Single-Branch Wide-Swing-Cascode Subthreshold GaN Monolithic Voltage Reference

Round 1

Reviewer 1 Report

1) The references [22-23] are missing from the introduction, going from [21] directly to [24]. Please solve.
2) Figure 1 looks unfinished at the bottom, but figure 2 is actually cut down and a good piece of it is missing at the bottom and right. Please solve.
3) The bottom and right of figure 3 are not visible. Check and solve.
4) The bottom and right of figure 4 are not visible. Check and solve.
5) Figures 5, 6, 7, and 8 are completely blurred and need to be completely redone to become visible.
6) Figure 9, although visible needs a higher resolution to become clearer.
7) Figure 4 in section 3 requires further discussion.
8) Before Table 1, more extensive discussions with more explanations are needed. The same is required for Figures 5, 6, and 7.
9) Discuss Figures 8 and 9 and Table 2 in more detail.
10) Before the "Conclusions" section inserts an additional "Discussion" section that presents in detail all the advantages of the paper compared to other papers in the known literature and highlights everything that brings new and important work to this paper. The advantages of the new methodology as well as its limitations will be highlighted.
11) Also here could be described and briefly presented some possible applications.
12) The "Conclusions" section needs to be developed or even rewritten.
13) Enter an additional section at the end with possible "Future Research".

 

 

 

Author Response

Rev.1

Comments and Suggestions for Authors

 

1) The references [22-23] are missing from the introduction, going from [21] directly to [24]. Please solve.

REPLY.  We solved the issue and also eliminated [22] as requested by the second reviewer.
2) Figure 1 looks unfinished at the bottom, but figure 2 is actually cut down and a good piece of it is missing at the bottom and right. Please solve.

REPLY. Our apologies. We don’t understand the reason why the Figures, that appear correctly in the word file, are badly converted in pdf. We will double check in the revised submission.

3) The bottom and right of figure 3 are not visible. Check and solve.

REPLY. See reply to comment #2.
4) The bottom and right of figure 4 are not visible. Check and solve.

REPLY. See reply to comment #2.
5) Figures 5, 6, 7, and 8 are completely blurred and need to be completely redone to become visible.
REPLY. See reply to comment #2.

6) Figure 9, although visible needs a higher resolution to become clearer.
REPLY. We increased the resolution of the figure.

7) Figure 4 in section 3 requires further discussion.
REPLY. We completely rewrote section 3 and now explain better the circuit operation in Sec. 3.1.  

8) Before Table 1, more extensive discussions with more explanations are needed. The same is required for Figures 5, 6, and 7.
REPLY. Before Table 1 (now Table 2, in the revised manuscript), we added paragraph 3.2 Analysis and design strategy, in order to clarify the deign steps and the component values chosen in Table 1.

9) Discuss Figures 8 and 9 and Table 2 in more detail.
REPLY. As requested we added further discussion for figures and tables.

10) Before the "Conclusions" section inserts an additional "Discussion" section that presents in detail all the advantages of the paper compared to other papers in the known literature and highlights everything that brings new and important work to this paper. The advantages of the new methodology as well as its limitations will be highlighted.
REPLY. We do not add a specific Discussion section, as the discussion is spread in the new material added in Sec. 3 and 4.

11) Also here could be described and briefly presented some possible applications.
REPLY. The applications of a voltage reference are in any IC in which we need a stable reference voltage, we do not think this has to be further stressed.

12) The "Conclusions" section needs to be developed or even rewritten.
REPLY. We rewrote and extended the Conclusions as requested.

13) Enter an additional section at the end with possible "Future Research".

REPLY. We added a final paragraph in the Conclusions anticipating the future research.

Reviewer 2 Report

The manuscript by Bimbi et al. reports on the design and simulation of voltage reference generator for GaN devices. The design builds upon previous low-power monolithic designs and predicts an improved line regulation and smaller occupation area.

The topic of GaN-based technologies is relevant for a journal such as Electronics and the manuscript contributes to the design of more efficient devices for these technologies. The general context and previous related monolithic voltage reference generators are correctly motivated, and I believe that the analysis is soundly conducted, although I must admit that I had trouble understanding parts of it. I think that the authors should make an effort at better explaining their analysis (see below), as well as improve the quality of their figures, before the manuscript can deemed to be in a publishable form.

Below is a list of points (major or minor) to address

-There seems to be a margin problem with Figs. 1-4, which are "cut", at least in the version I received. Some quantities are not introduced or their notation is not consistent (e.g. V_REF is sometimes V_F).

