Forums

don't need no opamp

Started by John Larkin January 28, 2017
If all you want to do is, say, pick resistors to get the right gain
and such, you don't need an opamp model in Spice. An 'e' thing works
just like an opamp but doesn't need power supplies. This one does what
I want to do, using only resistor values already on my board. It's a
nuisance to find a combination that works, but Spice sure beats doing
this with a calculator. I find myself Spicing really dumb passive
circuits, because it's easier than doing the math manually.


Version 4
SHEET 1 1116 680
WIRE 352 48 256 48
WIRE 416 48 352 48
WIRE 256 96 256 48
WIRE -16 112 -80 112
WIRE 112 112 64 112
WIRE 208 112 112 112
WIRE -80 128 -80 112
WIRE 416 128 416 48
WIRE 208 160 160 160
WIRE -80 240 -80 208
WIRE 256 240 256 176
WIRE -16 320 -80 320
WIRE 112 320 112 112
WIRE 112 320 64 320
WIRE 160 320 160 160
WIRE 320 320 160 320
WIRE 416 320 416 208
WIRE 416 320 320 320
WIRE -80 336 -80 320
WIRE 416 352 416 320
WIRE -80 448 -80 416
WIRE 416 480 416 432
FLAG 256 240 0
FLAG -80 240 0
FLAG -80 448 0
FLAG 416 480 0
FLAG 352 48 OUT
FLAG 320 320 FB
SYMBOL e 256 80 R0
WINDOW 0 55 42 Left 2
WINDOW 3 48 76 Left 2
SYMATTR InstName E1
SYMATTR Value 100K
SYMBOL voltage -80 112 R0
WINDOW 0 -115 38 Left 2
WINDOW 3 -111 80 Left 2
SYMATTR InstName Vref
SYMATTR Value 3.00
SYMBOL res 432 224 R180
WINDOW 0 -77 73 Left 2
WINDOW 3 -92 36 Left 2
SYMATTR InstName R1
SYMATTR Value 36.5K
SYMBOL res 80 304 R90
WINDOW 0 74 54 VBottom 2
WINDOW 3 80 49 VTop 2
SYMATTR InstName R2
SYMATTR Value 24.9K
SYMBOL res 432 448 R180
WINDOW 0 -81 81 Left 2
WINDOW 3 -102 43 Left 2
SYMATTR InstName R3
SYMATTR Value 6.49K
SYMBOL voltage -80 320 R0
WINDOW 0 -133 46 Left 2
WINDOW 123 0 0 Left 2
WINDOW 39 0 0 Left 2
WINDOW 3 -200 101 Left 2
SYMATTR InstName Vdac
SYMATTR Value PULSE(0 3 1 2)
SYMBOL res 80 96 R90
WINDOW 0 -43 55 VBottom 2
WINDOW 3 -36 53 VTop 2
SYMATTR InstName R4
SYMATTR Value 1.33K
TEXT 736 376 Left 2 !.tran 4
TEXT 512 88 Left 2 ;OPAMP REG FOR DAC-TRIMMED +20 SUPPLY
TEXT 672 256 Left 2 ;JL  Jan 27, 2017
TEXT 696 320 Left 2 ;19.36 +-0.5 V

-- 

John Larkin         Highland Technology, Inc

lunatic fringe electronics 

On Fri, 27 Jan 2017 21:18:24 -0800, John Larkin
<jjlarkin@highlandtechnology.com> wrote:

