Leakage in gate of mosfet switch

[WillMakeItHappen]

Hi all,
I am using a nmos transistor as switch, it does not pass all the current from one side to the other. Is this normal ? has this happened to any of you ? The difference of current seems to be flowing into the gate of the switch...
Any comments/suggestions on this problm ?
Thanks

 

[barry]

MOSFETs don't have "sides"; they have a SOURCE and a DRAIN, and you'd better hook them up with the proper polarity!

Is it hooked up properly? Is it defective?

The gate should be more positive than the source(when it's on) , and the drain should be the most positive point in your circuit.

 

[dick_freebird]

Some MOSFETs have gate ESD protection. All MOSFETs
have finite gate tunneling current. Some of this may be
modeled (if this is a simulation problem) or physically in
play. Gate ESD damage is also common unless care is
taken and that would be a source of higher gate conduction.

 

[barry]

You don't say how much of a difference between drain and source current. 1%? 50%?

 

[crutschow]

Show your circuit diagram.

 

[WillMakeItHappen]

You don't say how much of a difference between drain and source current. 1%? 50%?

It's 2.5%, is this normal ?

- - - Updated - - -

I'm afraid i cannot show the circuit diagram. It's just a pmos current source followed by the switch, the load is a capacitor

Show your circuit diagram.

 

[crutschow]

....................

I'm afraid i cannot show the circuit diagram. It's just a pmos current source followed by the switch, the load is a capacitor

All you need is draw a simple circuit diagram and post it. I can't give you good advice if I have to guess at what your circuit looks like. "pmos current source" doesn't tell me how it's connected.

 

[timof]

Basic MOSFET has four terminals - drain, gate , source, and bulk.
"Normally", gate and bulk currents have to be low - in which case, source current should be equal to drain current.
If they are not equal - the current is flowing either to bulk (e.g. impact ionization current at drain), or gate (gate tunneling).

In technologies before 90 nm node, gate current is usually very small.
At technologies starting from 65nm node, gate tunneling current can be significant.

Max
----------