"Case" pin on 4-pin jfet or 7-pin dual jfet?

[Jussi]

Hey,

Some JFETs has a fourth pin wich is called "case" in the datasheet. What is it for? How I use that pin on a circuit with only 3 connections on the transistor? Should I ground it?

EDIT: I found this:

The four terminal would be required when the package is mounted on an isolated or a surface not grounded. A metal plate or chassis panel would function to dissipate heat away from the semiconductor within the package. However these surfaces may not always be grounded. Grounding the case helps to block noise from reaching the semiconductor within the metal case.

[R.G.]

Yes, if you have the option, ground it. It's a built-in shield.

It's really, really useful at frequencies over 240MHz.