-l. 173: the authors should expand on their choice of a resistance ratio of 1.8 (at least give the corresponding "occupation area" and "temperature coefficient" in the "ideal" case).

-l. 188-189: what do the authors mean by "Below 3.9 V the circuit does not work properly"?

-l. 200: the authors should properly introduce the "SS, TT, FF cases" of the corner analysis.

 

Author Response

The manuscript by Bimbi et al. reports on the design and simulation of voltage reference generator for GaN devices. The design builds upon previous low-power monolithic designs and predicts an improved line regulation and smaller occupation area.

The topic of GaN-based technologies is relevant for a journal such as Electronics and the manuscript contributes to the design of more efficient devices for these technologies. The general context and previous related monolithic voltage reference generators are correctly motivated, and I believe that the analysis is soundly conducted, although I must admit that I had trouble understanding parts of it. I think that the authors should make an effort at better explaining their analysis (see below), as well as improve the quality of their figures, before the manuscript can deemed to be in a publishable form.

Below is a list of points (major or minor) to address

-There seems to be a margin problem with Figs. 1-4, which are "cut", at least in the version I received. Some quantities are not introduced or their notation is not consistent (e.g. V_REF is sometimes V_F).

REPLY. We apologize for the poor quality of the pdf file. The word versions was correct, but in the conversion to pdf something wrong occurred. We will pay attention and double check during the submission of the revised version of the manuscript.

-l. 173: the authors should expand on their choice of a resistance ratio of 1.8 (at least give the corresponding "occupation area" and "temperature coefficient" in the "ideal" case).

REPLY. The revised version of the manuscript discusses the design choices in detail by adding a further section 3.2 Analysis and design strategy.

-l. 188-189: what do the authors mean by "Below 3.9 V the circuit does not work properly"?

REPLY. From Figs. 6 and 7 we see that below 3.9 V the circuit does not keep constant the reference voltage, and therefore fails in its main purpose.

-l. 200: the authors should properly introduce the "SS, TT, FF cases" of the corner analysis.

REPLY. We explained the meaning of the corner cases in Sec. 3.2.

Reviewer 3 Report

The manuscript describes Single-branch Wide-swing-cascode GaN Monolithic Voltage Reference. Here are some concerns from my side. Despite the topic presented being attractive, the manuscript is not yet well prepared and not ready for publication. Here are some concerns from my side.

1. In conclusion, the authors claimed, “A novel voltage reference generator fully implementable in a smart power GaN.” This statement is misleading since the authors only perform a simulation study. Full implementation should combine both experimental measurement and simulation results.
2. Some parts in Figures 1, 2, 3, and 4 are cropped. Please make sure that the correct figures are presented.
3. The format applied in this manuscript is not standard for a research article. For instance, in Section 2, paragraphs are strongly suggested rather than a list or numbering.
4. Please compare Table 1 from the resulting simulation with the schemes in Figure 3 and Figure 4.
5. Please add more updated references for the introduction part in the first paragraph. If possible, please replace outdated references in the second paragraph. More importantly, the novelty of the study should be well sounded.
6. Please use more references from reputable journals and reduce the use of references from (non-published) conference proceedings, especially since I found one from “submitted/accepted” conference participation.
7. Figures 1-3 are from references 26 and 27, make sure authors get a copyright statement from the publisher if the referred publication is not open access.
8. This proposed study predominantly only compares these results to their group´s previous studies (Table 2). More published works from other groups must be explored and compared to make a solid comparison.
9. Some recently published technology related to this work can be used as references. Please check them out. (a).Electronics 2022, 11(1), 42; https://doi.org/10.3390/electronics11010042. Circuit Techniques in GaN Technology for High-Temperature Environments, (b). IEEE Electron Device Letters ( Volume: 43, Issue: 3, March 2022). 10.1109/LED.2022.3146263. A Monolithically Integrated 2-Transistor Voltage Reference With a Wide Temperature Range Based on AlGaN/GaN Technology

Author Response

The manuscript describes Single-branch Wide-swing-cascode GaN Monolithic Voltage Reference. Here are some concerns from my side. Despite the topic presented being attractive, the manuscript is not yet well prepared and not ready for publication. Here are some concerns from my side.

1. In conclusion, the authors claimed, “A novel voltage reference generator fully implementable in a smart power GaN.” This statement is misleading since the authors only perform a simulation study. Full implementation should combine both experimental measurement and simulation results.

