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					DIGITALLY ASSISTED ANALOG
        CIRCUITS
          PRESENTATION
                 By
        Sohaib Saadat Afridi
              MS (EE)
               SEECS
               NUST



                               1
                    Agenda
•   Introduction
•   Motivation
•   Goals
•   Recent research trends
•   Key Research Labs
•   Published Research
•   Summary
•   Conclusion

                             2
                     Introduction
• Digitally Assisted Analog Circuits.
• This term was used first as a research title in 2004 [1].

• Analog functionalities needed in modern mixed-signal
  integrated systems [3].
   – Signal Conversion (A/D & D/A)
   – Filtering
   – Signal Amplification
• The goal is to implement these functions on CMOS in
  today's mixed-signal systems.
• With better efficiency (improve speed & power dissipation)


                                                               3
                       Motivation
• Progress in digital circuits has outpaced performance
  growth in analog circuits
   –   High speed
   –   Higher device density
   –   Low power consumption
   –   scalable, synthesizable, and self-testable
   –   Signal processing predominantly done in digital domain

• Problems in analog circuits on the same level
   – Non-linearity
   – Device specific noise
   – Limitations in accuracy and speed.

                                                                4
                      Goals
 Reduce power consumption/voltage supply[2 & 3].
 Reduce mismatch between different processes[2].
 Higher speeds.[2]
 Improve capacitance linearity [3]
 Ability to design with reduced element set [3]




                                                    5
                                   Goals [cntd]
                       ADC            Signal Conditioning
    Digital                                                 Analog media &
  Processing                                                  transducers
                       DAC            Signal Conditioning




                       Low power           Minimal
            Post-
          Processing   consuming
Digital                   ADC         Signal Conditioning   Analog media &
Process                                                       transducers
             Pre-      Low Power           Minimal
          Processing   consuming
                          DAC         Signal Conditioning




                                                                             6
           Recent research trends
• The areas where aforementioned goals are required
   –   Data Converters
   –   Power Amplifiers
   –   Direct conversion receivers
   –   Delta Sigma Modulators

• There are many ways to take advantage of digital
  assistance:
   – Calibration
   – Digital compensation for analog impairments
   – Feedback and feed-forward networks

                                                      7
                       Example
A 12-bit 75MS/s Pipelined ADC using Open-loop Residue Amplification




                                                                      8
                Example[cntd]
A 12-bit 75MS/s Pipelined ADC using Open-loop Residue Amplification




             Conventional Approach

                                                                      9
                    Example(2)
A 12-bit 75MS/s Pipelined ADC using Open-loop Residue Amplification




                 Proposed Open Loop Circuit


                                                                      10
             Key Research Labs
• Dr. Boris Murmann of the Electrical Engineering
  Department at Stanford University, USA.
   – http://www.stanford.edu/group/murmann_group/
• Dr . Joel L. Dawson at Dawson Research Group,
  MIT,USA.
   – http://www-
     mtl.mit.edu/~jldawson/research_group/people.html
• Dr. Christian Vogel at Graz University of
  Technology, Austria.
   – http://www2.spsc.tugraz.at/people/cvogel/index.html

                                                        11
               Published Research
• "A 12-bit 75-MS/s pipelined ADC using open-loop residue
  amplification. "by Murmann, B. and B. E. Boser . IEEE Journal
  of Solid-State Circuits,2005. -Cited by 262
• “Digitally assisted analog circuits” by B Murmann; - Micro, IEEE,
  2006. Cited by 39.
• “A 5-GHz 20-dBm power amplifier with digitally assisted AM-
  PM correction in a 90-nm CMOS process” by Palaskas, Y.
  Taylor;- IEEE Journal of Solid-State Circuits Aug. 2006 - Cited
  by 19.
• “Efficiency improvement techniques at low power levels for
  linear CDMA and WCDMA power amplifiers” by T Fowler, K
  Burger, NS Cheng ,Radio Frequency Integrated Circuits (RFIC)
  Symposium, 2002 -Cited by 61                                    12
                 Conclusion
• Digital circuits are most cost and area effective
  while offering higher yield.
• Digital assistance will help improve analog
  circuits to achieve low power consumption,
  high speed and linearity.
• It can be achieved through complete
  transformation of analog circuits into digital
  circuits or by correction of analog domain
  issues in the digital domain.

                                                  13
                 References
• [1] Murmann, B. and B. Boser (2004). "Digitally
  Assisted Analog Integrated Circuits." Queue 2(1):
  64-71.
• [2] Murmann, B. (2006). "Digitally assisted analog
  circuits." Micro, IEEE 26(2): 38-47.
• [3] Leme, C. A. and J. E. Franca (1997). Analog-
  digital design in submicrometric digital CMOS
  technologies. Circuits and Systems, 1997. ISCAS
  '97., Proceedings of 1997 IEEE International
  Symposium on.
                                                   14

				
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