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Original question:

LMP7721 Tina TI Noise Simulation

WEBENCH® Tools/OPA377: opa377

Sean Lastuka41
Prodigy 40 points
Part Number: OPA377
Other Parts Discussed in Thread: TINA-TI

Tool/software: WEBENCH® Design Tools

I am attempting to make a TINA-TI noise simulation w the opa377.  After finishing the schematic, I run a ac analysis and the results are as expected.  A noise analysis plot also looks reasonable.  However, the exported noise analysis text output doesn't make sense.  I think it should have a column for frequency and second column for the noise value in units of V/rt(Hz).  Below are a few lines...  In the plot, these values are about 800E-9 down to 300E-9.  Anyone know a solution?

*Frequency VM1-abs VM1-phase (deg)
0.1 2.18707013272029E-7 4.55785877917367E-5
0.117489755493953 2.0935011595101E-7 3.71340625965945E-5
0.138038426460288 2.0137867575158E-7 3.04028477318039E-5
0.162181009735893 1.94745920886315E-7 2.50248370210607E-5
0.190546071796325 1.89414678866716E-7 2.07166450238137E-5
0.223872113856834 1.85357305866075E-7 1.72551806465524E-5
0.263026799189538 1.82555748342336E-7 1.44647472336397E-5

  • 0
    TI__Guru 51491 points

    Hi Sean,

    I am unable to comment on your plot, but I can try to explain the numbers below. If you still have the question, please post the schematic.

    0.117489755493953 2.0935011595101E-7 3.71340625965945E-5

    0.117489755493953 means the frequecy is 0.118Hz or 118mHz, I think that you start at 100mHz

    2.0935011595101E-7 means 2.094e-7 V/sqrt(Hz), which converts to 209.4 nV/sqrt(Hz)

    3.71340625965945E-5 is phase angle in degree

    From the OPA377 datasheet, attached is the input voltage noise spectral density. The 1Hz input voltage noise is approx. 50+ nV/sqrt(Hz). If frequency is lowered by a decade at 0.1Hz, 218.7nV/sqrt(Hz) is not unreasonable. 

    Best,

    Raymond

  • 0 in reply to Raymond Zhang1
    Prodigy 40 points

    Thank you for the response Raymond.  I agree the text output appears to be the voltage noise from the actual op-amp.

    However, we have surrounding passives to form filters.  When I run an 'input noise' analysis I see a cup-shaped curve.  However, when I save that plotted data as a text file, I am pretty sure the values don't match up.  The spice model, plot screenshot and text output of the plot are attached. 

