Equivalent circuit of multiplying d.a.c. using R-2R ladder network

An equivalent circuit of a multiplying digital-analogue convertor using a switched R-2R ladder is derived. This circuit consists of dependent sources, output resistance and capacitance, all digitally controlled. For a controlled voltage attenuator the multiplying d.a.c. model has been used to ensure the correct compensation of the practical multiplying d.a.c./opamp system.