Because of the high maintenance needed to monitor and filter spammers from the RF Cafe Forums, I decided that it would
be best to just archive the pages to make all the good information posted in the past available for review. It is unfortunate
that the scumbags of the world ruin an otherwise useful venue for people wanting to exchanged useful ideas and views.
It seems that the more formal social media like Facebook pretty much dominate this kind of venue anymore anyway, so if
you would like to post something on RF Cafe's
page, please do.
Below are all of the forum threads, including all
the responses to the original posts.
Post subject: substrate terminal Posted: Mon Dec 18, 2006 8:10 am
Joined: Tue Nov 14, 2006 7:21 pm
what should be the effects if we dont connect substrate terminal to the ground in CMOS process?
Post subject: SubstratePosted: Mon Dec 18, 2006 12:33 pm
Joined: Wed Feb 22, 2006 3:51 pm
Not connecting the substrate to ground in a CMOS process would have differing results, depending on what it is connected to:
1. Nothing. A floating substrate will cause roughly one-half of the mosfets to operate improperly. Which half would depend on whether your process was N-well or P-well. (As an aside: when I covered for a professor during a sabbatical, I was able to watch the students try to find out why their labs weren't working - a lot of very strange effects showed up due to an open substrate connection.
2. Negative voltage (for a normally-powered chip): Unless Vdd(max) is exceeded, you'll only encounter problems if the substrate is inadequately bypassed.
3. Positive voltage: depending on the voltage, as you increase from 0 volts, you'll increasingly move away from proper operation until your design doesn't work.