    I am making a mistake in the use of this tool?  s2.TSC

    tcurve1.txt 
    *Frequency 	VM1-abs	VM1-phase (deg)
0.1	1.78439165304378E-7	0.000162717222903259
0.117489755493953	1.65663133444845E-7	0.000128578815585354
0.138038426460288	1.53978571547891E-7	0.000101719478269218
0.162181009735893	1.43313250226025E-7	8.05806156322104E-5
0.190546071796325	1.33602394457766E-7	6.39379969445623E-5
0.223872113856834	1.24788407566195E-7	5.08299620767353E-5
0.263026799189538	1.16820646721674E-7	4.05010419093197E-5
0.309029543251359	1.09655237389332E-7	3.23576828340369E-5
0.363078054770101	1.03254908669922E-7	2.59334762455203E-5
0.426579518801593	9.75888252030363E-8	2.08618525459437E-5
0.501187233627272	9.2632385400932E-8	1.6854638003094E-5
0.588843655355589	8.83669524640111E-8	1.36852175150617E-5
0.691830970918937	8.47794871760604E-8	1.11753170387278E-5
0.812830516164099	8.18620637164512E-8	9.18463180458589E-6
0.954992586021436	7.96112745479672E-8	7.6026926669925E-6
1.12201845430196	7.80275673464518E-8	6.34249258343759E-6
1.31825673855641	7.71145995228547E-8	5.33549593649951E-6
1.54881661891248	7.68787311992782E-8	4.5277315957788E-6
1.81970085860998	7.73287894438603E-8	3.87673178087182E-6
2.13796208950223	7.84762133996669E-8	3.34912762226023E-6
2.51188643150958	8.03356321110332E-8	2.91875242481051E-6
2.95120922666639	8.29258491421946E-8	2.56513722978012E-6
3.46736850452532	8.6271132720535E-8	2.27231122023528E-6
4.07380277804113	9.04026542982792E-8	2.02784189795374E-6
4.78630092322638	9.53598842629118E-8	1.82206681425807E-6
5.62341325190349	1.01191726480081E-7	1.64748048662902E-6
6.60693448007596	1.07957127815498E-7	1.49824803610224E-6
7.76247116628692	1.15724805615982E-7	1.36982231899188E-6
9.12010839355911	1.2457156765938E-7	1.25864503357815E-6
10.7151930523761	1.34578431757835E-7	1.16191523239592E-6
12.5892541179417	1.45823371651727E-7	1.07741126753076E-6
14.7910838816821	1.5836903247251E-7	1.00335457906504E-6
17.3780082874938	1.72243245298627E-7	9.38305907713155E-7
20.4173794466953	1.87409832014712E-7	8.81086431740053E-7
23.9883291901949	2.03727477926921E-7	8.30717963548227E-7
28.1838293126446	2.20896166173493E-7	7.86377685681185E-7
33.1131121482591	2.38394956183197E-7	7.47363975731207E-7
38.9045144994281	2.55422759365962E-7	7.1307069687659E-7
45.7088189614875	2.70864793814783E-7	6.8296795552799E-7
53.7031796370253	2.8331766828681E-7	6.56587791674859E-7
63.0957344480194	2.91207018447375E-7	6.3351361049255E-7
74.1310241300918	2.93013367965362E-7	6.13372420028568E-7
87.0963589956082	2.87582027075546E-7	5.95829137023426E-7
102.329299228075	2.74444399539575E-7	5.80582381400887E-7
120.226443461741	2.54045341576271E-7	5.67361312835162E-7
141.253754462276	2.27775701598741E-7	5.55923177334516E-7
165.958690743756	1.97760567451282E-7	5.46051331176052E-7
194.984459975805	1.66444699669316E-7	5.37553594887174E-7
229.086765276777	1.36109837822535E-7	5.30260861949771E-7
269.153480392692	1.08492544243467E-7	5.2402594679573E-7
316.227766016838	8.46133089989543E-8	5.18722706876077E-7
371.535229097173	6.4818416013601E-8	5.14245517657411E-7
436.515832240166	4.89531505316337E-8	5.10509221737199E-7
512.861383991365	3.65683245538242E-8	5.07449718804137E-7
602.559586074359	2.70939368567585E-8	5.05025416970716E-7
707.945784384139	1.99556418309025E-8	5.03219832796447E-7
831.763771102673	1.46379432879458E-8	5.02045710659348E-7
977.237220955811	1.07092280996804E-8	5.01551132822273E-7
1148.15362149688	7.82408338572634E-9	5.01828204607246E-7
1348.96288259166	5.7144003207465E-9	5.0302500846373E-7
1584.89319246112	4.1764158033463E-9	5.05361590803163E-7
1862.08713666287	3.05752866383287E-9	5.09150709948224E-7
2187.76162394955	2.244621366688E-9	5.1482382532176E-7
2570.39578276886	1.65444188539974E-9	5.22962202783702E-7
3019.95172040202	1.22602036326831E-9	5.34331911014337E-7
3548.13389233576	9.14855344667419E-10	5.49919879871838E-7
4168.69383470335	6.88540118546124E-10	5.70966420818074E-7
4897.78819368447	5.23515858783438E-10	5.98988575471151E-7
5754.39937337157	4.02684130065368E-10	6.35789750512996E-7
6760.82975391982	3.13662453383635E-10	6.83455403230943E-7
7943.28234724283	2.47513102375885E-10	7.4434144122542E-7
9332.54300796993	1.9781488075559E-10	8.21068393102918E-7
10964.7819614319	1.59981037264724E-10	9.16536253875989E-7
12882.4955169314	1.30754307633579E-10	1.03397060071238E-6
15135.6124843621	1.07831836646787E-10	1.17700274058747E-6
17782.7941003893	8.95878845091543E-11	1.34978001939636E-6
20892.9613085404	7.48714719049473E-11	1.55710000030317E-6
24547.0891568503	6.28613872772198E-11	1.80456375505123E-6
28840.3150312661	5.29643035779339E-11	2.09874689381782E-6
33884.4156139203	4.47444158473082E-11	2.44739023613592E-6
39810.7170553498	3.78754693002058E-11	2.8596142688114E-6
46773.5141287199	3.21082898248144E-11	3.34616259377204E-6
54954.0873857625	2.72488340677474E-11	3.9196794588057E-6
64565.4229034657	2.31432793541921E-11	4.5950248262471E-6
75857.7575029186	1.96677886348104E-11	5.38962594584923E-6
89125.0938133745	1.67213745737092E-11	6.32385376273527E-6
104712.85480509	1.42208260570185E-11	7.42138826888131E-6
123026.877081238	1.20970198399516E-11	8.70948278870778E-6
144543.977074593	1.02921756203562E-11	1.02189180721241E-5
169824.365246175	8.75776554363818E-12	1.19831794564366E-5
199526.231496888	7.45288757350834E-12	1.40358487661178E-5
234422.881531993	6.34297551690606E-12	1.64041234831615E-5
275422.870333817	5.398759393187E-12	1.90944578713254E-5
323593.656929629	4.59541645876334E-12	2.20638001664518E-5
380189.396320562	3.9118707776283E-12	2.51698871090377E-5
446683.592150963	3.33021108378424E-12	2.81078317431315E-5
524807.460249773	2.83520483711357E-12	3.03863484538058E-5
616595.001861483	2.41389193068748E-12	3.14528333554508E-5
724435.96007499	2.05524495145532E-12	3.0994996309603E-5
851138.038202377	1.74988456056804E-12	2.91688685914033E-5
999999.999999999	1.48983920819262E-12	2.64786940073201E-5

