טכניון מכון טכנולוגי לישראל
הטכניון מכון טכנולוגי לישראל - בית הספר ללימודי מוסמכים  
M.Sc Thesis
M.Sc StudentCohen Yaron
SubjectLow Power D/A Converter Design Considerations
DepartmentDepartment of Electrical Engineering
Supervisors Professor Emeritus Avinoam Kolodny
Professor Ran Ginosar
Dr. Aharon Unikovski
Full Thesis textFull thesis text - English Version


Abstract

Analog-to-digital converters (ADCs) and digital-to-analog converters (DACs) are crucial building blocks in today’s systems. Though most of the signal processing is done in the digital domain, the information should be transferred by analog signals. Current steering DAC is concerned as a solution for high speed video applications. In this architecture, once a high impedance current source is designed, conversion is linear due to a fast time constant which is dominated by an internal capacitance and characteristics impedance. In addition, the current steering DAC can be easily integrated with a standard CMOS process with relatively small area.

For low power applications such as portable systems, using a current steering DAC might not be the best solution as it consumes a considerable amount of power. In a single ended operation the power efficiency of the DAC is low. In order to maintain a constant current flow, some of the current is steered to the ground node and not to the signal’s path. In case the DAC should drive a long transmission line, termination at the source is required in order to prevent reflections and reduce the signal’s distortion. The power dissipated on the source termination reduces the power efficiency of the system even more.

In this work a design of a digital to analog conversion system aimed for low power single ended applications is introduced. The system is constructed from a fully binary low current steering DAC with a differential low power trans-impedance amplifier and an output stage to drive the load. A novel switch capacitor architecture is used to convert the differential signal at the output of the trans-impedance amplifier to a single ended Signal. An output buffer with impedance matching technique is used to drive the output signal to a transmission line.