Raytheon Company

Analog Devices,inc.

John Memishian, Jr

Bertram J Goldstone

An analog-to-digital converter of the successive-approximation type including a digital-to-analog converter (DAC) comprising a plurality of independently-switchable current sources producing identical currents and connected to respective junction points of an R-2R ladder network. The common ladder terminal is driven by an operational amplifier so that the potential of the common terminal tracks that of the ladder output terminal. The ladder common terminal is connected to a comparator together with a sense ground lead. The output of the comparator is directed to bit sequencer circuitry which controls the switching of the DAC current sources to effect a match between the analog input current and the ladder output current.

Analog-to-digital converter with controlled ladder network

An analog-to-digital converter is adapted to operate with input signals having relatively large signal level variations, with the mean level of such signal centered at the midpoint in the operating range of the converter. The converter includes a series of cascade encoding stages, each one providing a digital output signal and a residue output signal, the latter such signal being passed as the input to the succeeding encoding stage. Each one of the cascaded encoding stages includes means for producing an analog residue output signal having a linear relationship to the analog signal applied to each such stage in the middle region of the operating range of each such stage. Such means includes a pair of amplifiers having diode-resistor feedback arrangements.

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Arlington, MA, United States of America

John Memishian, Jr