> >If all you want to do is, say, pick resistors to get the right gain >and such, you don't need an opamp model in Spice. An 'e' thing works >just like an opamp but doesn't need power supplies. This one does what >I want to do, using only resistor values already on my board. It's a >nuisance to find a combination that works, but Spice sure beats doing >this with a calculator. I find myself Spicing really dumb passive >circuits, because it's easier than doing the math manually. > > >Version 4 >SHEET 1 1116 680 >WIRE 352 48 256 48
Full schematic at... Message-ID: <8u9o8c5ul2u77f26q2vv340gpfimc09oio@4ax.com>
>TEXT 672 256 Left 2 ;JL Jan 27, 2017 >TEXT 696 320 Left 2 ;19.36 +-0.5 V
Yep. I even use Spice to solve transcendental equations. ...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 | I'm looking for work... see my website. Thinking outside the box... elegant solutions.
On Sat, 28 Jan 2017 07:46:42 -0700, Jim Thompson
<To-Email-Use-The-Envelope-Icon@On-My-Web-Site.com> wrote:

>On Fri, 27 Jan 2017 21:18:24 -0800, John Larkin ><jjlarkin@highlandtechnology.com> wrote: > >> >>If all you want to do is, say, pick resistors to get the right gain >>and such, you don't need an opamp model in Spice. An 'e' thing works >>just like an opamp but doesn't need power supplies. This one does what >>I want to do, using only resistor values already on my board. It's a >>nuisance to find a combination that works, but Spice sure beats doing >>this with a calculator. I find myself Spicing really dumb passive >>circuits, because it's easier than doing the math manually. >> >> >>Version 4 >>SHEET 1 1116 680 >>WIRE 352 48 256 48 > >Full schematic at... > >Message-ID: <8u9o8c5ul2u77f26q2vv340gpfimc09oio@4ax.com> > >>TEXT 672 256 Left 2 ;JL Jan 27, 2017 >>TEXT 696 320 Left 2 ;19.36 +-0.5 V > >Yep. I even use Spice to solve transcendental equations. > > ...Jim Thompson
What impresses me is that there's no thought of frequency compensation, but it's stable. -- John Larkin Highland Technology, Inc lunatic fringe electronics
On Sat, 28 Jan 2017 07:33:07 -0800, John Larkin
<jjlarkin@highlandtechnology.com> wrote:

>On Sat, 28 Jan 2017 07:46:42 -0700, Jim Thompson ><To-Email-Use-The-Envelope-Icon@On-My-Web-Site.com> wrote: > >>On Fri, 27 Jan 2017 21:18:24 -0800, John Larkin >><jjlarkin@highlandtechnology.com> wrote: >> >>> >>>If all you want to do is, say, pick resistors to get the right gain >>>and such, you don't need an opamp model in Spice. An 'e' thing works >>>just like an opamp but doesn't need power supplies. This one does what >>>I want to do, using only resistor values already on my board. It's a >>>nuisance to find a combination that works, but Spice sure beats doing >>>this with a calculator. I find myself Spicing really dumb passive >>>circuits, because it's easier than doing the math manually. >>> >>> >>>Version 4 >>>SHEET 1 1116 680 >>>WIRE 352 48 256 48 >> >>Full schematic at... >> >>Message-ID: <8u9o8c5ul2u77f26q2vv340gpfimc09oio@4ax.com> >> >>>TEXT 672 256 Left 2 ;JL Jan 27, 2017 >>>TEXT 696 320 Left 2 ;19.36 +-0.5 V >> >>Yep. I even use Spice to solve transcendental equations. >> >> ...Jim Thompson > >What impresses me is that there's no thought of frequency >compensation, but it's stable.
In a .OP or .DC analysis, stability isn't considered by the simulator. Being able to solve transcendental equations makes it easy for me to fit my COSH(TANH...) OpAmp transfer function to a datasheet about as fast as you can blink. ...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 | I'm looking for work... see my website. Thinking outside the box... elegant solutions.
On Sat, 28 Jan 2017 08:49:03 -0700, Jim Thompson
<To-Email-Use-The-Envelope-Icon@On-My-Web-Site.com> wrote:

