A Calibration-Free, 16-Channel, 50-MS/s, 14-Bit, Pipelined-SAR ADC with Reference/Op-Amp Sharing and Optimized Stage Resolution Distribution
Round 1
Reviewer 1 Report
Thanks for your paper which reflects a huge volume of work (design&test)
I have a few questions:
1)The cross-talk testing results is missing; this is crucial for any multichannel applications like the one you target.
2) Figure 14.b : how can you measure the SNDR up till 80MHz, with a sampling rate limited at 50 MSps?
3) What could be the reason limiting your SNDR value?
4) The very title of the publication talk about “calibration free”. But the design uses some redundancy (16 bits), and usually this redundancy allow some calibrations before one get the final 14 bits. If you do not calibrate, it would be important to explain how you go from 16 bits to 14 bits. This is done in the “ADDer” stage, but a little explanation will be useful.
5) In Fig. 15, please check “comparator” expression.
6) You explain that a feedback classical amplification is used (paragraphe 1.2) but one can not find in the document how much is the gain of this residue amplification? How this gain (feedback) impacts the scaling in your comparator design in the successive stages.
7) Can you at least provide the overview of the comparator’s requirements in the more critical first stage? Maybe this can explain your SNDR value in combination with the KT/C issues in the first stage.
Author Response
Please see the attachment.
Author Response File: 
Author Response.pdf
Reviewer 2 Report
The manuscript entitled "A Calibration-Free 16-Channel 50-MS/s 14-bit Pipelined-SAR
ADC with Reference/Op-amp Sharing and Optimized Stage
Resolution Distribution" by Wu et al. introduced a reference sharing platform for the ultrasound imaging system with improved performance and less power consumption. This manuscript indeed provides a regime to enhance the performance of the ultrasound imaging system. However, the manuscript's overall structure makes the study elusive. For example, although the authors claimed the summary of each section at the end of the introduction, it is hard to grasp the novelty of this proposed platform compared with other studies as the related discussion is not focused. In section 2, followed authors' last paragraph in 1.1 Introduction, it should be result section? But some paragraphs are written like the introduction. In section 3, is that arranged to be Methods? If so, please make it more clear. Collectively, I would like to recommend the publication of this paper if the authors can make the structure more precise. In other words, please point out which section is Method, Materials, Results to make this manuscript easier to be followed.
1. what is the full name of FPGA in Introduction 1.1
2. Please keep the font the same in each figure
3. Please elaborate on each figure legend instead of only providing one brief sentence as the summary.
4. In 3.2.1, there is no clear description of equation 5. Please denote it in this section. And also, please check equation (6) -- whether it is from the combination of (3) and (4) or equation (3) or (5)?
5. Please keep the denotation of "Figure" or "Fig." in the main manuscript the same
Author Response
Please see the attachment.
Author Response File: Author Response.pdf
Round 2
Reviewer 1 Report
Thanks. You addressed positively all my questions.
Reviewer 2 Report
Thank you very much for addressing the comments and revising the manuscript.
I would like to recommend its publication after authors' proofreading to correct the typos or the formats. For example: please add the quote "()" to 6 for equation 6 in the main manuscript.
