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DC Operating Point At Cadence After finishing your problem, save and check it or simply press x. If not, I guess I could export the data in tabular form. In the input.scs file, I do see the include directive for "save.scs" so I don't really know what could be wrong. I'm not sure why it should take 2.5s in interactive mode (I would suggest you contact customer support so we can take a look - this seems really excessive). Talking about Matlab, the association is with co-simulation (rhyme unintended), and then, with system level simulations. However, do note that the dc solution for transient will start from the values at the end of the previous simulation - and so that would be the value of x=1.8 (because of the dc sweep). gm=cds_srr('./idcurvesw.raw','sweepvgs_dc-sweep','m1:gm');contour(getfield(gm,'vgs:dc'),gm.dc,gm.S); (could use mesh instead of contour to see a graph). VN) resistor r=1KV3 (net08 net07) vsource dc=600.0m type=dcV2 (net016 0) vsource dc=x type=dcV0 (vdd! I don't think in general that restart is going to make much difference in this case. If you need to use both Cadence tools and Synopsys tools, use them in different terminals (tabs), e.g. The question is, is it possible to:1. run 1st dc sweep2. I just run DC and transient analyses to find the operating point. It also provides concept of design variable in cadence virtuoso. p.s. The DC value will be used for the operatioing point analysis and DC sweep. Cadence tutorial : DC analysis and DC sweep in cadence 47,768 views Aug 18, 2014 This is a very basic tutorial for beginners. However, I think I was not clear in my first post. V Points: 2 Helpful Answer Positive Rating Jul 10, 2013 Jan 12, 2006 #5 rfsystem Advanced Member level 3 Joined Feb 25, 2002 Messages 910 Helped 149 Reputation 294 Reaction score 37 Trophy points 1,308 Location I have attached a zip with 3 screenshots showing the testbench, the simulation windows, and the (incredibly complex) save.scs file :), saveOptions options save=al currents=all subcktprobelvl=2. The absolute tolerances are for when the signal levels are close to zero - because otherwise you'd have an ever increasing accuracy for tiny (insignificant) signals. You can do this by creating an ASCII file somewhere, with: save M1 or: save M1:oppoint or save M1:gm M1:gds M1:vdsat in the file, and then adding this as a model library in ADE (effectively as an include file). Having done this, you should be able to access the resulting operating point data from the DC sweep from the results browser, and then you'll get a plot of it versus your sweep. They are actually very closed to each other (2pA difference) but should they be exact the same? I have just checked it the way you did and the result is same now. I tried to check the voltage at two inputs to see if the operating point is beginning or final point and the result confirms that it is beginning point (if nothing goes wrong). save calculated dc operating point3. which is the operating point at theend of the simulation, not the beginning. Perhaps all you need to do is add ?restart "no" to the analysis function? I tried to setreltol = 1e-8 but the resulting current in tran analysis is still not the same: iM0=800.001uA and iM1=799.999uA. For example, if the inner sweep is VGS and outer sweep VDS, a slice of the inner sweep would be: or if you want to do it for the outer sweep (the value function works by default on the inner sweep), you could do: value(getData("M1:gm" ?result 'dc) 'VDS 0.6) ; where 'VGS is the name of the swept variable, Otherwise you can save the data to a table - which version of Virtuoso are you using? I suppose another alternative is to use python to generate a really big netlist with all of my operating points which may be a few thousand, and just get them all at once in parallel. . What this is doing is telling it to additionally save the operating point data (or specifically gm) for a single transistor or set of transistors. Transient analysis will perform DC analysis first, so should they be equal? You need to specify it before you run the sim. Not for every dc sweep. The DC analysis may fail to converge because of incorrect initial voltage estimates, model discontinuities, unstable/bistable operation, or unrealistic circuit impedances. In this case the difference is insignificant. Note I used the "unaliased" result name to ensure it