This question already has an answer here:

As requested, I am forking a question as continuity to my previous inquiry from:

Keysight's Advanced Design System users, what's wrong with this simulation?

As such, this is not a duplicate. It is done so that the progrssion of the discussion is not so hard to follow for the readers. Maybe you should start doing it here in SE -- linked posts.

Keysight DC Sweep Problem

Alright, so I here's the DC sweep from the problem of the previous post above. I'm not really sure if I set it up right, since I'm new with ADS.

Here's the new setup: enter image description here

Here's the output:

enter image description here

Doesn't seem to matter what I initialize VINMAG to be, it shows the identical plots. I can ignore VOUT for now, but why is VINMAG's plot always the same for any initialization? Probably a problem with variable declaration/initialization?

This can't be right.


marked as duplicate by Andy aka, Daniel Grillo, W5VO Feb 16 '16 at 18:53

This question has been asked before and already has an answer. If those answers do not fully address your question, please ask a new question.

  • \$\begingroup\$ Yes, thank you Andy for pointing that out, I could always count on you.... IT IS a duplicate. Well, somewhat... Read the very first sentence of the post. \$\endgroup\$ – kozner Feb 16 '16 at 13:50
  • \$\begingroup\$ This is just so we can progress with the discussion without the readers being thoroughly confused as to what's heads and tails. \$\endgroup\$ – kozner Feb 16 '16 at 13:51
  • \$\begingroup\$ OK, it could be a model problem. I notice that you have a magnetude not the transient voltage for vin. For now we will use just a sine wave source, 100Hz if fine, and plot transient results. Try making the DC level of the source higher, say 12V. \$\endgroup\$ – user1582568 Feb 16 '16 at 14:32
  • \$\begingroup\$ I don't know exactly what you meant, so I took it the make the DC offset a constant 12V, so to make that the common mode. Here's the output i.stack.imgur.com/2ikNl.png \$\endgroup\$ – kozner Feb 16 '16 at 14:47
  • \$\begingroup\$ I would prefer to see VIN.V on the plot, not the parameter VINMAG, which appears to be assigned to both ampliture and DC properties of the source. I would also plot the drain voltage too, just to verify that the source is operational. Plot the source and drain pin currents if the MOSFET. If VGS is varying and there is constant current through the FET, then I would suspect you have a bad model for the IRFZ44. Can your simulator print out a spice netlist, if so please post that. \$\endgroup\$ – user1582568 Feb 16 '16 at 14:56

Having looked at your results we see all the terminal voltages and the channel current, I suspect there is a fault in the model (or gmin in the simulator is set to an extreme value). To see if it is resistive (or a gmin) effect but the rest of the model is working, try ramping the input voltage all the way to 24V. If the output starts to ramp when vin gets to about 15V, then check settings. Try a different transistor model.

  • \$\begingroup\$ Turns out you can export the netlist. Not through the Netlist Translator, but throught Tools > Netlist Export. Though I'm not sure how SPICE compliant this is: i.stack.imgur.com/RBmas.png \$\endgroup\$ – kozner Feb 17 '16 at 4:45
  • \$\begingroup\$ I also ramped up the VIN up to 50V and set Vto = 0V: i.stack.imgur.com/yLgjx.png. You were right, it does turn on, but after 12.4V or so. I got this component from: $HPEEOFS_DIR\oalibs\componentLib\Analog_Parts_vendor_kit ($HPEEOFS_DIR being the installation directory). Maybe theres just one or two parameters not being filled in. Here's the list of params: i.stack.imgur.com/zsHXB.png \$\endgroup\$ – kozner Feb 17 '16 at 4:50
  • \$\begingroup\$ Also, I'm still looking for the Gmin in the simulation settings, but I can't find it. This page: edadocs.software.keysight.com/display/ads2011/… . Mentions a "P-N parallel conductance" under "Nonlinear Devices", but I can't find it in the program. \$\endgroup\$ – kozner Feb 17 '16 at 4:56

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