A current supply circuit providing a data line with a current corresponding to a digital signal composed of data bits includes a current control circuit, a precharge switch and a precharge regulating circuit. The current control circuit responds to control signals reflecting respective data bits to control the amount of current along the data line. The precharge switch precharges the data line to a predetermined voltage prior to current supply. The precharge regulating circuit exchanges with the data line electric charge corresponding to the control signals to move the voltage on the data line closer to a steady voltage corresponding to the data bits. In this way, an analog current corresponding to digital data can be promptly produced.