How to handle another source pin of transistor?(SOT-343)

[Kidney]

Hi, I'm a graduate student of physics, and it is my first time making a PCB.
In my PCB, I try to add current amplifier using HEMT transistor, ATF-34143, packaged in SOT-343

There is one Gate & Drain pin and two Source pins at SOT-343 and I am confused how I handle left Source pin. (Pad number 2 in the image)

I did not set Nets or no connections at Pad #2. It is Ok? Or, should I set Pad #2 to Ground Nets or connect Pad #4?

 

[dick_freebird]

You want to look at the die level detail. Two sources could be two
ends of a fat slab, or one could be "for drain current" and the other
"for gate driver Kelvin ground" with very different current capacities.

Since you are not actually using a gate driver I would say to just
tie them both to the output.

Now when you say "amplifier" I see a "source follower" which will
sure boost available output current, but not very linearly or at all
controlled (other than by what the load wants to take, at the
delivered output voltage).

 

[Kidney]

You want to look at the die level detail. Two sources could be two
ends of a fat slab, or one could be "for drain current" and the other
"for gate driver Kelvin ground" with very different current capacities.

Since you are not actually using a gate driver I would say to just
tie them both to the output.

Now when you say "amplifier" I see a "source follower" which will
sure boost available output current, but not very linearly or at all
controlled (other than by what the load wants to take, at the
delivered output voltage).

Thank you very much!