4.1 Conditionals
Gnucap behavioral modeling conditionals are an extension of the “AC”
and “DC” Spice source parameters.
The extensions ...
- There are more choices, including an “else”.
- They apply to all elements (primitive components).
- Each section can contain functions and options.
The following are available:
- AC
- AC analysis only.
- DC
- DC (steady state) value.
- OP
- OP analysis.
- TRAN
- Transient analysis.
- FOUR
- Fourier analysis only.
- ELSE
- Anything not listed.
- ALL
- Anything not listed.
A value or function with no conditional keyword is equivalent to ALL. For SPICE compatibility, use only DC, AC, or nothing.
They are interpreted like a “switch” statement. In case of a
conflict, the last one applies. A set of precedence rules applies
when some keys are missing. It is SPICE compatible to the extent the
features overlap.
The following table describes the precedence rules:
- OP analysis
- OP, DC, ALL, TRAN, 0
- DC analysis
- DC, ALL, OP, TRAN, 0
- Transient analysis
- TRAN, ALL, DC, OP, 0
- Fourier analysis
- FOUR, TRAN, ALL, DC, OP, 0
- AC analysis, fixed sources
- AC, 0
- AC analysis, other elements
- AC, ALL, 0
4.1.1 Examples
- V12 (1 0) AC 1 DC 3
- This voltage source has a value of 1
for AC analysis, 3 for DC. OP, Transient, and Fourier inherit the DC value.
- R44 (2 3) OP 1 ELSE 1g
- This resistor has a value of 1 ohm
for the “OP” analysis, 1 gig-ohm for anything else. This might be
useful as the feedback resistor on an op-amp. Set it to 1 ohm to set
the operating point, then 1 gig to measure its open loop
characteristics, hiding the fact that the op-amp would probably
saturate if it was really left open loop.