenseless@electrooptical.net> wrote: >> >> >On 03/01/2017 09:58 AM, Jim Thompson wrote: >> >> On Wed, 1 Mar 2017 06:26:23 -0800 (PST), pcdhobbs@gmail.com wrote: >> >> >> >>>> Take it up with Berkeley... the method has never changed... all >> >>>> these years. >> >>> >> >>> And (AFAIK) all the copies and rewrites do it too. It's still a >> >>> wart--numerical methods have come a long way since 1970, except in >> >>> circuit design. >> >>> >> >>>> It's not like "over and over" is a big deal... noise/AC analysis >> >>>> occurs about as fast as you can blink. >> >>> >> >>> With discrete circuits, usually so. However, lots of IC models >> >>> *cough* TI op amps *cough* have ugly convergence issues even with >> >>> ".savebias internal", so waiting needlessly for that 50 times is >> >>> annoying. >> > >> >> >> >> Take it up with TI and LTspice... LTspice had a lot of convergence >> >> issues with analog parts that other simulators don't. >> > >> >Nah, ragging you is way more entertaining. >> >> I know >:-} >> >> > >> >I recall your having trouble with the OPA140 in PSPICE as well. And of >> >course LTspice's price is right. >> >> I know how to model such creatures now, but have very little time to >> "play"... suddenly got busy :-) >> >> > >> >> >> >> (Also, You should read up on that important tool .STEP. You should >> >> be able to do component stepping within a single run... minimizing >> >> the bias recalculation.) >> > >> >I use .step fairly often, but in LTspice it doesn't fix the bias issues. >> > Changing resistors or voltages makes the bias different on each run. >> > >> >Using .step to flip switches (nice infinitely differentiable ones) to >> >connect INOISE to different places in the circuit shouldn't make the >> >bias move, but for some reason with models like TI's OPA140 LTspice >> >doesn't skip the entire bias calculation even with .savebias internal. >> >(Super nice op amp, super crappy model.) > >> >> Face it, LTspice is not that wonderful for lots of analog stuff. But >> I'm back into painful land... having to use Cadence Virtuoso for a >> customer... almost as bad a schematic entry as LTspice :-( > >Spice in general isn't that wonderful if you don't have foundry models. It's good enough to be useful, at least for discrete designs and LTC switchers, and it produces pictures for customers to show to their bosses and for posting on SED. Fortunately most of the stuff I need to simulate is discrete. > >Cheers > >Phil HobbsAnd I have foundry models... this latest job is UMC, 150nm ;-) ...Jim Thompson -- | James E.Thompson | mens | | Analog Innovations | et | | Analog/Mixed-Signal ASIC's and Discrete Systems | manus | | STV, Queen Creek, AZ 85142 Skype: skypeanalog | | | Voice:(480)460-2350 Fax: Available upon request | Brass Rat | | E-mail Icon at http://www.analog-innovations.com | 1962 | Thinking outside the box... producing elegant solutions.
Reply by ●March 2, 20172017-03-02
>And I have foundry models... this latest job is UMC, 150nm ;-)You can do 150 nm litho with a crayon. Cheers Phil Hobbs
Reply by ●March 2, 20172017-03-02
On Thu, 2 Mar 2017 05:10:59 -0800 (PST), pcdhobbs@gmail.com wrote:>>And I have foundry models... this latest job is UMC, 150nm ;-) > >You can do 150 nm litho with a crayon. > >Cheers > >Phil Hobbs150 NANO-meters ?? ...Jim Thompson -- | James E.Thompson | mens | | Analog Innovations | et | | Analog/Mixed-Signal ASIC's and Discrete Systems | manus | | STV, Queen Creek, AZ 85142 Skype: skypeanalog | | | Voice:(480)460-2350 Fax: Available upon request | Brass Rat | | E-mail Icon at http://www.analog-innovations.com | 1962 | Thinking outside the box... producing elegant solutions.