>On Sat, 28 Jan 2017 07:33:07 -0800, John Larkin ><jjlarkin@highlandtechnology.com> wrote: > >>On Sat, 28 Jan 2017 07:46:42 -0700, Jim Thompson >><To-Email-Use-The-Envelope-Icon@On-My-Web-Site.com> wrote: >> >>>On Fri, 27 Jan 2017 21:18:24 -0800, John Larkin >>><jjlarkin@highlandtechnology.com> wrote: >>> >>>> >>>>If all you want to do is, say, pick resistors to get the right gain >>>>and such, you don't need an opamp model in Spice. An 'e' thing works >>>>just like an opamp but doesn't need power supplies. This one does what >>>>I want to do, using only resistor values already on my board. It's a >>>>nuisance to find a combination that works, but Spice sure beats doing >>>>this with a calculator. I find myself Spicing really dumb passive >>>>circuits, because it's easier than doing the math manually. >>>> >>>> >>>>Version 4 >>>>SHEET 1 1116 680 >>>>WIRE 352 48 256 48 >>> >>>Full schematic at... >>> >>>Message-ID: <8u9o8c5ul2u77f26q2vv340gpfimc09oio@4ax.com> >>> >>>>TEXT 672 256 Left 2 ;JL Jan 27, 2017 >>>>TEXT 696 320 Left 2 ;19.36 +-0.5 V >>> >>>Yep. I even use Spice to solve transcendental equations. >>> >>> ...Jim Thompson >> >>What impresses me is that there's no thought of frequency >>compensation, but it's stable. > >In a .OP or .DC analysis, stability isn't considered by the simulator.
My run is transient analysis, and it's stable too, with a gain of 100K and no obvious compensation.
> >Being able to solve transcendental equations makes it easy for me to >fit my COSH(TANH...) OpAmp transfer function to a datasheet about as >fast as you can blink.
You can simulate a messy equation and close a feedback loop on it to solve it in reverse. -- John Larkin Highland Technology, Inc lunatic fringe electronics
On Sat, 28 Jan 2017 09:04:54 -0800, John Larkin
<jjlarkin@highlandtechnology.com> wrote:

>On Sat, 28 Jan 2017 08:49:03 -0700, Jim Thompson ><To-Email-Use-The-Envelope-Icon@On-My-Web-Site.com> wrote: > >>On Sat, 28 Jan 2017 07:33:07 -0800, John Larkin >><jjlarkin@highlandtechnology.com> wrote: >> >>>On Sat, 28 Jan 2017 07:46:42 -0700, Jim Thompson >>><To-Email-Use-The-Envelope-Icon@On-My-Web-Site.com> wrote: >>> >>>>On Fri, 27 Jan 2017 21:18:24 -0800, John Larkin >>>><jjlarkin@highlandtechnology.com> wrote: >>>> >>>>> >>>>>If all you want to do is, say, pick resistors to get the right gain >>>>>and such, you don't need an opamp model in Spice. An 'e' thing works >>>>>just like an opamp but doesn't need power supplies. This one does what >>>>>I want to do, using only resistor values already on my board. It's a >>>>>nuisance to find a combination that works, but Spice sure beats doing >>>>>this with a calculator. I find myself Spicing really dumb passive >>>>>circuits, because it's easier than doing the math manually. >>>>> >>>>> >>>>>Version 4 >>>>>SHEET 1 1116 680 >>>>>WIRE 352 48 256 48 >>>> >>>>Full schematic at... >>>> >>>>Message-ID: <8u9o8c5ul2u77f26q2vv340gpfimc09oio@4ax.com> >>>> >>>>>TEXT 672 256 Left 2 ;JL Jan 27, 2017 >>>>>TEXT 696 320 Left 2 ;19.36 +-0.5 V >>>> >>>>Yep. I even use Spice to solve transcendental equations. >>>> >>>> ...Jim Thompson >>> >>>What impresses me is that there's no thought of frequency >>>compensation, but it's stable. >> >>In a .OP or .DC analysis, stability isn't considered by the simulator. > >My run is transient analysis, and it's stable too, with a gain of 100K >and no obvious compensation.
It's stable with gain = 1e12 too. -- John Larkin Highland Technology, Inc lunatic fringe electronics