Sigma-delta A/D converter in HTS ramp edge technology

Abstract

Abstract-we have successfully fabricated and tested a high temperature superconducting sigma-delta A/D converter. The quantizer is a balanced comparator that has been characterized separately in two temperature regimes. The circuits have been fabricated with ramp edge junctions with a PrBaCuGaO-barrier on a buried ground plane. For the current to voltage conversion in the sigma-delta converter we fabricated a 50 mOhm resistor with an in-situ gold layer. The sigma-delta converter has been tested at an internal clock of up to 174 GHz. The signal-to-noise ratio has been measured at a relatively low frequency of 3.4 kHz and was at least 63 dB but most likely higher since the measurement was limited by the noise in the amplifiers. As a first attempt towards the development of a decimation filter we have fabricated and tested a toggle flip-flop. The toggle flip-flop has been tested successfully at 40 K up to a frequency of 33 GHz, which corresponds to 70 % of the Isn-product of a reference junction.h d e x Terms-Balanced comparator, oversampling, AD converter, toggle flip-flop.

Weak link nanobridges as single flux quantum elements

“…The main body of work using SFQ circuits has either used complex multi-layer niobium technology-usually utilising niobium foundry fabrication [6], or high-T c fabrication techniques such as bicrystal junctions [7] and ramp edge junctions [8]. The weak links fabricated in this work aim to reduce the complexity of the fabrication by using only a single-step lithography process.…”

Superconductive Digital Magnetometers with Single-Flux-Quantum Electronics

“…The major goal was to design and validate experimentally a magnetic digital sensor for NDE with high dynamic range and a reasonable sensitivity better than 1 pT/ √ Hz that can operate in an unshielded environment [27]. In order to insure portability, the project included the development of a 2-stage cooler with a cooling power of 3 W at 70 K and 0.5 W at 30 K, associated with a digital SQUID gradiometer based on an already-proven high-Tc technology [28]. A constraint was to build a demonstrator from a digital circuit counting only a few tens of Josephson junctions to account for the moderate maturity of high-Tc superconducting digital devices.…”

Comparative study of rapid-single-flux-quantum devices based on low-, medium- and high-Tc technologies

“…In Europe, RSFQ fabrication processes range from conventional shunted Nb/AlO x /Nb Josephson junctions and NbN Josephson junctions to HTS Josephson junctions, and double barrier SINIS Josephson junctions. Different RSFQ devices have been demonstrated for all these processes [1][2][3][4][5], however not much effort has been put into performing a comparative study of device performances as well as improving the design efficiency of similar cells. A unified initiative has been taken within the European FLUXONICS [6] network to move towards an approach to join the libraries developed for different technological processes.…”