title: Digital-to-analog converter using a superconducting quantum interference device.
abstract: We developed a digital-to-analog converter (DAC) having a current output and incorporating a superconducting quantum interference device (SQUID). The linearity of the device is based on the periodic dependence of the SQUID response on the magnetic flux coupling to the SQUID ring. The period is a flux quantum (Φ(o) = h/2e, where h is Planck's constant and e is the elementary charge). Because of the device's quantum accuracy, the output is essentially linear. The SQUID DAC was constructed using a commercially available rf-SQUID, the periodicity of which has been experimentally verified below 3420 Φ(o). An adjustable number of current amplitudes are dependent on maximum output (I(max)). The output current is adjustable to ~100 000 different values when I(max) ~1 mA and ~1,000,000 when I(max) ~0.1 mA. The short-term fluctuation of ~0.15 ppm was attributable to flux resolution of the SQUID. As a demonstration, measurements showing the voltage linearity of a digital multimeter were performed.
authors.affiliation: Metrology Institute of Japan, National Institute of Advanced Industrial Science and Technology, AIST Central-3, 1-1, Umezono, Tsukuba, Ibaraki 305-8563, Japan. m.nakanishi@aist.go.jp
authors.forename: Masakazu
authors.initials: M
authors.lastname: Nakanishi