I was reading through MOSFETS, and the most prominent parameter is drain source "on" resistance. I am unable to figure out what it is. suppose for a given gate source voltage V_GS we have applied a drain-source voltage which brings saturation to the MOSFET, at this point still the MOSFET approximately works as a resistor? if not what is the resistance between source-drain now? is source drain resistance is only applicable for the linear region only? or is it for any region?
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2\$\begingroup\$ When MOSFET is working in saturation he will be acting as a voltage-controlled current source (we use this region in CS amplifier for example ). But, when using MOSFET as a switch (triode region Vds < (Vgs - Vth) ) then we can use R_ds(on) resistance to find the Vds voltage and power dissipated by a MOSFET. \$\endgroup\$– G36Commented Mar 13, 2021 at 12:22
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the most prominent parameter is drain source "on" resistance. I am unable to figure out what it is.
Here's a MOSFET characteristic from wiki: -
Note where the saturation region is and now, if I focus on the linear region (not the saturation region), I can show various values of on-resistance in orange: -
Basically, on-resistance is the slope of each blue curve close to the origin of the above graph.
at this point still the MOSFET approximately works as a resistor?
It's not perfect but, providing your expectation of "linearity" isn't too high, then, in the linear region, it behaves like a voltage controlled variable resistor (where the slope of each orange line above is measured in ohms).
answered Mar 13, 2021 at 12:27