The basic circuit for the common-drain configuration or the source follower configuration is shown. As is evident from the figure no resistor is connected in series with the drain terminal. The voltage across resistor RS provides the gate-source biasing voltage. This configuration is similar to the common-collector configuration for the BJTs. Like the common-collector configuration, the common-drain configuration also offers high input impedance, low output impedance, nearly unity voltage gain and no input-output phase reversal.