THRESHOLD CHARACTERISTICS OF MUTUALLY COUPLED SQUIDS.

The threshold characteristics of two nested SQUIDs has been investigated. Due to the flux quantization requirement of the larger SQUID loop, the threshold current of the smaller SQUID loop exhibits a large abrupt jump as the externally applied flux increases to a level beyond PHI //0/2 in the larger SQUID loop, when the larger SQUID is not biased. The threshold curve of the smaller SQUID changes dramatically when the larger SQUID is biased near its maximum critical current. The potential digital application of the coupled SQUID system is discussed.