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Why we need to connect the bulk of NMOS to GND and the bulk of PMOS to VDD?

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tran

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Hi all,
Can anybody tell me why we need connect the bulk of NMOS to GND and the bulk of PMOS to VDD?
Thanks
 

Bulk connection

to insure that the junction between the diffusion and the bulk is reverse bias so that we minimize the current in the vertical direction
 

Re: Bulk connection

because of functionality of transisitor and avoiding of forward biasing in normal operation
 

Re: Bulk connection

A simple understanding is that a parasitical diode exists between the bulk of NMOS and PMOS, so in order to insure this parasitical diode is reversed, connect the bulk of NMOS to GND and the bulk of PMOS to VDD. Pls see the below picture!
 

    R

    Ramya Rao

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Bulk connection

Because we don't want the unwanted vertical parasitical diodes to be turned on.
 

Re: Bulk connection

Thank you very much for all answer. Now, I understand this problem.
 

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