  • 0 in reply to Sean Lastuka41
    TI__Guru 51491 points

    Hi Sean,

    Can you send me the Tina simulation? The txt file does not match the plot.

    I used the export txt features a lot with more complicated plots (just two days ago), and I never see the issue. There were instance that I exported the file to a wrong folder with duplicated names. I was wondering if that is a possibility here. 

    Best,

    Raymond

  • 0 in reply to Raymond Zhang1
    Prodigy 40 points

    HI Raymond, 

    I don't know how to send a simulation.  

    Perhaps, would you be able to open S2.TSC (attached) 2664.s2.TSCand run noise analysis? 

    For 'noise analysis' options, I only plotted 'input noise' and I ran it from 0.1Hz to 1MHz.  

  • 0 in reply to Sean Lastuka41
    TI__Guru 51491 points

    Hi Sean,

    Here is what happened. The file is sent out as Frequency, VM1 output and VM1 phase angle. At 100mHz, VM1=1.78e-7V and its gain = -24.04 dB. The input noise figure is presented at 2.84 uV/sqrt(Hz). 

    You have to convert -24.04dB to Gain figure, which is 10^(-24.04/20) = 0.062805. Then you VM1/Gain = 1.78e-7V/0.062805 = 2.83e-6 V or 2.83 uV

    Let us pick another point 0.95499 Hz, which is last point in the captured image. The input noise is measured at 132.69nV/sqrt(Hz). Gain at 0.95499 Hz is -4.44dB or 0.59979. The output VM1 noise/sqrt(Hz) should be Gain*input noise = 0.59979*132.69nV = 7.9586e-8 V/sqrt(Hz) or 7.96e-8 shown in the table. 

    I would suggest to cut and pass the Input noise plot from Tina. Otherwise, you have to output Gain(dB)  and VM1 Noise Plot (V/sqrt(Hz), and convert the plot as shown in the file below.  

    Frankly, I do not go through the process normally. If you have other questions, please let me know. 

    /cfs-file/__key/communityserver-discussions-components-files/234/Input-Noise-OPA377-07062020.xlsx

    Best,

    Raymond

  • 0 in reply to Raymond Zhang1
    Prodigy 40 points

    Thank you Raymond!  Totally makes sense.  :) 

    Sean