Mosfet: Why Saturation Mode?

[salil87]

Hi
Why do we always bias a mosfet in Saturation mode? Is it becaus gm is more in saturation or is it because gm is more linear in saturation?

Thanks
Salil

 

[Audioguru]

"Saturation Mode" for a Mosfet is very confusing because it is the opposite to a bipolar transistor.
When a Mosfet is saturated it is turned on a little so it is linear. It should be called Amplifier.
When a Mosfet is turned on hard as a switch it is called "Linear Mode". It should be called Turned On Hard.

 

[Venkadesh_M]

Hi
Why do we always bias a mosfet in Saturation mode? Is it becaus gm is more in saturation or is it because gm is more linear in saturation?

Thanks
Salil

Because all the time we are using it as a switch...

 

[keith1200rs]

Because all the time we are using it as a switch...

That isn't correct. Saturation mode (also known as "active") in a MOSFET is used when it is an amplifier. Ohmic (also known as "linear" or "triode") is normally used when it is a switch.

https://en.wikipedia.org/wiki/MOSFET

Keith

 

[Venkadesh_M]

yeah i am mistaken A mosfet saturations occurs for all its Vg (gate voltage) values But in a BJT it occurs as Ib is more than a certain value (max IC), so that is the difference in the measures thats why a mosfet is operated in a saturation mode in an amplifier...

In a mosfet

In a BJT