Reply by ●March 2, 20172017-03-02
On 03/02/2017 09:54 AM, Jim Thompson wrote:> On Thu, 2 Mar 2017 05:10:59 -0800 (PST), pcdhobbs@gmail.com wrote: > >>> And I have foundry models... this latest job is UMC, 150nm ;-) >> >> You can do 150 nm litho with a crayon. >> >> Cheers >> >> Phil Hobbs > > 150 NANO-meters ?? > > ...Jim Thompson >Last process I worked on was 22nm, and that makes me a grandpa. ;) My nanoantennas were made on a 30-nm Leica e-beam writer, and that was getting on for a decade ago now. Cheers Phil Hobbs -- Dr Philip C D Hobbs Principal Consultant ElectroOptical Innovations LLC Optics, Electro-optics, Photonics, Analog Electronics 160 North State Road #203 Briarcliff Manor NY 10510 hobbs at electrooptical dot net http://electrooptical.net
Reply by ●March 2, 20172017-03-02
"Jim Thompson" wrote in message news:eo5fbcttk8n43vjrr2rr614ebdnmkcoiqq@4ax.com...>> > >> >I use .step fairly often, but in LTspice it doesn't fix the bias issues. >> > Changing resistors or voltages makes the bias different on each run. >> > >> >Using .step to flip switches (nice infinitely differentiable ones) to >> >connect INOISE to different places in the circuit shouldn't make the >> >bias move, but for some reason with models like TI's OPA140 LTspice >> >doesn't skip the entire bias calculation even with .savebias internal. >> >(Super nice op amp, super crappy model.) > >> >> Face it, LTspice is not that wonderful for lots of analog stuff. But >> I'm back into painful land... having to use Cadence Virtuoso for a >> customer... almost as bad a schematic entry as LTspice :-(Actually, I really like the Cadence schematic capture. LTSpice is not even in the same universe :-)> >>Spice in general isn't that wonderful if you don't have foundry models. >>It's good enough to be useful, at least for discrete designs and LTC >>switchers, and it produces pictures for customers to >show to their bosses >>and for posting on SED. Fortunately most of the stuff I need to simulate >>is discrete.>And I have foundry models... this latest job is UMC, 150nm ;-)Yeah, it is a real problem without good foundry models. I have collected quite a few sets now for all the processes I have used in my day job. Not something I can pass out with SS though. -- Kevin Aylward http://www.anasoft.co.uk - SuperSpice http://www.kevinaylward.co.uk/ee/index.html
Reply by ●March 2, 20172017-03-02
On Thu, 2 Mar 2017 05:10:59 -0800 (PST), pcdhobbs@gmail.com wrote:>>And I have foundry models... this latest job is UMC, 150nm ;-) > >You can do 150 nm litho with a crayon. > >Cheers > >Phil HobbsThat's not so. You need rubylith and x-acto knives at 150 nm. -- John Larkin Highland Technology, Inc picosecond timing precision measurement jlarkin att highlandtechnology dott com http://www.highlandtechnology.com
Reply by ●March 2, 20172017-03-02
On Thu, 2 Mar 2017 16:26:52 -0500, Phil Hobbs <pcdhSpamMeSenseless@electrooptical.net> wrote:>On 03/02/2017 09:54 AM, Jim Thompson wrote: >> On Thu, 2 Mar 2017 05:10:59 -0800 (PST), pcdhobbs@gmail.com wrote: >> >>>> And I have foundry models... this latest job is UMC, 150nm ;-) >>> >>> You can do 150 nm litho with a crayon. >>> >>> Cheers >>> >>> Phil Hobbs >> >> 150 NANO-meters ?? >> >> ...Jim Thompson >> >Last process I worked on was 22nm, and that makes me a grandpa. ;) > >My nanoantennas were made on a 30-nm Leica e-beam writer, and that was >getting on for a decade ago now. > >Cheers > >Phil HobbsSmall feature size is useless for precision Analog... VOS = 12/sqrt(W*L) (for my current process), so it goes down when area goes up. ...Jim Thompson -- | James E.Thompson | mens | | Analog Innovations | et | | Analog/Mixed-Signal ASIC's and Discrete Systems | manus | | STV, Queen Creek, AZ 85142 Skype: skypeanalog | | | Voice:(480)460-2350 Fax: Available upon request | Brass Rat | | E-mail Icon at http://www.analog-innovations.com | 1962 | Thinking outside the box... producing elegant solutions.
