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Design >> Analog Design >> can mos gate connect to vdd or gnd directly?
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Message started by lhlbluesky_lhl on Mar 19^th, 2013, 5:47am

Title: can mos gate connect to vdd or gnd directly?
Post by lhlbluesky_lhl on Mar 19^th, 2013, 5:47am

can the NMOS gate be directly connected to VDD, or PMOS gate be directly connected to GND?
does it will have relibility issues? such as gate breakdown, etc.
usually, a series resistor will be used, what is the role of this series resistor?
thanks.

Title: Re: can mos gate connect to vdd or gnd directly?
Post by lhlbluesky_lhl on Mar 19^th, 2013, 6:59am

here is a symbolic picture, thanks.

Title: Re: can mos gate connect to vdd or gnd directly?
Post by raja.cedt on Mar 19^th, 2013, 7:13am

Hello,
that depends on the oxide breakdown voltage. But in general vdd is lesser than breakdown voltage. The purpose of the resister is to limit the current in case if they break due to ESD or in-case of fast spikes.

Thanks,
Raj.

Title: Re: can mos gate connect to vdd or gnd directly?
Post by threepwood on Mar 23^rd, 2013, 5:19am

For single oxyde devices in technologies below 90nm we (in our society) use to use -for more safety- a "tie-on" or "tie-down" logic cell (you'll probably find in your digital library).