2-fingers CMOS transistors in Virtuoso

[emont89]

Hello
I have a question about fingering. If I create a 2-finger transistor, it is possible to create it with the D-S-D configuration or only with the S-D-S configuration_ In the case it is possible, which is the option in Virtuoso to set it?

 

[kenambo]

two cases are possible.

you can use it according to your need because there is no difference fpr source and drain in layout point of view

 

[dick_freebird]

If your particular PDK allows permuteSD (or whatever
the LVS tool of choice likes to call it) and this is a simple
symmetric MOS (not extended-drain, LDMOS, etc.) then
there's no LVS difference and you don't have to set anything.
I found, though, in one Assura setup that this aspect needed
messing-with and was not very obvious. I forget the details
now. In a general purpose vanilla CMOS you would expect
this to be allowed by default.

However, that configuration (DSD) is worse for speed /
frequency response than SDS in a common-source amp
owing to the 2X larger D plate/sidewall capacitance. A
source follower might benefit, I suppose.

 

[hamletboy]

I hope in updated cadence you can see the option like "switch S/D" . Which mean we can switch the source and drain depending on the circuit .