Forums

op-amp circuit wont work

Started by panfilero July 20, 2011
On Thu, 21 Jul 2011 19:00:14 -0500, John Fields
<jfields@austininstruments.com> wrote:

>On Wed, 20 Jul 2011 21:36:14 -0700, John Larkin ><jjSNIPlarkin@highTHISlandtechnology.com> wrote: > >>On Wed, 20 Jul 2011 21:12:10 -0700, Rich Grise >><richg@example.net.invalid> wrote: >> >>>John Larkin wrote: >>>> On Wed, 20 Jul 2011 19:56:09 -0500, John S <sophi.2@invalid.org> >>>>>On 7/20/2011 7:48 PM, Jim Thompson wrote: >>>>> >>>>>> Or you can ask Larkin and he'll tell you how wonderful he is and he will >>>>>> go on and on for days... and you will know less than you do today :-) >>>>> >>>>>Of course. You just had to get that off-topic dig in didn't you? You >>>>>have become repulsive in my opinion for your inability to control >>>>>yourself. Shame on you. >>>> >>>> He's bragging that he has kill-filed me, and he's obviously obsessed >>>> by me, and pretty much dedicates all his posts to me. Figure that out. > >--- >Bragging ... me??? >Obsessed ... me??? >Dedicates... me??? > >That's not at all hard to figure out; it sounds exactly like you're a >narcissistic faggot who wants dominion over Jim by having him _want_ >to lick your "pussy", but the only way you can get that to happen is >to demean him to the point where he'll suck your dick for forgiveness, >if only figuratively.
You are getting gayer and gayer all the time. Gross.
> >In my book, that ain't ever gonna happen,
Good grief, I hope not. I don't ever want to be in the same state with the grimy old creep. Preferably not the same planet. John
On 7/21/2011 7:10 PM, John Fields wrote:
> On Thu, 21 Jul 2011 17:15:43 -0500, John S<sophi.2@invalid.org> > wrote: > >> On 7/21/2011 4:59 PM, John Fields wrote: >>> On Wed, 20 Jul 2011 21:00:18 -0700 (PDT), panfilero >>> <panfilero@gmail.com> wrote: >>> >>>> I have a follow up question about this circuit, I'm really interested >>>> in being able to measure 50uV at the input, by adding gain and seeing >>>> something at the output.... I was thinking with a gain of 21, this >>>> would get me 1.05mV at the output and I could work with that. But, >>>> when I apply zero volts at the input I get 20mV at my output. In the >>>> datasheet it says the offset voltage is below 10uV... why am I seeing >>>> this 20mV? I tried just connecting both input pins to ground and >>>> still get 20mV at the output.... also, is there any particular range >>>> of resistors that I should use in my feedback? I mean, if I want a >>>> gain of 21, I need a ratio of 20 from R2/R1.... does it matter if I >>>> use 20k/1k or 200k/10k or 2k/100? >>>> >>>> much thanks >>> >>> --- >>> Panfilero, do this, please: >>> >>> 1. Using a vanilla text editor like Notepad, set it to >>> "View All Files" and open the .asc file holding your schematic. >>> >>> 2. Select all of the text and paste it to the clipboard with "CTRL C". >>> >>> 3. Respond to this post by pasting the text (CTRL V) a couple of lines >>> below this one, and sending it. >>> >>> What that'll do is allow us all to run your simulation without each of >>> us having to manually recreate your circuit from the screen capture. >>> >>> Thanks :-) >>> >> >> >> Step 1 can also be done inside LTSpice with View/Spice Netlist > > --- > OK, but then how would you get the file to USENET? >