worked in all versions (normally results() and ViVA results browser show the aliased result name to make it more portable and shorter). I also wrote this short OCEAN script to get the results: openResults("forum_oppoint.raw");println(results());println(results(?noAlias t))selectResult("dcOpInfo")printf("M0:id = %g M1:id = %g\n" getData("M0:id") getData("M1:id"))selectResult("tran_info-tran_info")printf("M0:id = %g M1:id = %g\n" value(getData("M0:id") 0) value(getData("M1:id") 0)). I don't think thattheVisualization Tool is equipped for plotting surfaces but actually what I need is plotting contours (slices of my surface). However, do note that the dc solution for transient will start from the values at the end of the previous simulation - and so that would be the value of x=1.8 (because of the dc sweep). I wasn't sure if what Lawrence has suggested was quite what you were after, but maybe all you need is to add ?write "tran.fc" to the dc analysis? The save statement tells it to save this info for all analyses run. If it's set to "batch" then do: envSetVal ("spectre.envOpts" "controlMode" 'string "interactive") and restart ADE L and try the parametric analysis tool again. Similarly if you did a transient you could plot the gm versus time using this approach. or. Especially, when the simulator meets convergence problems and switches homotopy methods. There are chapters on the different analysis types for DC Bias point, DC sweep, AC frequency sweep, Parametric analysis, Temperature analysis, Performance Analysis, Noise analysis, Sensitivity and Monte Carlo simulation. The first field "dcs" is the name of the dc sweep (can be any alphanumeric name). If the circuit has more than one stable operating point, then that could influence the result. Figure 8: DC and AC Simulation Setup . You can also do system simulation using AMS Designer - provided that you have Verilog/Verilog AMS/VHDL/VHDL AMS/SystemVerilog models to do so (there are some libraries included in the software). I can't print the operating points in ADE because I don't have the setup, but if I look in the results browser, then I see "tranOp" (which is the aliased name for the finalTimeOP results) and "tranOpTimed" which is the aliased name for the "infotimes" output. I would really like - if possible - to stay in Cadence for all IC related work, also for the "big picture" stages of the design. Then reference this file using Setup->Model Libraries in ADE. To quote "Virtuoso Spectre Circuit Simulator Reference October 2014" manual: "restart=yes Restart from scratch if any condition has changed. 1. I got the RF library installed by the (allmighty) CAD support here, and the matlab importfunctions work perfectly for my purpose. I can't remember which IC version you're using, but I ran the simulation using MMSIM13.1 Update - which is 13.1.1.049. Save operating point information over a DC sweep You may notice that DC operating point information (gm, gds, etc.) Transient and DC operating point are different, DC : M0:id = 0.00079999999976654 M1:id = 0.00079999999976654, TRAN 0: M0:id = 0.00079999999976654 M1:id = 0.00079999999976654, FINAL : M0:id = 0.00080000135675758 M1:id = 0.00079999851611377, printf("DC : M0:id = %.14g M1:id = %.14g\n" getData("M0:id") getData("M1:id")), printf("TRAN 0: M0:id = %.14g M1:id = %.14g\n" value(getData("M0:id") 0) value(getData("M1:id") 0)), printf("FINAL : M0:id = %.14g M1:id = %.14g\n" getData("M0:id") getData("M1:id")). Normally this doesn't happen for DC sweeps, just DC operating points - in order to prevent a huge amount of data being produced that most of the time you don't need. As you can see the transient operating point for id at the time zero: DC : M0:id =800.000003e-6 M1:id =800.000003e-6, TRAN 0: M0:id = 800.000003e-6M1:id =800.000003e-6. The operating conditions would always be changing here, and so it's always going to start from the previous initial guess. I checked the node voltages and currents and they all seem to be the same (comparing the spectre.ic and spectre.dc files). As you can see, the dcOpInfo and tran_info-tran_info results match: By the way, I wouldn't set the reltol that tight - that's excessive. for example : . So this means you then don't have to load it and then export it to CSV to read back into Matlab; it can directly read the PSF results into Matlab. Result=>Annotate=>DC operating points. (Help->About in the CIW). I got this by running