This tutorial demonstrates the usage of the Analog Waveform window by running an example from the demo/spice/ directory.

The Analog Waveform viewer is specialized for visualizing and analyzing Spice simulation results and allows the user to navigate between simulation results and the simulated netlist. It facilitates the analysis of analog circuits by allowing to explore its structure as well as its electrical behavior.

The interaction between the Schem window and the Analog Waveform viewer is ensured by drag-and-drop. The Analog Waveform viewer also allows to annotate voltage values to the nets shown in the Schem window.

Loading Demo Examples

The example Spice netlists are located at <install>/demo/spice/. The corresponding simulation results can be found in the same directory next to the netlist file.

First select "Read Spice" from the toolbar and open the file <install>/demo/spice/analog/folded-cascode-ota.sp. After opening the Analog Waveform viewer via the toolbar or the Window menu select "Open File" in the Analog Waveform window toolbar and open the file <install>/demo/spice/analog/folded-cascode-ota.csv. The structure of the netlist appears in the Schem window while the structure of the simulation results is shown in the Analog Waveform window. A list of curves are shown in the browser on the left side of the Analog Waveform viewer. You can view the curve by using drag-and-drop.

Show a curve by using drag-and-drop from the browser on the left

Dragging items from the schematic to a plot window shows and highlights the corresponding curve. Dragging a curve from Analog Waveform window to the schematic shows the corresponding netlist component. Not all curves have corresponding netlist counterparts. If you highlight a net in the Schem window, the corresponding curve in the Analog Waveform window is automatically highlighted in the same color.

Show a curve by using drag-and-drop from the Schem window

Annotating Cursor Values to Nets

The Analog Waveform allows to annotate the active cursor values to nets in the Schem window. Make sure either "Net Attribute at wire" or "Net Attribute at pins" is checked in the Preferences dialog. Now select "Activate cursor mode" in the Analog Waveform toolbar. The values on the cursor will be annotated on the corresponding nets of the schematic. It might improve the visualization to regenerate the schematic view.

Mapping the Components of a Spice Netlist to Curves of Spice Simulation Results

To make sure that Spice netlist components can be interpreted as curve names, a mapping between circuit instances and the instances in the Spice output has to be defined. If possible, this mapping is computed automatically. However, in some cases the automatic computation might fail. In this case a dialog shows up to let the user define this mapping manually.

You can open the dialog by right-clicking on the file in the browser of the Analog Waveform window.

The mapping contains two fields. The "circuit instance" defines the elements to remove from a circuit component’s name. The "curve instance" defines the elements to add to this name.

For example the "circuit instance" might be defined as "TOP X1" and "curve instance" as "X2.X5". The circuit component {net TOP X1 X3 Vout} becomes "X3 Vout" by removing "TOP X1" and then "X2.X5.X3.Vout" by adding "X2.X5". As the circuit component is a net, the Analog Waveform viewer will try to find the voltage V(X2.X5.X3.Vout) and plot it if possible. The hierarchy separator used for the "circuit instance" is a space. The separator used for the curves is a dot.

The inverse procedure is used to map curve names to circuit component names.

The current mapping can be examined by dragging a curve or a netlist component to a text editor, terminal or the Console window.

Other Functions

The toolbar of the Analog Waveform window allows direct access to some additional functionality. The current plot window can be split into several sub-windows. New simple or post-processing tabs can be opened.