[C-8] Superconducting Electronics

10:45 AM - 11:00 AM JST(1:45 AM - 2:00 AM UTC)Candidate for Academic Incentive Award

[C-8-05] Expanding the Tunable Range of Variable Characteristics Current Comparator composed of Superconducting Quantum Interference Device

◎Haruka Asano¹, Nobuyuki Yoshikawa¹, Yuki Yamanashi¹ (1. Yokohama National Univ.)

Keywords:

Single Flux Quantum,Josephson Junction,Superconducting Quantum Interference Device

The Current Comparator (CC) is a key component of Single Flux Quantum (SFQ) circuits, including Superconductive Random Number Generators (SRNGs). However, fabrication variations in the critical currents of Josephson Junctions (JJs) cause deviations in the grayzone characteristics of the CC. In this study, a variable-characteristic CC using a dc Superconducting Quantum Interference Device (SQUID) was evaluated. Measurement results from five conventional SRNG chips showed fabrication-induced variations of approximately 50 μA in the threshold current and 4 μA in the grayzone width. Although the proposed circuit can sufficiently compensate for the threshold variation, the tunable range of the grayzone width is limited. Simulations demonstrated that doubling the critical currents of the JJs in the SQUID expands the tunable range of the grayzone width, while increasing the sensitivity to the applied magnetic flux. These results provide a guideline for optimizing SQUID parameters to improve post-fabrication tunability.