each analysis separately and then from ADE print operating points. The value of the forward transconductance varies with the Q point on the curve. - how would you rate Cadence' suite "user-friendliness" to perform (and quickly setup) system-level simulations? use Cadence in one terminal, and use HSPICE in another, after sourcing proper profiles. . Simple way to do it is using Parametric Analysis. // which suggests we can't get operating point versus a sweep parameter, but that // is not quite right dc dc param=v_vgs start=0 stop=1.5 lin=200 oppoint=rawfile maxiters=150 \ maxsteps=10000 annotate=status // this is the line which saves some of the small signal operating point parameters 5. Note you can also just use delete('analysis 'tran) to remove the tran analysis after running it the first time, rather than having to set the analysisOrder. What I see the difference is currents through M0 and M1 in two cases. Honestly I would like to see it works at least one time myself. thank you so much for helping. Some will be scalar, some will be vector. I'd say your best bet is to contact Cadence (either via customer support, or via your account manager) so we can discuss in more detail your requirements. It's not possible to get an exact solution to such equations, so numerical methods are employed (e.g. This means that my gm will become a bidimensional functionA surface in a three dimensional space. Thank you both for your suggestions. However, that is not the case in my simulation. That's what I would have expected - so there's going to be no benefit of using a nodeset between points in the sweep (not that you can do it anyway). A careful inspection of 'spectre -h dc' would seem to imply that indeed you can't save off operating points as part of a dc parameter sweep. It does not look like the next dc step uses an operating point calculated in a previous dc step, what most probably would be ideal. The question is, is it possible to: 1. run 1st dc sweep 2. save calculated dc operating point 3. start 2nd sweep 4. load dc operating point from the 1st sweep 5. run 2nd sweep 6. save dc operating point of 2nd sweep I can already plot my values in excel and can certainly do a better job in Matlab. Also, I tried to choose stop time equal to an even number of cycle so that the final point and beginning point are the same with both two input starting at the same value). There is an enhancement request (for some time) requesting an easy way to set up these save statements and access the results from the UI, but it's not been implemented yet. You could add this in your save.scs : I made the filename have %T so that it has a timestamp in there for each point in the parametric sweep - but this is a bit clunky. So a difference of only 2pA is remarkably small (it's close to the abstol), especially in a current of 800uA. If it was so, there would be no difference between cases 1 and 2 except the first dc step operating point calculations. load dc operating point from the 1st sweep5. However, in transient analysis, I tried to set infoitimes box with 0 but the result in result browser doesn't have any infor about oppoint at this time. The AC value may combine with DC value to set the operating point for the . After that, each point in the DC sweep is probably close to the previous one and hence it converges quickly. There's probably some longer term settling effect - I found this reduced if I ran a much longer simulation with a lower frequency sine wave too. 0) vsource dc=1.8 type=dcV6 (Vin2 net016) vsource mag=1 type=sine ampl=1m sinephase=180 freq=1MV5 (Vin net016) vsource mag=1 type=sine ampl=1m sinephase=0 freq=1MI11 (VS 0) isource dc=1.6m type=dcM3 (net015 net08 net07 net07) nch l=180n w=2u m=50 ad=5.4e-13 as=5.568e-13 \ pd=2.54u ps=2.6368u nrd=0.135 nrs=0.135M1 (VP Vin2 VS VS) nch l=180n w=2u m=50 ad=5.4e-13 as=5.568e-13 pd=2.54u \ ps=2.6368u nrd=0.135 nrs=0.135M0 (VN Vin VS VS) nch l=180n w=2u m=50 ad=5.4e-13 as=5.568e-13 pd=2.54u \ ps=2.6368u nrd=0.135 nrs=0.135simulatorOptions options reltol=1e-3 vabstol=1e-6 iabstol=1e-12 temp=27 \ tnom=27 scalem=1.0 scale=1.0 gmin=1e-12 rforce=1 maxnotes=5 maxwarns=5 \ digits=5 cols=80 pivrel=1e-3 sensfile="../psf/sens.output" \ checklimitdest=psf dcOp dc write="spectre.dc" maxiters=150 maxsteps=10000 annotate=statusdcOpInfo info what=oppoint where=rawfiledc dc param=x start=0 stop=1.8 lin=200 oppoint=rawfile maxiters=150 \ maxsteps=10000 annotate=statustran tran stop=300u write="spectre.ic" writefinal="spectre.fc" \ annotate=status infotimes=[0] maxiters=5 infoname=tran_Info finalTimeOP info what=oppoint where=rawfiletran_Info info what=oppoint where=rawfilemodelParameter info what=models where=rawfileelement info what=inst where=rawfileoutputParameter info what=output where=rawfiledesignParamVals info what=parameters where=rawfileprimitives info what=primitives where=rawfilesubckts info what=subckts where=rawfilesaveOptions options save=allpub. and so on ? As you said last time I also checked the DC sources value and time-zero value and they are equal. The answer could be: none, one single point, many pointsetc. So right now you're probably best doing this in Matlab, say. The final operating point also differs from that got fromplotting iM0 and iM1 and then see the current at time stop time of the two curves. I have struggled with it all night now. I would also try to do it automatically, like more or less what you made me do for "save.scs"Maybe include some "print.scs"? The OP function gets DC operating point data, not the results from a DCsweep, which are separately stored. It looks as though you want to run a certain number of DC operating point analyses (I'm not sure if this is fixed or could be variable) but you might want to run your steps in a loop (for, foreach, while) something like the following: The file name is generated depending on which iteration you are on. the Designer's Guide forum). If there is a way of doing it in Cadence, I would be glad to learn it. I thought they should be the same. // example of sweeping id curvesmodel nch mos1 type=n vto=1 kp=16u gamma=1.3 lambda=0.01 \ phi=0.7 pb=0.80 mj=0.5 mjsw=0.3 cgbo=200p cgso=350p cgdo=350p \ cj=300u cjsw=500p ld=0.1u tox=80n \ af=1 kf=3.1e-24m1 (drain gate 0 0) nch w=20u l=0.8uvgs (gate 0) vsource dc=2.5vds (drain 0) vsource dc=1voff (off 0) vsource dc=20mvcvs (gate2 off gate 0) vcvs gain=1rload (gate2 0) resistor r=10ksave m1:ids m1:gm rload:1sweepvgs sweep dev=vgs param=dc start=0 stop=2 step=20m { dc dc dev=vds start=0 stop=5 step=20m}. All the results there are well within the tolerances. The question I'd like to answer (in pictorial form) is: what are the (VGS,VDS) couples that give me a value of - say - 10 for my gm? Normally this doesn't happen for DC sweeps, just DC operating points - in order to prevent a huge amount of data being produced that most of the time you don't need. And ran (from command line) "spectre idcurvesw.scs" which produced idcurvesw.raw (the PSF results). Surely there should be a better (faster) way? (architecture assesment, chain analysis and the like)? I think you're looking at the tranOp results not the time=0 operating point information. With this video you will learn to run a DC simulation to find device threshold voltage, capacitance, etc. The key is that you're using the OP() function, whereas I said to use the results browser. Or click on the green play button on the right side of the ADE window. The print statement in spectre is primarily there for compatibility with other SPICE simulators, and is rarely used with spectre syntax (spectre -h print for more details; for example, it must have a comma at the end of all the outputs, which is a little strange). So if the two independent axes (VGS and VDS) are "x" and "y", you want a slice which is in the z axis - i.e. Regarding the 2.5s in interactive mode, I can send in something although this is a pretty long standing thing for as long as I can remember (back to IC 4.3 or 4.4 days). "Vth" == OP ("/M1","vth"). For example, if we have a dc simulation where voltage_dc_source is swept from 0 V to 1 V with step of 1m: analysis('dc ?dev "/voltage_dc_source" ?param "dc" ?start "0" ?stop "1" ?step "1m" ). Subsequent chapters explain how the Stimulus Editor is used to define custom analog and digital signals, how the Model Editor is You're really worried about 1 part in 40 million? This video shows DC simulation in cadence virtuoso. The tranOp results are coming from the: finalTimeOP info what=oppoint where=rawfile. I've enabled saving as much as I can in the Save All area. Cadence help The corners depends on the devices u have in ur circuit, For example , If u use transistors , resistors and capacitors , so u . Left-click dc and left-click on the box Save DC Operating Point 3. Analyses-> Choose. unfortunately the value() function