Problem with CMOS inverter (power supply issues)

cmos inverter

hello

i have the cmos inverter and over it the pmos key switches the supply (3.3V) for the inverter.

the well of the inverter's pmos is connected to supply (3.3V) and the inverter's input is connected to 5V.

what happens then ?

if switch is on i have more than 3.3 V on it's drain and strange currents

regards

Re: cmos inverter

Hi,
Send the schematic of the circuit.

cmos inverter

No. The input (source)/Nwell diode will be forward-biasd.

cmos inverter

I think the gate oxide will be broken

Re: cmos inverter

If only the invertors input is connected to 5V, then this invertor will function sort of properly with the output pulled to 0V. However the pmos will be in accumulation and you are over stressing the gate oxide of the nmos. The ground bounce should be intereesting too. It should not break the oxide - a 3.3V gate oxide will stand 7V unless its crap. But if you continue to operate the invertor, the oxide will wear out faster and no Fab would sanction this kind of abuse.

The question is, where is the 5V coming from ? The output of another 3.3V invertor? This is a definite no! If you are trying to convert 5V logic to 3V logic then use a conventional down shifter schematic.

Anyway the real question is: do you know how long it takes to get that we invertor from the sparkle is some designers eye, to your bench? The tender loving care during its fabrication, the tears! the joys!......

and then you whack it with a hammer!!!!!

I think mos abuse should be a criminal offence.

Re: cmos inverter

that means you says supply is 3.3v and input is 5v then what happens if it will connects i think there nothing will b happened as some threshold voltage drop will get across nmos

Re: cmos inverter

can you send the schematic

cmos inverter

i'm not sure but i think if you apply 5V, then the overdrive voltage of the device will be too big, so the drain current of the device will be too big, and so it will pull too much current from the 3.3V supply, so the power consumption will be too big and the device will probably get hot, or even be damaged.