# JFET series switch

The picture shows a series JFET switch. Is r_d itself the load or does the load have to be attached at the port v_out? If the second one is true then what is the purpose of r_d? Can't we replace r_d with the load we want?

• There are three connection points plus earth in the left diagram and I'm unsure what the right diagram is meant to represent. – Andy aka Jan 17 at 15:09
• @Andyaka i'm sorry, let me edit the picture. – Sayan Jan 17 at 15:11
• @Andyaka it is edited now, these two figure shows equivalent circuits. – Sayan Jan 17 at 15:15

The only sensible option (without further context) is that $$\R_D\$$ is an attached load. It certainly cannot be part of the JFET because it makes no connection to ground. The Vout circle symbol is a little confusing but, I believe, it's just showing the point where you measure Vout.
$$\R_{DS}\$$ is typically the drain-source on-resistance of the JFET.