Split Capacitive Boosting Technique for High-Slew-Rate Single-Ended Amplifiers: Design and Optimization

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

1- Please clarify whether the authors are the first to explore single-ended slew rate enhancement. If similar approaches were previously reported, kindly provide proper citations or a discussion for context.

2- It is recommended to include a detailed discussion of the limitations of previously reported works, rather than simply claiming that single-ended slew rate enhancement has not been explored. This will provide a stronger foundation for the novelty of this work.

3- Please provide proper references for equations 3 and 4, as they appear to be derived from prior work. If these equations are original contributions, kindly state this explicitly.

4- Kindly clarify whether the analysis presented in Sections 2.2 and 2.3 is entirely original. If portions of the analysis are based on prior work, please provide appropriate references for the equations in these sections.

5- The manuscript claims that one of its novelties is "linking performance degradation to common-mode dynamics" (last paragraph of the introduction). However, the Gm-control technique discussed in Section 2.4 is cited from references 10 and 41. Kindly clarify how the manuscript's contribution builds upon or differs from the cited references. Furthermore, include a proper citation in the caption of Figure 5.

6- Kindly elaborate on the SCB technique’s impact on noise performance, linearity, or distortion, which are critical for analog circuits.

7- Kindly provide a detailed explanation of how the transistor sizing in Tables 1 and 2 was determined. It is highly recommended to include a theoretical analysis with defined performance metrics that justify these sizing choices. Without this information, the data in the tables lacks clarity and context.

8- Please include detailed information about the utilized PDK (process design kit) for the simulations in Section 2.5. This information is essential for reproducibility and validation.

9- Kindly elaborate on how the parameter values in lines 238-239 were chosen. It is recommended to include the design methodology or constraints that guided the selection of these values.

10- Kindly include the input voltage waveform in Figure 8 for better visualization and understanding of the low-to-high transitions.

11- The comparison table should be moved to the Results or Discussion section. The Conclusion section should focus on summarizing the main findings of the manuscript without referencing other papers.

12- Kindly elaborate on how the presented results might change after post-layout simulations. Discuss any anticipated differences in performance metrics such as settling time, slew rate, and power consumption.

Comments on the Quality of English Language

There are a few English writing mistakes in the manuscript. For instance, in line 42, the word “choiche” should be corrected to “choice.” A thorough review of the manuscript is recommended to identify and correct all grammatical and typographical errors.

Author Response

Please see the attachment.

Author Response File: Author Response.pdf

Reviewer 2 Report

Comments and Suggestions for Authors

This work represents split capacitve boosting technique for high-slew-rate signle-ended amplifiers with design and optimization. The authors provide the qualitative analysis for high-slew-rate with the mathematical expressions. Here are my comments.

1. The manuscript contains several typographical and grammatical errors (ex, page1 line 32 deatcitvating, line 33 transitions, page 2 line 42 choiche, page 3 line 54 transcunductor ...) that should be carefully revised for clarity and correctness.

2. In Fig. 1(d) and (e), the current sources (Itail1) are overlapped with the differential amplifier symbols. It seems to be modifiy for clarifying the figure.

3. Spliting capacitve booster could help to get higher common mode gain at higher frequency, which leads to degradation of CMRR. Please show the CMRR simulation result and comment the CMRR effect on the slew rate. 

4. The analytical derivations are overall consistent and insightful. However, several equations (notably, Eq. (4), (5), (20), and (29)) rely on idealized assumptions. The detailed comments are shown as below.

1) Regarding Eq. 4

 The activation voltage VA under strong inversion region is derived using the EKV-based square-law approximation and assumes beta_ia=alpha * beta_i. Could the authors clarify the conditions under which this assumption holds, and wheter the modle remains accurate under moderate inversion operation or PVT variations? Additionally, for the circuit designer, please provide the method to extract the EKV model parameters.

2) Eq. 5

 The turn-on delay (ton) is modeled using gate capacitance and constant transconductance parameters. Given that these parameters can be dynamic during slewing, how sensitive is the model to variations in beta_m and I_m? Would be the authors consider including a brief justification or simulation-based validation of this approximation?

3) Eq. 20

  This expression models the slew-rate degradation due to capacitive boosting. However, it assumes that both differential pairs are active during the entire slewing phase. Since this work later discusses that one pair may turn off as Vo approaches the rail, should this limitation be explicitly stated with potential impact on design accurary?

4) Eq. 29

 The condition CBp > CL/K is critical for achieving optimal SCB performance. Could the authors elaborate on the physical or intuitive significance of this condition and whether it represents a hard boundary or a design guideline with some margin or flexibility?

5) Eq. 10 and 15

  The expressions for the initial output current rely on a square-law model and depend on achieving sufficient ΔVGp or ΔVGpn. Could the authors clarify the minimum effective value of ΔVG required for substantial boosting, and how this interacts with PVT variations or mismatch in real implementations?

5. Some figure labels have typo. (ex, in fig 6, fig 6(b) shows the input & output voltage at the high-to-low transient, not low-to-high.)

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Author Response

Please see the attachment.

Author Response File: Author Response.pdf

Reviewer 3 Report

Comments and Suggestions for Authors

This paper introduces a Split Capacitive Boosting (SCB) technique for enhancing the slew rate and settling performance of single-ended operational transconductance amplifiers (OTAs), particularly useful in applications such as LCD/OLED drivers and capacitive-load interfaces. Though the work seems interesting, I have some suggestions for the authors to improve the submitted work for publication.

1. The authors did a great job writing the abstract section. It is clear, concise, and effectively summarizes the key contributions of the work. However, the introduction does not fully adhere to the structure typically expected in a research article or outlined by MDPI guidelines. In general, the introduction should begin by clearly stating the problem the research aims to solve, followed by a discussion of existing work in the field and the limitations of those approaches. It should then explain how the current work addresses these gaps. Optionally, the introduction can conclude by briefly outlining the structure of the paper. Including these elements would improve the clarity and contextual grounding of the research for readers and highlight the novelty and significance of the proposed method. What authors have written in the introduction, authors can create a separate section with a heading as background.
2. I really like authors testing their design in all the process corners in Table 4. I am also impressed that the authors compared their proposed designs with other published papers. However, Table 4 should be described in the conclusion; instead, it must be described in the results section.
3. While the total number of references cited in the manuscript appears reasonable at first glance, a closer look reveals a significant imbalance in their distribution. Specifically, out of the 41 references, 36 are concentrated within the first paragraph of the Introduction section. This clustering reduces the effectiveness of the literature review and does not align with the expectations for a journal article. In a well-structured research paper, references should be distributed more evenly across the manuscript, particularly throughout the Introduction and Related Work sections, to build a coherent narrative, support technical claims, and clearly highlight the gaps your work is addressing. I recommend revisiting the citation strategy and redistributing the references more thoughtfully across relevant sections of the paper.

The rest of the paper is acceptable.

Since the paper needs proper structuring to meet how a typical MDPI or other journals are structured, I recommend a major revision to the authors.

Author Response

Please see the attachment.

Author Response File: Author Response.pdf

Round 2

Reviewer 1 Report

Comments and Suggestions for Authors

All comments have been addressed.

Reviewer 3 Report

Comments and Suggestions for Authors

I appreciate the authors for thoughtfully incorporating my suggested changes. I am satisfied with all the revisions made.