**7. Conclusions**

This paper described methods for developing the conceptual design of microelectronic circuits before performing schematic and layout simulations. The Excel methods developed here are useful for following guidelines and to make design decisions during iterative processes of designing where the number of specification requirements is larger than the degrees of freedom available to maneuver the design. The "thinking model" for paper and pencil calculations is described with the major roles and variants in the computation of electrical variables and sizes of the transistors that integrate analog microelectronic devices.

The Excel method may include straight single dimension, tabular, and two-dimensional methods that allow the design engineer to go step by step in the decision flow which navigates downwards in the Excel spreadsheet. Several examples of conceptual designs are shown with the corresponding spreadsheet diagram, circuit schematic, and layout design to perform simulation tests. The examples include passive components: resistors and capacitors, functional subcircuits such as primitive amplifiers, complete specialized amplifiers such as OTA devices, and term projects where students research specialized devices for biomedical instrumentation applications. The full-blown methodology includes the Excel method, schematic development, layout implementation, and simulation test, and it is used for conceptual design development in microelectronics courses at undergraduate and graduate levels. The undergraduate courses include industrial partner participation to develop instrumentation systems specified by industrial needs [43]; as a result, these educational collaborations with other entities have been applied in our academic educational practices and/or by applying our new educational model TEC21 at the undergraduate level [44–47]. As mentioned earlier, the main contributions of this research are in teaching CMOS microelectronics in which the method helps the instruction of the following points:


Finally, with the approach to teaching CMOS microelectronics and the use of readily available software such as Excel, it is possible to align teaching to reach the search for open innovation.

**Author Contributions:** G.D.-A., Conceptualization, methodology, simulation examples, validation, simulation validation, literature review, writing—original draft preparation, writing—review and editing, data processing, quantitative data collection, resources; J.M.R.-D., review conceptualization, methodology; O.I.G.P., Literature search, validation of the experimental methodology, review of data validation and simulations, analysis, writing, and editing. All authors have read and agreed to the published version of the manuscript.

**Funding:** This research received no external funding.

**Institutional Review Board Statement:** Not applicable.

**Informed Consent Statement:** Not applicable.

**Acknowledgments:** We wish to thank Steven Rubin and the crew that developed Electric-VLSI for the availability to have many professors, instructors and students working with this software in making conceptual designs of Microelectronic devices. Also, we want to acknowledge Analog Devices for the availability of its premier LTSpice software to professors, students and practicing engineers. Both software packages were very important in the validation of the conceptual designs developed by the Excel methods. Thanks must go to J. R. Baker and Philip Allen for their advice and workshops taken from 2005 until recently. Furthermore, we want to thank the Tecnológico de Monterrey, particularly the School of Engineering and Sciences (EIC), the Mechatronics and Electrical Engineering Department and the Computer Science Department for their faculty and student participation in the Microelectronic course TE-3034. In addition, a special thanks to the students who have participated in both courses, undergraduate and graduate level, since 2005 at Tecnológico de Monterrey, specially to Humberto González and Andrea Rodríguez who shared their term project design which was presented in this paper as a good example of using Excel methods to design microelectronic devices. Their participation enhanced the ideas and teaching strategies followed through the years while improving and refining the materials, simulation experiments and the fabless projects developed. Finally, the authors would like to acknowledge the Writing Lab, Institute for the Future of Education, Tecnologico de Monterrey, Mexico, for the financial and logistical support in the open access of this publication. This study belongs to the initiative R4C-IRG Reasoning for Complexity Interdisciplinary Research Group https://tec.mx/en/r4c-irg, accessed on 3 October 2021.

**Conflicts of Interest:** The authors declare no conflict of interest.