By following your steps 2 and 3.
On Jul 21, 4:59=A0pm, John Fields <jfie...@austininstruments.com> wrote:
> On Wed, 20 Jul 2011 21:00:18 -0700 (PDT),panfilero > > <panfil...@gmail.com> wrote: > >I have a follow up question about this circuit, I'm really interested > >in being able to measure 50uV at the input, by adding gain and seeing > >something at the output.... I was thinking with a gain of 21, this > >would get me 1.05mV at the output and I could work with that. =A0But, > >when I apply zero volts at the input I get 20mV at my output. =A0In the > >datasheet it says the offset voltage is below 10uV... why am I seeing > >this 20mV? =A0I tried just connecting both input pins to ground and > >still get 20mV at the output.... also, is there any particular range > >of resistors that I should use in my feedback? I mean, if I want a > >gain of 21, I need a ratio of 20 from R2/R1.... does it matter if I > >use 20k/1k or 200k/10k or 2k/100? > > >much thanks > > ---Panfilero, do this, please: > > 1. Using a vanilla text editor like Notepad, set it to > =A0 =A0"View All Files" and open the .asc file holding your schematic. > > 2. Select all of the text and paste it to the clipboard with "CTRL C". > > 3. Respond to this post by pasting the text (CTRL V) a couple of lines > =A0 =A0below this one, and sending it. > > What that'll do is allow us all to run your simulation without each of > us having to manually recreate your circuit from the screen capture. > > Thanks :-) > > -- > JF
thanks john Version 4 SHEET 1 880 680 WIRE 288 -192 176 -192 WIRE 0 -128 -160 -128 WIRE 176 -128 176 -192 WIRE 0 -32 0 -128 WIRE 176 -16 176 -48 WIRE -160 48 -160 -128 WIRE 288 96 288 -192 WIRE 0 144 0 48 WIRE 32 144 0 144 WIRE 160 144 32 144 WIRE 0 160 0 144 WIRE 496 160 352 160 WIRE 656 160 496 160 WIRE 672 160 656 160 WIRE 160 176 112 176 WIRE 672 192 672 160 WIRE 240 256 240 224 WIRE 240 256 208 256 WIRE 0 272 0 240 WIRE 112 272 112 176 WIRE 112 272 0 272 WIRE 208 272 208 256 WIRE 288 272 288 224 WIRE 320 272 320 224 WIRE 320 272 288 272 WIRE 0 304 0 272 WIRE 672 304 672 272 WIRE 288 320 288 272 WIRE 288 320 96 320 WIRE 256 336 256 224 WIRE 368 336 256 336 WIRE 496 336 496 160 WIRE 496 336 448 336 WIRE 96 384 96 320 WIRE 256 416 256 336 WIRE 96 512 96 464 WIRE 256 608 256 496 FLAG 176 -16 0 FLAG 672 304 0 FLAG 96 512 0 FLAG -160 48 0 FLAG 0 304 0 FLAG 656 160 Vout FLAG 208 272 0 FLAG 256 608 0 FLAG 32 144 Vin SYMBOL voltage 176 -144 R0 WINDOW 123 0 0 Left 0 SYMATTR InstName V1 SYMATTR Value 5 SYMATTR SpiceLine Rser=3D.000001 SYMBOL Opamps\\LTC2053 272 160 R0 SYMATTR InstName U1 SYMBOL res 240 400 R0 SYMATTR InstName R1 SYMATTR Value 1K SYMATTR SpiceLine tol=3D1 pwr=3D0.1 SYMBOL res 352 352 R270 WINDOW 0 32 56 VTop 0 WINDOW 3 0 56 VBottom 0 SYMATTR InstName R2 SYMATTR Value 200k SYMATTR SpiceLine tol=3D1 pwr=3D0.1 SYMBOL res -16 144 R0 SYMATTR InstName R3 SYMATTR Value 1 SYMBOL res 656 176 R0 SYMATTR InstName R4 SYMATTR Value 500000000 SYMATTR SpiceLine tol=3D1 pwr=3D0.1 SYMBOL voltage 96 368 R0 WINDOW 123 0 0 Left 0 SYMATTR InstName V2 SYMATTR Value -5 SYMATTR SpiceLine Rser=3D.0001 SYMBOL current 0 -32 R0 WINDOW 123 0 0 Left 0 WINDOW 39 0 0 Left 0 SYMATTR InstName I1 SYMATTR Value -0.017 TEXT -120 592 Left 0 !.tran 0 0.25 0 .01 uic
On Thu, 21 Jul 2011 20:37:39 -0500, John S <sophi.2@invalid.org>
wrote:

>On 7/21/2011 7:10 PM, John Fields wrote: >> On Thu, 21 Jul 2011 17:15:43 -0500, John S<sophi.2@invalid.org> >> wrote:
>>> Step 1 can also be done inside LTSpice with View/Spice Netlist >> >> --- >> OK, but then how would you get the file to USENET? >> > >By following your steps 2 and 3.
--- Dunno how I missed that one! :-( Thanks! :-) -- JF
On Thursday, July 21, 2011 5:10:32 PM UTC-4, George Herold wrote:

[about converting current to voltage] 

>.... How about using a 'regular' opamp as a > transimpedance amp to measure the current. Currents from 50 uA to 100 > uA are no big deal at all. (I've measured pA with a TIA and a Gig-ohm > resistor) A 100k ohm resistor in the feedback would give 10 Volts on > the output for 100uA of current.
I second this; the op amp (-) node takes the input current and has a feedback resistor from the output, then a second (match to the feedback) resistor goes from (+) to ground.
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Jim Thompson wrote:

> You sure must live in a cave... I am the resident "kill any liberal on =
sight"
> proponent. >=20 > You could be next :-)
Traveling? I hear Oslo is beautiful this time of year. Everything's just so RIGHT. mike --------------enigA18F48B1FB7542CAB01E53AF Content-Type: application/pgp-signature; name="signature.asc" Content-Description: OpenPGP digital signature Content-Disposition: attachment; filename="signature.asc" -----BEGIN PGP SIGNATURE----- Version: GnuPG v2.0.17 (GNU/Linux) iQEcBAEBAgAGBQJOKv10AAoJECGtZwCbtgwXvlIH/iuIyn1Tzkj0ZEVdTLLprK71 MF5lqva+Fkk6vO9NP1cWyO+HzW5GMRcC2ai9ZWaNa6UFvljiSHn4s6N33+Vw6UBV h/SZUF2m6B9gFgtEaSSBmYKb/ufYBuDDcNwdDRoCvo2gR/z8uhlY0uO2NUzrZ3Ly xchdz7goJPjiFBK6shbR9suRWTmMhgPnYCqTvdQFh2Cpi7yY7h6Z4rIzSLTSSb4y /oTLa393zvGUyEKet7swui1xUPgyyKkwd/5SVEWPtxNC90V5Ub48u1bCtCdQDqq3 A2gPM4etjyX5brf2CcRe78PteFtiQJild+BHfd8uE6rf1HqFiYjly2T4yIzy45E= =L1/H -----END PGP SIGNATURE----- --------------enigA18F48B1FB7542CAB01E53AF--
On 7/21/2011 5:15 PM, John S wrote:
> On 7/21/2011 4:59 PM, John Fields wrote: >> On Wed, 20 Jul 2011 21:00:18 -0700 (PDT), panfilero >> <panfilero@gmail.com> wrote: >> >>> I have a follow up question about this circuit, I'm really interested >>> in being able to measure 50uV at the input, by adding gain and seeing >>> something at the output.... I was thinking with a gain of 21, this >>> would get me 1.05mV at the output and I could work with that. But, >>> when I apply zero volts at the input I get 20mV at my output. In the >>> datasheet it says the offset voltage is below 10uV... why am I seeing >>> this 20mV? I tried just connecting both input pins to ground and >>> still get 20mV at the output.... also, is there any particular range >>> of resistors that I should use in my feedback? I mean, if I want a >>> gain of 21, I need a ratio of 20 from R2/R1.... does it matter if I >>> use 20k/1k or 200k/10k or 2k/100? >>> >>> much thanks >> >> --- >> Panfilero, do this, please: >> >> 1. Using a vanilla text editor like Notepad, set it to >> "View All Files" and open the .asc file holding your schematic. >> >> 2. Select all of the text and paste it to the clipboard with "CTRL C". >> >> 3. Respond to this post by pasting the text (CTRL V) a couple of lines >> below this one, and sending it. >> >> What that'll do is allow us all to run your simulation without each of >> us having to manually recreate your circuit from the screen capture. >> >> Thanks :-) >> > > > Step 1 can also be done inside LTSpice with View/Spice Netlist
I owe you an apology. It *appeared* that it could be done, but I was wrong. Too much is missing from that netlist to give a schematic. I did not try it before submitting the suggestion. Dang me. Sorry. Your steps are the best route. John S
On Sat, 30 Jul 2011 14:36:58 -0500, John S <sophi.2@invalid.org>
wrote:

