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A question about guard rings of PNP transistors

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reneezl

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Hi,

I had a question about the PNP transistor array:

Those pnp transistors are used in the bandgap reference circuit, and when the pnp array is laid out, should I add double guard rings to them? I mean, is this neccessary?

Thanks.
 

hi reneezl,

no it is not neccessary. It is a good idea to add a n-type guard ring for PMOS transistors, this way they will be protected from horizontal currents, that may interfere with their work. Double guard ring is double protection, you surround n-type guard ring with a p-type guard ring, so as i said u get double protection, but this will take much space. In conclusion it is not a must thing, it gives more protection to your transistors, but it takes more space. Hope the answer is clear.

Good luck, Shlapenka.
 

Hi Reneezl,

Depend what kind PNP you are using if you are using vertical PNP or lateral PNP device. then doule isolation ring would needed.
 

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