doesn't provide what I am looking for. You can do this by adding a line "save M1.rout" (without the quotes) etc.., or put all such commands in a file and include it in the simulation. It is maybe not efficient in the long run but is certainly viable for the moment. I found in the result browser an "export" option which is giving you the data in csv format. Potentially there's a print statement in spectre, but I'm not sure that's really the right solution. And case 2 seems to be equal to 4, while case 1 seems to be equal to case 3. Hi,I looked into web and cadence manuals, but I cannot find the answer to my question. I was focussed in the save all parts and also digging in the spectre docs. If not, use the previous solution as initial guess. conditions, rather than solving for the quiescent operating point var name of an independent voltage or current source, any element or model parameter, or the keyword TEMP (indicating a temperature sweep). That appears to be the case here. However, I'm seeing something like 2.5 seconds per point with an ocean script which quite frankly stinks for a circuit with 1 transistor. After readingyour reply to another post in this forum where you mentioned the "spectreRF_workshop", I looked into it and found an high-level model of a Tx subsystem, but found not much information on the general subject of system level simulation. The OP function will retrieve the DC operating point data, not the results from the DC sweep. If I just put together some loops in ocean, it looks like spectre is indeed running in interactive mode (batch would be even slower). U don't able to plot Vth vs Vgs during DC sweep. Off the topof my head, you can probably get this via pv("/N1" "vdsat" ?result "dcSweep")or something like that but it's probably easier to look in the resultsbrowser. returns. I am interested in plotting some MOS DC parameters like gm, gmoverid, Cgg, gds as they vary across VGS and VDS. Want I would like to achieve is to save dc operating point for every step of dc simulation, where a voltage source is swept from one value to another with a given step. Please do Dan; it really shouldn't be this bad. There is a small amount of inaccuracy that appears in the DC solution with reltol=1e-3, which reduces if you tighten it to 1e-5 (note, I seriously doubt you need this level of accuracy for this circuit) - and if you compare the three operating points, they are very close: DC : M0:id = 0.00079999999976654 M1:id = 0.00079999999976654TRAN 0: M0:id = 0.00079999999976654 M1:id = 0.00079999999976654FINAL : M0:id = 0.00080000135675758 M1:id = 0.00079999851611377, openResults("forum_oppoint.raw");println(results());println(results(?noAlias t))selectResult("dcOpInfo")printf("DC : M0:id = %.14g M1:id = %.14g\n" getData("M0:id") getData("M1:id"))selectResult("tran_info-tran_info")printf("TRAN 0: M0:id = %.14g M1:id = %.14g\n" value(getData("M0:id") 0) value(getData("M1:id") 0))selectResult("finalTimeOP-info")printf("FINAL : M0:id = %.14g M1:id = %.14g\n" getData("M0:id") getData("M1:id")). The term "slicing" is probably not 100% correct (poor English I suppose :)). Newton Raphson) which iterate towards a solution and determine that the solution has converged when the error is small (this is all part of a tradeoff between speed and reasonable accuracy). I did simulations and I see that when dc operating point is saved for tran simulation (using "writefinal") and then is read by "readns" in dc simulation it helps to run the analysis faster. There are a fair number of blocks for certain types of systems - primarily for RF systems - so the Spectre RF documentation (User Guide and Theory) in the MMSIM documentation are a good place to look. So I would say you're worrying about a level of accuracy that really isn't warranted. line 6: the DC sweep statement. I actually get only one point, which is the point corresponding to the "static" value of VGS, in the design variables list. You are choosing all the values the DC sources which are used by the program to calculate the operating point. cadence region=2 saturation In ADE choose Results > Anotate > DC Operating Point then choose any MOS of which u want the op pt condition. The way to do this is to create an ASCII file called "save.scs" and in that put: (see "spectre -h save" for more details - particularly on wildcarding). After that open Choose Analysis=> dc =>Save dc operating point, then OK. Before