How to Calculate the Drain-Source Resistance RDS of a JFET Transistor

The drain-source resistance, RDS of a JFET transistor is the resistance of the transistor across its drain-source terminal.

Calculating the Drain-Source Resistance, RDS

The formula to calculate the drain-source resistance RDS is:

Note: VGS,off and IDSS are typically the knowns. You can get their values from looking them up in a data table or on the package they came in.