Reply by ●March 2, 20172017-03-02
On Thu, 2 Mar 2017 21:45:04 -0000, "Kevin Aylward" <kevinRemovAT@kevinaylward.co.uk> wrote:>"Jim Thompson" wrote in message >news:eo5fbcttk8n43vjrr2rr614ebdnmkcoiqq@4ax.com... > > >>> > >>> >I use .step fairly often, but in LTspice it doesn't fix the bias issues. >>> > Changing resistors or voltages makes the bias different on each run. >>> > >>> >Using .step to flip switches (nice infinitely differentiable ones) to >>> >connect INOISE to different places in the circuit shouldn't make the >>> >bias move, but for some reason with models like TI's OPA140 LTspice >>> >doesn't skip the entire bias calculation even with .savebias internal. >>> >(Super nice op amp, super crappy model.) >> >>> >>> Face it, LTspice is not that wonderful for lots of analog stuff. But >>> I'm back into painful land... having to use Cadence Virtuoso for a >>> customer... almost as bad a schematic entry as LTspice :-( > >Actually, I really like the Cadence schematic capture. LTSpice is not even >in the same universe :-)I'll have to check the version number tomorrow, but not nearly as bad as what I had to use 2 years ago.> >> >>>Spice in general isn't that wonderful if you don't have foundry models. >>>It's good enough to be useful, at least for discrete designs and LTC >>>switchers, and it produces pictures for customers to >show to their bosses >>>and for posting on SED. Fortunately most of the stuff I need to simulate >>>is discrete. > >>And I have foundry models... this latest job is UMC, 150nm ;-) > >Yeah, it is a real problem without good foundry models. > >I have collected quite a few sets now for all the processes I have used in >my day job. Not something I can pass out with SS though.Same here. I have literally libraries for at least 60 process variations.> > >-- Kevin Aylward >http://www.anasoft.co.uk - SuperSpice >http://www.kevinaylward.co.uk/ee/index.html...Jim Thompson -- | James E.Thompson | mens | | Analog Innovations | et | | Analog/Mixed-Signal ASIC's and Discrete Systems | manus | | STV, Queen Creek, AZ 85142 Skype: skypeanalog | | | Voice:(480)460-2350 Fax: Available upon request | Brass Rat | | E-mail Icon at http://www.analog-innovations.com | 1962 | Thinking outside the box... producing elegant solutions.
Reply by ●March 2, 20172017-03-02
On Thu, 02 Mar 2017 18:41:03 -0700, Jim Thompson <To-Email-Use-The-Envelope-Icon@On-My-Web-Site.com> wrote:>On Thu, 2 Mar 2017 16:26:52 -0500, Phil Hobbs ><pcdhSpamMeSenseless@electrooptical.net> wrote: > >>On 03/02/2017 09:54 AM, Jim Thompson wrote: >>> On Thu, 2 Mar 2017 05:10:59 -0800 (PST), pcdhobbs@gmail.com wrote: >>> >>>>> And I have foundry models... this latest job is UMC, 150nm ;-) >>>> >>>> You can do 150 nm litho with a crayon. >>>> >>>> Cheers >>>> >>>> Phil Hobbs >>> >>> 150 NANO-meters ?? >>> >>> ...Jim Thompson >>> >>Last process I worked on was 22nm, and that makes me a grandpa. ;) >> >>My nanoantennas were made on a 30-nm Leica e-beam writer, and that was >>getting on for a decade ago now. >> >>Cheers >> >>Phil Hobbs > >Small feature size is useless for precision Analog... VOS = >12/sqrt(W*L) (for my current process), so it goes down when area goes >up. > > ...Jim ThompsonDimensions are mv/um ;-) ...Jim Thompson -- | James E.Thompson | mens | | Analog Innovations | et | | Analog/Mixed-Signal ASIC's and Discrete Systems | manus | | STV, Queen Creek, AZ 85142 Skype: skypeanalog | | | Voice:(480)460-2350 Fax: Available upon request | Brass Rat | | E-mail Icon at http://www.analog-innovations.com | 1962 | Thinking outside the box... producing elegant solutions.