finishing, run the simulation by pressing Netlist and run. There are two parts to the Matlab interfaces. If that returns "interactive", then doing the parametric sweep should be quick (assuming you're not running in distributed mode in ADE L). I found in that release, the infotimes output is in a result called "tran_info" and I can't plot the waveform (it is a single point waveform) but I can send the results to a table. save N1:vdsat. There's one which is an interface to Simulink - available with spectre and AMS Designer - which allow co-simulation with Simulink; and a toolbox to allow Matlab to read spectre/Ultrasim/AMS simulation results directly into Matlab for further processing. Regards, Andrew. On Thu, 18 Nov 2004 16:41:49 +0100, Svenn Are Bjerkem wrote: You do not have permission to delete messages in this group, Either email addresses are anonymous for this group or you need the view member email addresses permission to view the original message. However, is there a case where the difference is large (beyond the tolerances)? Riad. U need to set DC OP analysis, output variable e.g. Possible values are no and yes. I can do a parametric analysis, but the overhead of spectre starting and loading the netlist each time is pretty awful. The transient and DC operating points will be the same if the DC value of the sources is the same as the time zero value of the source. Under dc, choose "save dc operating points" and click "enabled" checkbox. 2. This operating point is independent on the sucseeding DC analysis (or ac analysis), which varies one of the DC sources (or any other parameter determining the DC current distribution). Thank you again for help. Cadence SKILL/Ocean loading and saving dc operating point every dc simulation uses the same input tran.fc file. That's one of the reasons for offering a co-simulation capability with Simulink. Yes - of course, the DC operating point is set by YOU. Transient analysis failures are usually due to model discontinuities or unrealistic circuit, source, or parasitic modeling. In other words: how many blocks, simulation types, evaluation toolsare available and easy to configure for this type of task? Mar 27, 2009 #3 P pnallahandi Newbie level 3 Joined Mar 14, 2009 Messages 4 Helped 0 Reputation 0 I'll later explore the system capabilities of the library and certainly come to the support if questions arise. Circuit simulators solve nonlinear differential equations. Thanks (that must be the eighth time I write it today). This means you'll need to plot the DC load line in order to determine the DC operating point of the transistor. Tran analysis: iM0=800.002uA and iM1=799.999uA. ", 1. analysis('dc ?dev "/voltage_dc_source" ?param "dc" ?start "low" ?stop "high" ?step "1m" ), 2. analysis('dc ?dev "/voltage_dc_source" ?param "dc" ?start "low" ?stop "high" ?step "1m" ?readns "tran.fc"), 3. analysis('dc ?dev "/voltage_dc_source" ?param "dc" ?start "low" ?stop "high" ?step "1m" ?restart "no" ), 4. analysis('dc ?dev "/voltage_dc_source" ?param "dc" ?start "low" ?stop "high" ?step "1m" ?readns "tran.fc" ?restart "no" ). Any change in the Q-point changes the slope of the tangent line. I then used the IC616 base release (I think it was an early IC616 ISR you were using). Star-Hspice supports source value sweep, referring to the source name (SPICE style). There's not really an capability to do that - there's the xval function if there's a single crossing, but if there are multiple regions that won't help you. There's no contour capability, although you can take a slice across the data using the value() function - so maybe that is sufficient. It is clearly visible that the simulation in case 2 is faster than in case 1 for next steps. Using DC Initialization and Operating Point Statements DC Initialization and Point Analysis 6-8 Star-Hspice Manual, Release 1998.2 Examples.NODESET V(5:SETX)=3.5V V(X1.X2.VINT)=1V.NODESET V(12)=4.5 V(4)=2.23.NODESET 12 4.5 4 2.23 1 1.OP Statement Operating Point When an .OP statement is included in an input file, the DC operating point of the Select dc as the Analysis type, select Save DC Operating Point, select Design Variable as the Sweep Variable, enter v_base in the Variable Name field, enter a start and stop value of 1 and 3 in the sweep range to sweep v_base from 1 to 3 volts. The process is easy as the relationship between Ic and Vce is given by Vcc = Vce + IcRc It works just perfectly. For dc sweep these values are not normally stored. However, if a parameter sweep, a .DATA statement, Then open the EDA or Analog Design Environment from tools menu. I totally missed the Select OP parameter in the To be saved section. 