Help me out with layout of 8:1 pnp bipolar pair

[pugongying]

I want to layout the 8:1 pnp bipolar pair,and arrange them in 3X3 square,since all of the bipolars' collector and base are connnected to ground,I use metal 1 to connect them all,and I use metal 2 to connect the emitter of the outer 8 bipolar in a circle,also use metal2 to connect the central bipolar.

I wonder whether I can use metal 1 in four directions OR I should avoid parallel layout of metal 1 and metal 2?

Thanks very much!

 

[panyi]

Re: layout of bandgap

I'm not sure which is better.
But in my chip, I use metal 1 to connect GND and metal 2 connect the emitter the tapout reslut is ok.

 

[leo_o2]

layout of bandgap

Don't have cycle for 8 outer pnps. Keep metal2 for 8 outer pnps and metal2 for inter pnp paralled for connections so that the invironment will be similar.

 

[smilodon]

Re: layout of bandgap

Please study the picture i uploaded. Do not worry about the metal layer, it is not so sensitive.

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[ajaytronic]

layout of bandgap

smilondon,

This is good bjt example, but what I feel, If We can use M3, then connect all outer emitter with M2( Make a ring) & take center emitter connection with M3. This will give more symmetrical routing give good centriode matching. Even you can observe the improved result with simulation.

 

[wang816449]

Re: layout of bandgap

You make one like what you see in figure 2 on this site
**broken link removed**

 

[xhmv]

layout of bandgap

Smilodon, I am a new guy in analog design. So what u provide here is great, thanks.