Emitter area multiplying factor in Hspice simulation

[jacobliu]

area bjt simulation hspice

Hi,
In hspice BJT simulation, there is a parameter "AREA".

Here is the description of this parameter in hspice manual:
Emitter area multiplying factor which affects currents,
resistances and capacitances. Default = 1.0.
&
The AREA parameter, the normalized emitter area, divides all resistors and
multiplies all currents and capacitors.

I have a vertical BJT spice model, the emitter area is 5*5, the base area is 11*11.
What is the value should i use in hspice simulation?
or,it is not a critical parameter in bandgap reference simulation?

Regards,

 

[ambreesh]

emitter area

The model for pnp 5*5 will be used from your model file.
The required parameter will be passed to the HSPICE simulation engine.
Do not bother your self with it

 

[jacobliu]

emitter area inhspice

The model for pnp 5*5 will be used from your model file.
The required parameter will be passed to the HSPICE simulation engine.
Do not bother your self with it

Hi ambreesh,

You mean that "AREA" is not a meaningful parameter for BJT simulation.
It doesn't like "AS" "AD" have some meaning for MOS simulation.
When we use "Qxxx E B C S modelname m=1", hspice will properly export BJT property from foundry.
that's right?

regards

 

[ambreesh]

bjt spice area scaling

If you are using multiple finger for it say 8 PNP in parallel yopu have to pass the mutiplying factor in the hspice netlist.
If it is only one then HSPICE will pick the model from your model file and not use its default parameter. So you need not pass any extra parameters.
Also depends on the syntax for the HSPICE for the BJT. If the syntax requires you to pass the area information then you have to, else not.

 

[hung_wai_ming@hotmail.com]

normalize area for hspice bjt

jacobliu,

I think what ambreesh said, is that normally when we use BJT in spice model, we have already restricted to the categories the spice model can provide. Normally, it may have emitter area of 5x5, 3x3, 10x10, and they are all being characterized by the foundy and the layout is also fixed to use, so we can't change and if change, the model may not be useful. So, just use the one provided by the model.
If you want to understand more about your BJT, you may check inside the spice model parameters.

 

[jacobliu]

layout of pnp5

Hi ambreesh & hung_wai_ming@hotmail.com,

thanks for your reply,

I explain why i submit this topic.

In hspice manual:
The scaling of the DC model parameters (IBE, IS, ISE, IKF, IKR, and IRB) for
both vertical and lateral BJT transistors, is determined by the following formula:
ISeff=AREA*M*IS
Ic & Ib are ISeff correlative factor.

This means the paramater "AREA" will affect BJT dc operation point.

In hspice manual:
AREA:Emitter area multiplying factor which affects currents,
resistances and capacitances. Default = 1.0.
AREAB:Base area multiplying factor that affects currents,
resistances and capacitances. Default = AREA.
AREAC:Collector area multiplying factor that affects currents,
resistances and capacitances. Default = AREA.

We can see BJT's gds from foundry clearly.Emitter area is not equal base area and it isn't satisfy hspice default setting.

In calibre LVS:

We need set AREA=25 for pnp5*5 to make LVS correctly.

It confused me the parameter "AREA" is useful to match foundry's measurement or not.

regards,

 

[godcadence]

spice,manual,bjt,area

The AREA parameter is an area factor that works on the model dc parameters. If you got the foundry's model and set the AREA to 2, then all the dc parameters in
the model will be set to the AREA*2's transistor. You may do a simple simulation to verify it.