strong and weak mosfet

[sudhachocky]

Hi,
What is the difference between strong and weak mosfet? How do we differentiate whether mosfet is strong or weak?

Thanks in advance,

 

[prestonee]

you are being a bit vague, you could be referring to its operating condition, weak inversion or strong inversion. or weak drive vs strong drive.
I will assume you are referring to inversion. strong inversion is basically when the device is in saturation. weak is when it is acting in sub-threshold region.
vgs>vt and vgs<vt. both require vds >vgs-vt

-Pb

 

[sudhachocky]

Thanks for the reply

I want to know "weak drive vs strong drive" actually.
Can you please address this.

 

[Junus2012]

still the same answer of prestonne

Hi,
What is the difference between strong and weak mosfet? How do we differentiate whether mosfet is strong or weak?

Thanks in advance,

 

[prestonee]

When referring to drive, this could be seen a few ways, driving the mosfet, or the mosfet driving a load. weak gate drive would be related to the input signal directed at the mosfet gate is not able to sink the current fast enough to charge the Cgs cap of the mosfet resulting in a slower switch time then desired. If the Mosfet has weak drive strength, it would be in reference to the devices ability to drive the load, this would exist in both analog and digital(analog single transistor amplifier not able to sink the current needed for the loading while preserving the voltage, or the digital buffer that has too much cap loading on its output and therefore takes too long in the rise/fall times)

-Pb
typically weak and strong is in reference to inversion though.