REPLY. “Fully implementable” in our intention means “that can be implemented in a full-GaN technology”. We changed the sentence accordingly to avoid confusion. “The aim of this paper was to present a novel topology of reference voltage generator amenable for GaN IC processes, together with its optimal design methodology.”

1. Some parts in Figures 1, 2, 3, and 4 are cropped. Please make sure that the correct figures are presented.

REPLY. Our apologies. We don’t understand why the Figures that appear correctly in the word file are badly converted in pdf. We will double check in the revised submission.

1. The format applied in this manuscript is not standard for a research article. For instance, in Section 2, paragraphs are strongly suggested rather than a list or numbering.

REPLY. We thank the reviewer for the suggestion that we implemented in the revised version.

1. Please compare Table 1 from the resulting simulation with the schemes in Figure 3 and Figure 4.

REPLY. We do not understand the comment. Table I (now Table 2) summarizes the component dimensions of circuit in Fig. 4 (now Fig. 5, the proposed one). Perhaps the reviewer asks a comparison with the dimensions of the other previously proposed circuits. Unfortunately, such information is not included in the original referenced papers that do not report transistors and resistors dimensions.

1. Please add more updated references for the introduction part in the first paragraph. If possible, please replace outdated references in the second paragraph. More importantly, the novelty of the study should be well sounded.

REPLY. We thank the reviewer for this suggestion that was received. We added other two solutions, and described better the novelties of the design that are mainly in the subthreshold operation and the new design methodology.

1. Please use more references from reputable journals and reduce the use of references from (non-published) conference proceedings, especially since I found one from “submitted/accepted” conference participation.

REPLY. We added the reference form a respected conference (IEEE ISCAS), just to show our parallel work on other GaN building blocks, an amplifier that can be used to realize an LDO following the reference generator. There are 32 references on top journals and 3 conference papers that are strictly related to the topic.

1. Figures 1-3 are from references 26 and 27, make sure authors get a copyright statement from the publisher if the referred publication is not open access.

REPLY. The figures were completely redrawn. In our more than 30-year experience, there is no problem of copyright when properly citing prior art and showing circuit schematics of public domain.

1. This proposed study predominantly only compares these results to their group´s previous studies (Table 2). More published works from other groups must be explored and compared to make a solid comparison.

REPLY. We totally disagree with this comment. We compare our original work to previous studies of other groups. In the revised manuscript we are adding other solutions from the literature, as also suggested by the reviewer in the subsequent point 9.

1. Some recently published technology related to this work can be used as references. Please check them out. (a).Electronics 2022, 11(1), 42; https://doi.org/10.3390/electronics11010042. Circuit Techniques in GaN Technology for High-Temperature Environments, (b). IEEE Electron Device Letters ( Volume: 43, Issue: 3, March 2022). 10.1109/LED.2022.3146263. A Monolithically Integrated 2-Transistor Voltage Reference With a Wide Temperature Range Based on AlGaN/GaN Technology

REPLY. We thank the anonymous reviewer for having suggested additional works that were not previously known by us.

Reviewer 4 Report

1) Please try to keep the same style throughout the text to denote designations. For instance in some parts the: VREF is used in other parts: Vref.

2) In Fig. 2 the Wilson current mirror is not properly visible. Please also improve the quality of Fig. 4 and Fig. 7.

3) It would be desirable if the authors provide more technical description of the developed model.

4) Please improve in conclusion part make it more clear for the reader. 

Author Response

1) Please try to keep the same style throughout the text to denote designations. For instance in some parts the: VREF is used in other parts: Vref.

REPLY. We corrected the issue.

2) In Fig. 2 the Wilson current mirror is not properly visible. Please also improve the quality of Fig. 4 and Fig. 7.

REPLY. Our apologies. We don’t understand why the Figures, that appear correctly in the word file, are badly converted in pdf. We will double check in the revised submission.

3) It would be desirable if the authors provide more technical description of the developed model.

REPLY. We added a better description of the circuit in the completely rewritten section 3.1. Moreover, we proposed in the completely new sec. 3.2. a design methodology and model equations. We are particularly indebted with the reviewer for the suggestion.

4) Please improve in conclusion part make it more clear for the reader. 

REPLY. We rewrote completely the Conclusions. We hope now meets the reviewer expectations.

Round 2

Reviewer 1 Report

1) There are two different equations numbered with 5. Please change.
2) Two different figures numbered 9 appear. Please change.

Reviewer 3 Report

The authors have properly addressed all the questions.