Conditionals

Gnucap behavioral modeling conditionals are an extension of the ``AC'' and ``DC'' Spice source parameters.

The extensions ...

1. There are more choices, including an ``else''.

2. They apply to all elements (primitive components).

3. 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.

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

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.