The present invention provides a high speed digital-to-analog converter (DAC), and components for a high speed DAC. One embodiment of the present invention provides a novel current switching circuit that surmounts parasitic capacitance of the circuit elements. In another embodiment, the DAC includes a novel built-in-test circuit, which allows tests of the DAC at high speeds. One feature of the DAC constructed according to the present invention, is that it enables direct digital synthesis of communication waveforms. This Abstract is provided for the sole purpose of complying with the Abstract requirement rules that allow a reader to quickly ascertain the subject matter of the disclosure contained herein. This Abstract is submitted with the explicit understanding that it will not be used to interpret or to limit the scope or the meaning of the claims.