Digital to analog converter having separate bit converters

Abstract

This invention relates to a digital to analog converter in general and specifically to unitary or monolithic miniature digital to analog converters designed to be fully embodied on a single one-half inch module without requiring external converter components. The digital to analog converter comprises n binary current sources and n two-way switches, n being the number of input word bits. Each switch is driven by a bit input and its function is to steer the current of the corresponding source either into a summing line for output or into a dump line. A primary feature of this converter is the separation of all individual bit converter structures comprising a current source and steering means into two different groups. In this scheme, a first group of converter structures is used to convert the high order bits and a second group of converter structures is used to convert the low order bits. This arrangement allows the provision of different types of current sources for the different converter structures depending upon the accuracy required for each current source. Control inputs are provided for acting upon the steering means to generate reference levels to which an input analog signal in an A/D converter is compared. By this technique, the D/A converters of the present invention may be utilized in A/D encoding and an improved conversion accuracy of about zero is provided.