'analysisOrder list ("dc") ); envOption run () however in such a case, every dc simulation uses the same input tran.fc file. I do have another question, but it is a slightly different matter so I'll open a new post (after checking for the topic in the Forum). I can use a 'sweep' analysis in spectre and if I'm in ADE-L I can play games with puttting the 'sweep' analysis in a model file that gets included. Note that a DC sweep is not the same thing as transient analysis of a circuit. Left-click OK The AC analysis will sweep frequency from 1 GHz to 9 GHz with a step size of 1 MHz. Even if I had, the starting point for the two DC solutions may have been slightly different (it typically starts from whatever set of numbers were used previously - or it may have been that there was a small difference in the number of iterations - either way, the differences are well within the accuracy tolerances). does not get saved over a DC sweep. The transfer analysis can be combined with a dc sweep so that the transfer function is computed at each point over a range of bias conditions. Hence, the simulation should run even faster. It may be that my best choice is a nested set of 'sweep' runs in a command line spectre and then use python to grab out data from the spectre logfile. Could you not use the ability in ADE, Outputs->To be saved->Select OP parameters, and then you'll get the gm, gds or whatever you want to save versus your sweep variable in the dc sweep (rather than doing a parametric sweep across a dcOp)? For ac analysis, the dc operating point is automatically determined through an operating point analysis. I'm interested in being able to *quickly* simulate some device small signal characteristics versus some parameter (design variable, temperature, etc). No, not unless there is some circuit behaviour (such as something that hasn't settled in the duration of the simulation, or some adaptive non-periodic behaviour like a sigma-delta modulator) which means the beginning doesn't match the end. Now I only have to make the toolbox work in the environmentWich won't be difficult with the help of my super-duper CAD guys ;). How do you print dc operating point data of all components (Mxx) from the simulation result ? I didn't actually see that difference. I thought that in transient analysis the zero time and stop time points of current should be equal to the transient operating points of current at time 0 and stop time respectively. When you do a DC sweep, it does not save the operating point for each point in the sweep by default. I looked into manuals for "?restart" attribute, but I am not sure what it does. While we calculate new dc operating point for every dc step we could use them one after another for following dc steps as in the example above. What are you looking at which shows you there's a difference? Having done this, you should be able to access the resulting operating point data from the DC sweep from the results browser, and then you'll get a plot of it versus your sweep. This forward transconductance becomes defined by change in drain current divided by the change in gate-to-source voltage at a Q-point with the drain-to-source voltage (Vds) remaining at a constant value. Can you point me to the place in the manuals where this topic is explained? Left-click ac and fill out the box as follows 4. DC operating point for one step is closer to the ideal for following dc step, while initial tran operating point may not. In that, the results all 800.026uA (assuming you're looking at the id operating point parameter for these devices). Note I did this with MMSIM14.1 ISR18 so your results may be slightly different (although not significantly different). You could also just type the getData() expression into the calculator. start 2nd sweep4. Of course I could set up an equation in the Calculator for the derivative of Id but I think that "somewhere" the tool should calculate those parameters for meAnd also because for some trickier parameters like Cgg the whole process would be more complicated. However, when I run the transient analysis, then plot id and look at the id at time zero I got the result is a bit different: TRAN 0: M0:id =800.000005e-6M1:id =800.000005e-6. Left-click Analyses -> Choose 2. or tools->parametric analysis.