A field effect transistor current mode differential logic circuit comprising load transistors for converting the current output of each differential leg current to voltage output, and means for configuring the bulk of each differential leg's load transistor to be connected to the drain of the load transistor for use the logic circuit in Subthreshold Source Coupled Logic (STSCL) mode, and means for configuring the bulk of each leg load transistor to be connected to a voltage or to source of the same transistor for use in MOS current more logic (MCML) operation.

A semiconductor apparatus may include a mode control circuit configured to output differential output signals which swing in a current mode logic (CML) area and a first control signal, in response to a power-down mode signal; a first circuit unit configured to be provided with the differential output signals, and operate in a power-down mode; and a second circuit unit configured to be provided with the differential output signals, and be interrupted in its operation in the power-down mode.