>On 7/21/2011 5:15 PM, John S wrote: >> On 7/21/2011 4:59 PM, John Fields wrote: >>> On Wed, 20 Jul 2011 21:00:18 -0700 (PDT), panfilero >>> <panfilero@gmail.com> wrote: >>> >>>> I have a follow up question about this circuit, I'm really interested >>>> in being able to measure 50uV at the input, by adding gain and seeing >>>> something at the output.... I was thinking with a gain of 21, this >>>> would get me 1.05mV at the output and I could work with that. But, >>>> when I apply zero volts at the input I get 20mV at my output. In the >>>> datasheet it says the offset voltage is below 10uV... why am I seeing >>>> this 20mV? I tried just connecting both input pins to ground and >>>> still get 20mV at the output.... also, is there any particular range >>>> of resistors that I should use in my feedback? I mean, if I want a >>>> gain of 21, I need a ratio of 20 from R2/R1.... does it matter if I >>>> use 20k/1k or 200k/10k or 2k/100? >>>> >>>> much thanks >>> >>> --- >>> Panfilero, do this, please: >>> >>> 1. Using a vanilla text editor like Notepad, set it to >>> "View All Files" and open the .asc file holding your schematic. >>> >>> 2. Select all of the text and paste it to the clipboard with "CTRL C". >>> >>> 3. Respond to this post by pasting the text (CTRL V) a couple of lines >>> below this one, and sending it. >>> >>> What that'll do is allow us all to run your simulation without each of >>> us having to manually recreate your circuit from the screen capture. >>> >>> Thanks :-) >>> >> >> >> Step 1 can also be done inside LTSpice with View/Spice Netlist > >I owe you an apology. It *appeared* that it could be done, but I was >wrong. Too much is missing from that netlist to give a schematic. I did >not try it before submitting the suggestion. Dang me. Sorry. > >Your steps are the best route.
--- Thanks for that, and thanks for the heads-up as well; I didn't try it either. As for the apology: You, Sir, are a true gentleman. :-) -- JF
On 7/30/2011 3:20 PM, John Fields wrote:
> On Sat, 30 Jul 2011 14:36:58 -0500, John S<sophi.2@invalid.org> > wrote: > >> On 7/21/2011 5:15 PM, John S wrote: >>> On 7/21/2011 4:59 PM, John Fields wrote: >>>> On Wed, 20 Jul 2011 21:00:18 -0700 (PDT), panfilero >>>> <panfilero@gmail.com> wrote: >>>> >>>>> I have a follow up question about this circuit, I'm really interested >>>>> in being able to measure 50uV at the input, by adding gain and seeing >>>>> something at the output.... I was thinking with a gain of 21, this >>>>> would get me 1.05mV at the output and I could work with that. But, >>>>> when I apply zero volts at the input I get 20mV at my output. In the >>>>> datasheet it says the offset voltage is below 10uV... why am I seeing >>>>> this 20mV? I tried just connecting both input pins to ground and >>>>> still get 20mV at the output.... also, is there any particular range >>>>> of resistors that I should use in my feedback? I mean, if I want a >>>>> gain of 21, I need a ratio of 20 from R2/R1.... does it matter if I >>>>> use 20k/1k or 200k/10k or 2k/100? >>>>> >>>>> much thanks >>>> >>>> --- >>>> Panfilero, do this, please: >>>> >>>> 1. Using a vanilla text editor like Notepad, set it to >>>> "View All Files" and open the .asc file holding your schematic. >>>> >>>> 2. Select all of the text and paste it to the clipboard with "CTRL C". >>>> >>>> 3. Respond to this post by pasting the text (CTRL V) a couple of lines >>>> below this one, and sending it. >>>> >>>> What that'll do is allow us all to run your simulation without each of >>>> us having to manually recreate your circuit from the screen capture. >>>> >>>> Thanks :-) >>>> >>> >>> >>> Step 1 can also be done inside LTSpice with View/Spice Netlist >> >> I owe you an apology. It *appeared* that it could be done, but I was >> wrong. Too much is missing from that netlist to give a schematic. I did >> not try it before submitting the suggestion. Dang me. Sorry. >> >> Your steps are the best route. > > --- > Thanks for that, and thanks for the heads-up as well; I didn't try it > either. > > As for the apology: You, Sir, are a true gentleman. :-) >
And, you are a true gentleman for writing that. I believe in admitting my mistakes, whether minor or major. Cheers, John S