Cadence Schematic Simulation w/Spectre

We can use a pulse source (vpulse) from the analogLib library to test the transient response of the digital CMOS inverter. This will provide us with out time-variant input source.

1. If you haven't already, create the above schematic. Use Edit->Properties to set the properties on the vpulse source as follows:

This will create a pulse between 0V and 5V, with a period of 200ns and a 50% duty cycle.

2. Check and save your design. Design->Check and Save.

3. Start up the Analog Artist environment: Tools->Analog Artist. This will give you 2 new menus in the schematic window.

4. Choose Analog Artist->Simulate. This brings up the simulator initialization dialog:

Make sure that the simulator is set to spectreS. You may also choose to use cdsSpice, rather than spectreS, if you are more familiar with SPICE's convergence parameters.

5. Click OK on the form to bring up the Analog Artist simulation window:

6. Bring up the form to set your simulation environment: Setup->Environment...:

The Model Path tells Spectre where to find the SPICE models for your parts. This should be a directory containing .m files. For our MOSIS 2u process, this should read: /usr/local/cadence/local/cadence/mosis2uModels.

Click OK on this form.

7. Set the simulation type: Analysis->Choose. Click on the box next to Transient. Then set the range time for your simulation, along with the step time:

In the above example, we are performing a simulation from t= 0 to t=1000ns by 1ns.
Click OK on the form.

8. Next, tell Spectre which node voltages and terminal currents we wish to save. Choose Analysis->Outputs->Modify. In your schematic window, it will read "Modify Output List...":

To tell Spectre to save a voltage, click on the wire whose voltage you wish to have stored.
To tell Spectre to save a current, click on the terminal of the device who current going into that device you wish to have stored.

For example, in the above schematic, the voltages of In and Out are to be saved, as they are highlighted by clicking on the two wires.

9. Run your simultion: Simulate->Run. After a while, Spectre will respond that it completed successfully:

10. We now need to tell Artist which waveforms we wish to see, in this case In and Out. Select Results->Modify Plot Set->Modify... The schematic window will read "Modify Plot Set..." Similar to how you told Spectre which voltages you want to save (step 8), click on the voltages/currents you wish to have plotted.

NOTE: to be able to plot a waveform, you must have told Spectre to save its node/current data before you simulated it (step 8).

11. Show your waveforms: Results->Plot Transient. The waveform window will appear:

12. Right now, the waveforms are probably pretty hard to read, as the two waveforms (in and out) are plotted on the same axis. We can make 2 separate graphs by choosing Plot Options->Strip. The waveforms should now show that your inverter does indeed work:

We can use a dc voltage from the analogLib library to test the DC response of the digital CMOS inverter. We will sweep this source between Vss and Vdd.

1. If you haven't already, create the above schematic. The DC source does not need to have a DC voltage, it can be left blank (we will be sweeping it)

2. Check and save your design. Design->Check and Save.

3. Start up the Analog Artist environment: Tools->Analog Artist. This will give you 2 new menus in the schematic window.

4. Choose Analog Artist->Simulate. This brings up the simulator initialization dialog:

Make sure that the simulator is set to spectreS. You may also choose to use cdsSpice, rather than spectreS, if you are more familiar with SPICE's convergence parameters.

5. Click OK on the form to bring up the Analog Artist simulation window:

6. Bring up the form to set your simulation environment: Setup->Environment...:

The Model Path tells Spectre where to find the SPICE models for your parts. This should be a directory containing .m files. For our MOSIS 2u process, this should read: /usr/local/cadence/local/cadence/mosis2uModels.

Click OK on this form.

7. Set the simulation type: Analysis->Choose. Click on the DC button. Set the from, to and by fields (in this case, we will sweep from 0 to 5V by .1V) Next, set the source to sweep, click on select component, and then click on the DC source to be swept. The instance name of the DC source will appear on the form (in this case, V37):

Click OK on the form.

8. Next, tell Spectre which node voltages and terminal currents we wish to save. Choose Analysis->Outputs->Modify. In your schematic window, it will read "Modify Output List...":

To tell Spectre to save a voltage, click on the wire whose voltage you wish to have stored.
To tell Spectre to save a current, click on the terminal of the device who current going into that device you wish to have stored.

For example, in the above schematic, the voltages of In and Out are to be saved, as they are highlighted by clicking on the two wires.

9. Run your simultion: Simulate->Run. After a while, Spectre will respond that it completed successfully:

10. We now need to tell Artist which waveforms we wish to see, in this case In and Out. Select Results->Modify Plot Set->Modify... The schematic window will read "Modify Plot Set..." Similar to how you told Spectre which voltages you want to save (step 8), click on the voltages/currents you wish to have plotted.

NOTE: to be able to plot a waveform, you must have told Spectre to save its node/current data before you simulated it (step 8).

11. Show your waveforms: Results->Plot DC. The waveform window will appear:

You will see two waveforms, In and Out, both plotted versus the sweep variable (In).

We can use a dc voltage from the analogLib library to set the DC bias point. (from the results of the previous section, we can see that a bias of 2.2V will work) We then give the source an AC magnitude of 1, and a phase of 0.

1. If you haven't already, create the above schematic.

2. Check and save your design. Design->Check and Save.

3. Start up the Analog Artist environment: Tools->Analog Artist. This will give you 2 new menus in the schematic window.

4. Choose Analog Artist->Simulate. This brings up the simulator initialization dialog:

Make sure that the simulator is set to spectreS. You may also choose to use cdsSpice, rather than spectreS, if you are more familiar with SPICE's convergence parameters.

5. Click OK on the form to bring up the Analog Artist simulation window:

6. Bring up the form to set your simulation environment: Setup->Environment...:

The Model Path tells Spectre where to find the SPICE models for your parts. This should be a directory containing .m files. For our MOSIS 2u process, this should read: /usr/local/cadence/local/cadence/mosis2uModels.

Click OK on this form.

7. Set the simulation type: Analysis->Choose. In this simulation we will sweep the frequency from 10Hz-1Gig.

Click OK on the form.

8. Next, tell Spectre which node voltages and terminal currents we wish to save. Choose Analysis->Outputs->Modify. In your schematic window, it will read "Modify Output List...":

To tell Spectre to save a voltage, click on the wire whose voltage you wish to have stored.
To tell Spectre to save a current, click on the terminal of the device who current going into that device you wish to have stored.

For example, in the above schematic, the voltages of Out is to be saved, as it is highlighted by clicking on the Out wires.

9. Run your simultion: Simulate->Run. After a while, Spectre will respond that it completed successfully:

10. We now need to tell Artist which waveforms we wish to see, in this case Out. Select Results->Modify Plot Set->Modify... The schematic window will read "Modify Plot Set..." Similar to how you told Spectre which voltages you want to save (step 8), click on the voltages/currents you wish to have plotted.

NOTE: to be able to plot a waveform, you must have told Spectre to save its node/current data before you simulated it (step 8).

11. Show your waveforms: Results->Plot AC. The waveform window will appear:

As we set the input source to have an AC magnitude of 1, the output transfer function Vout/Vin is simply Vout, as plotted in the above waveform.