LINEARIZATION ANALYSIS OF THRESHOLD CHARACTERISTICS FOR SOME APPLICATIONS OF MUTUALLY COUPLED SQUIDS

The threshold characteristics of mutually coupled SQUIDs (Superconduct ing Quantum Interference Devices) have been analytically and numerical ly investigated. The mutually coupled SQUIDs investigated is composed of an rf-SQUID and a dc-SQUID. Here, the rf-SQUID is a flux quantum ge nerator and the dc-SQUID is a flux detector. The linearization method substituting sin-1x by (pi/2)x (-1 less-than-or-equal-to x less-than-o r-equal-to +1) is found valid when it is applied to the mutually coupl ed SQUIDs, because it is possible to obtain the superconducting region s analytically. By computer implementation of linearization method, we found this method is very effective and very quick compared to the or dinary methods. We report the internal flux of an rf-SQUID. the thresh old of a dc-SQUID, and that of mutually coupled SQUIDs obtained by Lag range multiplier formulation and linearization. The features of the th reshold characteristics of the mutually coupled SQUIDs with various pa rameters are also reported. The discontinuous behavior of threshold of the mutually coupled SQUIDs are attractive for digital applications. We suggest three applications of the mutually coupled SQUIDs, that is, a logic gate for high-T(c) superconductors (HTSs), a neuron device, a nd an A/D converter.