Ron in Saturation region

[vbhupendra]

Wat is the expression of Ron in saturation region ? or how to calculate it in saturation region ?

 

[Lord Loh.]

I do not think the saturation region can be calculated. the β of the transistors vary so much... You will have to see the Vce v/s the Ic plot to determine the base current value to decide the saturation region.

 

[suria3]

Hi,

Pls specify the Ron for MOS or BJT. Ron or the effective output impedance of the MOS can be calculated by plotting the Ids vs Vds curve. The slope of the graph with the inverse will give you the Ron in the saturation. By formula Ron = 1/ λIds.

Thanks,
Suria

 

[surianova]

Hi,

Pls specify the Ron for MOS or BJT. Ron or the effective output impedance of the MOS can be calculated by plotting the Ids vs Vds curve. The slope of the graph with the inverse will give you the Ron in the saturation. By formula Ron = 1/ λIds.

Thanks,
Suria

Because the current in saturation almost constant when Vds change, it will not get linear relatinship between current and voltage. so, it is not realistic to count Ron
in saturation region.

 

[suria3]

Hi Surianova,

As you said, in saturation region current , Ids will be constant for even Vds change, but since the existence of short channel effect/lambda effect, anyhow you won't flat curve. So, the value of Ron could be measureable as I stated. Other's opinion are welcome. Correct me if im wrong. Thanks Surianova.


The slope which gives, λ= 1/Ids*ΔIds/ΔVds. So, i guess once we get the slope value which is λ, the we can calculate the Ron = 1/λIds by knowing the Ids current.

Thanks,
Suria

 

[rjshmadala]

Hello Suria3,

The equation (Ron = 1/λIds ), u have given is valid when we consider channel length modulation.(i.e) the resistance when pinchoff occurs.at pinchoff drain current is more than in saturation .so i think u r statement on resistence at saturation is not valid . and morever the symbol u used is not corect. u should use (ron) instead of (Ron)

Regards
Raj