dc SQUID's I–V Characteristics and Its Bias Modes

Summary

The physics of a DC Superconducting QUantum Interference Device (SQUID) involves two phenomena: flux quantization and Josephson tunneling. This chapter describes how to measure and understand a SQUID's I–V characteristics. It also describes how to realize an ideal current source for biasing a SQUID and how to set up a practical voltage source to operate a SQUID in voltage bias mode. To study a DC SQUID's features, the first step is to obtain its I–V characteristics. In contrast to the I–V characteristics of the resistor or the diode, those of the SQUID are modulated by the applied flux but are limited within two flux states of integer and half‐integer. An ideal current source is characterized by an internal resistance approaching infinity, compared to the SQUID's dynamic resistance. There are only two realized concepts for the SQUID operation in voltage bias mode.