What happens when in inverter pmos is connected to gnd/vss and nmos to Vdd?

[gunjang]

In an inverter we connect pmos to vdd, nmos to gnd...
wht happens if we do viceversa??i.e pmos to gnd or vss, and nmos to Vdd ? will it still function as inverter??If so why??

 

[DZC]

inverter 0.35u

It still function as an inverter,but with reduced sing at a level of Vth.

 

[kola]

Re: Related to Inverter

See picture...

 

[mdcui]

Related to Inverter

and if you have following logic gates driven by this inverter, leakage will happen...

 

[gunjang]

Related to Inverter

Hi..can you all pls elaborate, becoz wht my reasoning is-for pmos , if 0 volt is applied to gate , with vdd connected to source, then pmos turns on......so current will flow from source to drain......
but if instead of connecting pmos source to vdd , i connnect it to ground , then the current wont flow from source to drain as holes ( channel below)wont be flowing from source to drain in this case(source will be negative this time so no holes created there...so no flow of holes from source to drain....)...so pmos wont turn on....
Similarly , for nmos----- if gate is at 1 volt, and source is connected to ground , then nmos turns on...but if instead i connect the source to Vdd , then again current wont flow so nmos wont turn on...so ultimately it wont function as an inverter....
Plz tell me where m i going wrong ....

 

[Troy]

Re: Related to Inverter

You would destroy the inverter by turning on the body diodes of the mos devices.

 

[dinesh agarwal]

Re: Related to Inverter

will act as inverter but the high level will not be equal to vdd

 

[gunjang]

Related to Inverter

Can you pls explain why??

 

[ajaytronic]

Re: Related to Inverter

gungan,

you forgot basic concept of MOS, There is nothing source and Drain, untill u connect it to potential.
because MOS is symmetric device.
For NMOS, higher potential connected terminal is called drain & lower potential connected terminal is called source ( bcoz it gives electron ) & vice varsa for PMOS.

So If you interchange the connection of inverter, S & D will also interchange. I think its enough to do ur homework......... you will get correct answer.

 

[sandeep_torgal]

Re: Related to Inverter

Hi,

It will not work as a inverter but as a source follower.
The output will not swing from Vdd to Gnd, but it will be Vdd-Vtn to Gnd+Vtp

Regards,
Sandeep

 

[erikl]

Re: Related to Inverter

gunjang,
don't let you get confused: kola, ajaytronic and sandeep are right. See kolas drawings and sandeeps explanation.
Cheers, erikl

 

[sandeep_torgal]

Re: Related to Inverter

Hi,

Ok to add to this, I added a chain of source followers with same drive in 0.35u technology and simulated the netlist.
The output voltage at the fourth stage is saturating at 1.6V and am unable to understand why is it so. The voltage should have been 1V or so at that point.

Can somebody let me know if there are any other views.

Regards,
Sandeep