22_custom_sym: creating a custom symbol
Scope
Create a custom diode symbol with an embedded (inline) model card.
The schematics
Click the image to get the sch-rnd sheet; also requires this project.lht in the same directory
Preparing for simulation
Draw the symbol the usual way, using lines, rectangles and {p t}
for placing terminals; select the objects, convert selection to symbol;
set the usual attributes (e.g. name on the symbol and on the terminals).
For spice simulation, set the following attributes:
- symbol attribute spice/prefix to D: for the simulation
this is a diode; this attribute lets the sheet name the symbol U1
still show spice a D component by prefixing the name with D_.
- symbol attribute spice/model_card to
.MODEL my_diode D (IS=2f RS=3.4 N=2.2):
this is how the model is specified inline, within the symbol, not
relying on external libs
- terminal attribute spice/pinnum; the positive (anode) terminal
should be 1, the negative (cathode) should be 2.
The inline model card option is useful for one-off symbols or for an easy
and quick way of tuning model parameters in test-bench schematics.
Simulation settings are similar to those used in
10_bjt_amp_tr, except for
modifications: instead of using modifications, this circuit has a voltage
source symbol.