Biasing Network and Resistor RG
Biasing Network (Rs and Cs): JFET is self-biased by using the biasing network Rs-Cs. Desired bias voltage is obtained when d.c. component of drain current flows through the source-biasing resistor Rs. While capacitor Cs bypasses the a.c. component of drain current.
Resistor RG: Resistor RG provides d.c. path for reverse-biasing of gate-source junction