AN ALL THIN-FILM RESISTIVE DC SQUID - A CURRENT-CONTROLLED OSCILLATOR

An all thin-film resistive SQUID With two Josephson tunnel junctions has been designed, fabricated and studied. As well as the two junctions, this device consists of a low ohmic (1.9 x 10(-6) OMEGA) resistive part connected by superconducting leads to both junctions in a loop with very low (approximately 10(-11) H) inductance. A direct current flowing through the resistive part fixes the voltage difference between the two Josephson junctions that are additionally fed by a bias current. The voltage difference is converted into a signal frequency that can be picked up from the SQUID with a conversion factor of (phi0)-1 = 483.6 MHz muV-1, defined only by the electron charge and Planck's constant. An output signal level (peak-to-peak) of about 50 muV has been obtained. The low frequency range (below 100 kHz) of the output signal frequency has been investigated. The possibilities of considerably extending this frequency range are also discussed.