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OPA847 PSPIC model issue
I downloaded the OPA847 PSPICE model from TI website. When imported into ADS I had the following warnings:
Creating schematic with named connections.Reading item definition file "C:\ADS2009/config\spctoiff.cfg"WARNING: Skipping unrecognized element type: line #176, "s_s1 3 4 1 2 _s1".WARNING: Skipping unsupported model type "vswitch", line #178.Element name .125 changed to x125Element name x128*1.005 changed to x128x1x005Translation completed at Wed Sep 23 15:38:41 2009.
I went ahead and try to simulate it anyway but got very low gain results even for simple unity gain test circuit.
I search for the solution on the internet and found the following thread on the TI forum.
For the OPA847, the typical problem in going to a non-Pspice environment is the model of this switch:
.model _s1 sw roff=1e9 ron=1m vh=3v vt=2v
We can remove the disable function by changing the following lines. This should allow for proper operation in ADS and possibly HyperLynx.
.SUBCKT OPA847_Model + - V+ V- Out
R_R1000 $N_0022 $N_0005 0.1
*X_S1 $N_0004 Dis $N_0022 $N_0005 OPA847_Model_S1
This last statement is commented out, but could be removed.
Also, remove this statement:
.subckt OPA847_Model_S1 1 2 3 4
S_S1 3 4 1 2 _S1
RS_S1 1 2 1G
.MODEL _S1 VSWITCH Roff=1e9 Ron=1m Voff=3V Von=2V
The new model would be reduced from 6 pins to 5 pins. Here it is in full:
I followed this suggestion and the model seems to work ok in ADS at least in term of gain. I wonder if someone could tell me whether this change is safe and it is not going to cause any other issues later.
The procedure in the post you referenced looks fine.
I have converted similar high-speed amp models for use in ADS and removing the switches is about all you need to do.
Please be aware that different simulators can give different sim results. That's just the nature of simulators.
Please let me know if you have any more questions.
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