Explanation of BJT ratio value in bandgap

[davidwong]

I read that BJT ratio is usally 8:1, 16:1 or 24:1 due to the layout.
not 3:1
why ???

 

[ppenday]

Re: BJT ratio in bandgap

we choose 8:1, 16:1, 24:1 for matching purpose. 1 BJT can be surrounded (think of square shape) by 8, 16, 24, etc., BJT'S but not by 3 BJT'S.

 

[davidwong]

Re: BJT ratio in bandgap

I understand 1:8 and 1:24.
why 1:16 ??

 

[eng_Semi]

Re: BJT ratio in bandgap

if u choose 1:16 the layout will be (X = dummy)
X X A X X
A A A A A
A A B A A
A A A A A
X X A X X

but i think 1:14 is better
A A A A A
A A B A A
A A A A A

u also may choose 1:2
A B A

 

[jluhzw]

Re: BJT ratio in bandgap

I have seen the ratio 1:5

 

[davidwong]

Re: BJT ratio in bandgap

I have seen the ratio 1:5

how to achieve 1:5?