Interpreting the value of transconductance shown in a MOSFET datasheet. Why was that particular value chosen to be shown?

Question

Context: I'm a beginner in electronics, self studying MOSFETS. I'm trying to understand why the manufacturer of this MOSFET decided to provide a single particular transconductance value in the datasheet. I would like to understand why the manufacturer decided to show only that value and the reason behind why that value was chosen on the datasheet over all the other possible values.

Given this datasheet, I see that the manufacturer has chosen to show me the following value for transconductance only:

As far as I understand it, the transconductance is the slope of a point in the transfer characteristics graph (the plot of Vgs and Id)

I went to the plots in the datasheet to find the point in the graph where the manufacturer decided to provide this value, using the following logic:

Given Vds and Id marked in the previous image for the transconductance, I deduce the Vgs used seems to be 2.5V using the plot on the left of the image. Then reading the transfer characteristic's plot (right) I see roughly that the transconductance seems to be the slope of the pink line, at the point where Id is 0.2A (as seen in the value for transcondunctance in the datasheet) and the Vgs is 2.5V as previously deduced using the other plot.

Why would the manufacturer choose to provide the transconductance at this particular point? Does he expect people to use that point as the bias point for amplifiers for some reason? Is there some other common aplication that justifies why would that be? is it special in some way? It would seem to me that choosing a point a little bit to the right would give a higher transconductance.

Answer 1

It is a typical working point.

You use MOSFET in one of two conditions:

1. as switch. \$R_{DS,on}\$ is important.

2. as variable resistor in a linear circuit, e.g. in a voltage regulator. It will be biased close to its turn-on gate voltage and \$V_{DS}\$ will be high enough to saturate the channel. The given value is the maximum small signal gain.

it would seem to me that choosing a point a little bit to the right would give a higher transconductance?.

While true, I would say that two aspects speak against this: First, the manufacturer provides this value as typical realiable value, while the real value can be better. So quoting a higher value would raise expectations and require better manufacturing control. Second, going any higher in \$V_{GS}\$ would also exceed the continuous drain current rating.