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Hi

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 x125

Element name x128*1.005 changed to x128x1x005

Translation 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.

Hello,

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

.ends OPA847_Model_S1

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.

Quang