Circuit Analysis & Design Contest


 IEEE SSCS International Student Circuit Contest 

Submission Closed: Winners Announced!


The IEEE SSCS International Student Circuit Contest's objective is to engage students in thought-provoking circuit analysis and design problems. Submissions are solicited by both undergraduate and graduate students who are currently enrolled in a college or university. The IEEE Solid-State Circuits Society is pleased to announce the winners of it’s second annual student circuit contest:


                                                                     anoop photo SSCS ISCC                      shuoli 10x8 white

                                                                 Anoop Narayan Bhat, University of Twente          Shuo Li, University of Virginia.



This contest involved a feedback amplifier that at first glance seems to be unstable, but is perfectly stable. We asked for your intuitive explanation of this situation.


Considering the feedback amplifier shown below:


where the open loop amplifier A(s) is given by:


contest2019 2



If we investigate the Bode plot of the loop gain, we can confirm that at contest2019 3 (that is the angular frequency at which the phase of the loop gain reaches -180 degrees), the magnitude of the loop gain is much greater than 1 (in fact it is 36dB). We may naturally conclude that this feedback amplifier is unstable, simply because a signal at contest2019 3must grow out of bound as it goes around the loop. Yet, when we use the Nyquist plot, we find that this system is indeed stable.

We are reaching out to you, as an SSCS student member, to provide your intuitive reasoning for why this is the case. Please limit your intuitive explanations to a maximum of two pages.



Up to three contestants with best answers will receive US$2K each towards attending an SSCS-sponsored conference (ISSCC, CICC, ESSCIRC, VLSI Symp., ASSC). This award is paid either as a reimbursement following the attended conference or will be paid directly to the conference for registration and to the hotel for accommodations. All the submitters with the right answers will receive one year of free membership in the Solid-State Circuits Society, and their names will be highlighted in the Solid-State Circuits Magazine.