Burr-brown Corporation

Burr-brown Research Corporation

Donald L Brumbaugh

Anthony D Wang

An integrated circuit digital to analog converter includes circuitry having first and second resistors in a R/2R resistor ladder which scales bit current contributions to an analog output current. Each of the first and second resistors have a respective terminal connected to the collector of a bit current transistor, the emitter of which is connected to the emitter of a waste current transistor. The digital to analog converter includes a metal ground voltage conductor having a 'shared node' and a distributed resistance between one side of the shared node and a main ground voltage connection. The collector of the waste current transistor and a second terminal of the first resistor are both connected directly to the shared node. In operation, the waste current transistor switches waste current into the shared node, rather than into a separate waste current ground conductor. This results in substantially less voltage variation across the distributed resistance of the metal ground voltage conductor, and consequently lower non-linearity, than is the case if waste current is switched into the separate ground conductor.

Circuit and method for reducing non-linearity in analog output current

A monolithic digital-to-analog converter integrated circuit is disclosed including a first plurality of more significant bit switches having scaled bit switch currents and including a second plurality of lesser significant bit switches, the output nodes of which are coupled to a ladder network which contributes a binary-weighted portion of each lesser significant bit switch current to the summed analog output current. First and second output conductors, separate and apart from one another, are used to couple the output nodes of the more significant bit switches and the output current of the ladder network, respectively, to the analog output current pad. First and second ground voltage pads are included for isolating waste current conducted by the more significant bit switches from currents returned by the ladder network to the ground voltage. The waste current nodes of the lesser significant bit switches are conducted to the same ground voltage pad that conducts the currents returned by the ladder network.

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Tucson, AZ, United States of America

Donald L Brumbaugh