Digital to Analog Converter Circuit
A Digital-to-Analog Converter based on Resistive Interpolation Load
Prof. Sameer Sonkusale at the Electrical and Computer Engineering Department at Tufts has developed a single chip integrated DAC using resistive interpolation (RIDAC) at the output branch of a multi-input operational amplifier. Digital-to-analog conversion is a key element in driving LCD displays, sensors and actuators and traditionally resistor string DAC (RDAC) architectures have offered excellent linearity in the response given the low operation speed of these applications. However, conventional RDAC is unsuitable for high-resolution applications since the number of the resistors and switches increases exponentially resulting in large area footprint and slower speed. In addition, a large number of unit resistors compromises response linearity as well.
To address these issues, Prof. Sonkusale created a resistive load interpolation approach for high-resolution resistor string DAC using a multi-input operational amplifier serving as a buffer. To avoid the loading effect on the coarse resistor string, the interpolation amplifier converts the coarse voltage from the coarse resistor string to current for interpolation. Therefore, there are no additional buffers needed between the coarse and fine resistor strings. The significance of this resistive load interpolation approach is that it utilizes the built-in linear relationship between the voltage and the current of resistors to achieve the precise attenuation, direct voltage summing, and thus it offers an accurate and wide range interpolation than other interpolation techniques. The DAC employs only one amplifier to achieve the accurate voltage output with a wide output voltage swing with buffered output. Last, this architecture can be easily scaled for higher resolution (10-bit +) due to its linear and accurate interpolation with a monotonic response.
For additional technical information please check Prof. Sameer’s manuscript: “A 10-Bit Current Output DAC with Active Resistive Load Interpolation” Wang W. and Sonkusale S., IEEE Journal of Solid State Circuits, Vol. 68, No. 6, 2020
T002420 “D/A Converter with Resistive Interpolation”
- US Provisional Patent Application 63/069,809 filed 08/25/2020 (converted)
- PCT Patent Application PCT/US2021/07440 filed 08/25/2021