Substrate contact - RF Cafe Forums

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dipak

Post subject: Substrate contact Posted: Mon Dec 11, 2006 11:03 am

Captain

Joined: Tue Nov 14, 2006 7:21 pm

Posts: 9

Location: Nagpur(M.S)

In CMOS ckt, there is one extra terminal for substrate contact to each component.

Can you tell me the significance of this terminal in CMOS?

what should be the effect if we avoid this terminal?

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jom

Post subject: Posted: Fri Jan 26, 2007 2:53 am

Captain

Joined: Fri Jan 26, 2007 2:40 am

Posts: 14

Can you tell me the significance of this terminal in CMOS?

You don't actually have to ground the terminal but it should at least be tied to the CMOS Source termainal. The difference in connecting the sub-tie to ground vs. tying it to the Source would be a slight difference in the threshold voltage.

Of course if we are talking about a PMOS device then the tie would be connected to either the Source or the positive supply.

what should be the effect if we avoid this terminal?

The transistor won't work properly.

jom

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Stephen

Post subject: Posted: Wed Jan 31, 2007 2:22 am

Captain

Joined: Wed Jun 21, 2006 8:33 pm

Posts: 21

Location: Queen Creek, Arizona

In some process technologies, it is possible to avoid connecting the body, namely specific SOI (Silicon-on-insulator). Here it can also matter if you are depleted or fully depleted, either way it is defined by your process.

Generally (especially in a bulk CMOS process), Jom's statement is correct. If you do not connect it the device will not function properly.

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Posted 11/12/2012


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