can dummy transistor AD=0 or AS=0?

[angela.green]

hi,
might be really silly question to some of you. when will dummy transistor's

Area of drain =0 or Area of Source=0

I know dummy transistor are shorted, but in what kind of situation will the above appear?

Thanks

Added after 10 minutes:

can anyone help me on this? Would be sooooooooo............thankful!

 

[JoannesPaulus]

if the areas of the drain and source are 0, you have two possibilities: there is no transistor or you are using some default values.

 

[dick_freebird]

I always see these defaulted to 0 in my PDK, but there
are params for the LD/LS and deltas, and W of course
is known so Spectre can calculate the areas and peripheries.

 

[angela.green]

thank first for you guys' answer. but actually I want to know when will IN_S==0 or IN_D==0 in the following calibre xrc extraction. Someone told me that it happened when it has dummy transistors, but how come IN_D =0? Is it for the dummy transistor? or is it happened for normal transistor? Thanks again!


DEVICE MP(P) pgate POLY PSD PSD WEL <PDIFF>

DMACRO MOSPROP DEVICELAYER PIN AUX1{
[Property W,L,AD,AS,PD,PS
W=PERIMETER_COINCIDE(DEVICELAYER,PIN)/2
L=AREA(DEVICELAYER)/W
IN_D=PERIMETER_INSIDE(D,AUX1)
IN_S=PERIMETER_INSIDE(S,AUX1)
IF(IN_S==0){
AD=AREA(D)*W/IN_D
PD=PERIMETER(D)*W/IN_D-W
AS=AD
PS=PD
}
ELSE
IF(IN_D==0){
AS=AREA(S)*W/IN_S
PS=PERIMETER(S)*W/IN_S-W
AD=AS
PD=PS
}
Else{
AD=AREA(D)*W/IN_D
PD=PERIMETER(D)*W/IN_D-W
AS=AREA(S)*W/IN_S
PS=PERIMETER(S)*W/IN_S-W
}
]
}

 

[JoannesPaulus]

It depends on how the PERIMETER_INSIDE function is defined. If layer AUX1 is missing, it might return a 0, but I am just guessing here...

 

[angela.green]

the perimeter_inside is the standard Calibre's build-in function

The format is:
PERIMeter_INside(pin-or-layer, pin-or-layer)
Returns the total length of the parts of perimeters on the first pin
or layer that lie strictly inside shapes of the second pin or layer.