Bipolar - 4 terminals

[mvj]

Hi All,

I am using ams process and the bipolar in this has 4 teminals instead of 3. May I know what the 4th terminal is and where should it be connected.



The terminal on the top is collector
left side - base
bottom - emittor
what is the one in the middle?

Thanks a lot in advance!!
M

 

[Prototyp_V1.0]

Just another connection to base.

 

[dick_freebird]

I suggest you select & "q" (property edit) the extra terminal
and see what its name is. It could be the substrate node in
a JI process, in which case you have parasitic diodes and
caps that need representing.

 

[mvj]

Hi,

I have done the select & 'q' on that external terminal and it said taht it is SUB which should be the substrate if I am not wrong.

The process that I am using is a CMOS process with P-substrate and N-wells for the PMOS transistors. So the bipolar that I have is a parasitic pnp as shown in the below fig. (sorry for the bad drawing..). From the fig. we can see that the collector and the substrate are the same, so can be just short the two terminals?

Thanks a lot in advance!!
M

 

[FvM]

Sorry but this drawing can be hardly related to the first one. It's obviously showing something different, e.g. PNP instead of NPN transistor etc. Also I never heard of a parasitic transistor provided as a component.

 

[mvj]

my bad!!
even the PNP shown in the second fig. also has similar type of connections. A base, an emitter, a collector and a "SUB" in the center. So, from the fig, the SUB and the collector are the same, is it not?

Thanks a lot in advance!!
M

 

[mvj]

Dear All,

I managed to take a look at the layout of the same and it turned out that the SUB and the collector are one and the same.

However, there are few more types of Bipolars in which the collector and the substrate are not connected together, they are different. So, I think it is always better to have a look at the layout and determine what the terminals actually are.

Regards,
M

 

[dgnani]

if you take a look at your simulator equation manual e.g. the basic Gummel-Poon model, you will see that BJTs have a fourth optional terminal device, substrate being the fourth terminal if it is separate from the other terminals, it is mostly a leakage node; in vertical structures the collector has a (reversed) junction to substrate; in lateral structures, the junction to substrate if from base
Having a 4 terminal device symbol when the layout is actually 3 terminals makes for some strange LVS rules...

 

[mvj]

@dgnani,

True!! I happened to figure out all that after having a look at the layouts of these devices.

Cheers,
M