->variable name: temp, sweep temperature if simulating with corner, tools->corners, it combines various temperatures and corners and runs them once . VP) resistor r=1KR3 (vdd! Pole-Zero Analysis Similarly could look at m1:ids: id=cds_srr('idcurvesw.raw','sweepvgs_dc-sweep','m1:ids')mesh(getfield(id,'vgs:dc'),id.dc,id.A). I've just checked operating points from two files as you said. The criteria used to determine the error is generally in the form reltol*quantity+abstol (so this might be the change between two iterations, or the error in the sum of currents into a node). I found following commands:- write- writefinal- readnsI can run .tran simulation with "?writefinal" attribute pointing to the file where .op of the circuit will be saved and then load it for dc simulation:analysis('tran ?stop "500n" ?writefinal "tran.fc")envOption( 'analysisOrder list("tran")); envOptionrun()()analysis('dc ?dev "/voltage_dc_source" ?param "dc" ?start "value_low" ?stop "value_high" ?step "1m" ?readns "tran.fc" )envOption( 'analysisOrder list("dc") ); envOptionrun() however in such a case, every dc simulation uses the same input tran.fc file. I think you were pretty clear and I should have implemented everything, but it isn't working yet. The idea is to create lists for each thing you want to sweep and the run it within nested foreach instructions. In general, you will have The transient response will arise if your circuit includes inductors and capacitors. However, there are two questions, could you explain? Does anybody know of a way of overcoming this? However, in my case, these files don't have current info. In general a dc sweep will re-use previous information as a starting point - you can't save a "nodeset" for each point and re-use a the next point. I would have added some screenshots inline in the post, but I couldn't find my way through. The operating point at time 0: iM0 and iM1 are not the same at the one I had by running transient and plot iM0 and iM1 and then see the current at time 0 of the two curves. The second field "dc" is required to specify the command. The difference you're seeing is purely down to the initial DC operating point - the ?readns is allowing it to compute the initial operating point based on the transient solution. I know it's not appealing to write one's first post in an RF focused group talking about DC but please bare with me :). I should be able to run 1000 points in a few seconds (or less) instead of almost an hour. Keeping VDS fixed for the moment, I would expect to be able to DC sweep VGS and get a curve of - say - gm Vs. VGS. Under ac, setup the sweep variable as frequency and choose the sweep range for the simulation. What you'd need to do is create an include file, with: in, and then use the results browser to access this information. run 2nd sweep6. To run simulation: Simulation-> Netlist and Run. I'm running dc simulation:analysis('dc ?dev "/voltage_dc_source" ?param "dc" ?start "value_low" ?stop "value_high" ?step "1m" )envOption( 'analysisOrder list("dc") ); envOptionrun()I would like to have faster convergence. A dc sweep with dc operating point enabled in ADE-L (or even just straight up spectre from the command line) only reports dc operating points (like gm, gds, etc) at the start point. reltol defaults to 1e-3, and vabstol is 1e-6V and iabstol is 1e-12A. I could swear I also looked in the results browser but of course if gm is here now, it must have been there last time as well :), I have a second part for this question however :-D. Now, to retrieve the behavior Vs. two variables, I have to do a parametric sweep (I suppose): DC sweep VGS, par sweep VDS. In a DC sweep, the circuit is in the steady state, meaning that you are examining the current and voltage throughout the circuit after the transient response has died out. Please look at the examples in your Cadence stream, they are very helpful ! You could use the spectre toolbox for Matlab (covered in the MMSIM documentation, and in app notes in the /tools/spectre/examples directory hierarchy). Operation Point Analysis in Cadence can gives u only one value for Vth parameter. The difference is not only in the first dc step calculations. Versus time using this approach run 1000 points in a three dimensional.... 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