The invention provides an electronic circuit, an electro-optical unit, and an electronic apparatus with a reduced data writing time. A final current-conversion circuit segment includes a first driving transistor and a first current-supply transistor with a gain factor k times that of the first driving transistor. Further, a current-conversion circuit segment includes a second driving transistor and a second current-supply transistor with a gain factor k times that of the second driving transistor. An intermediate current that is k times the data current Idata generated in the second driving transistor included in the current-conversion circuit segment is supplied to the first current-supply transistor in the final current-conversion circuit segment.