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

We have successfully fabricated and tested a high temperature superconducti ng sigma-delta A/D converter. The quantizer is a balanced comparator that h as been characterized separately in two temperature regimes. The circuits h ave been fabricated with ramp edge junctions with a PrBaCuGaO-barrier on a buried ground plane, For the current to voltage conversion in the sigma-del ta converter we fabricated a 50 mOhm resistor with an in-situ gold layer. T he 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 freque ncy of 3.4 kHz and was at least 63 dB but most likely higher since the meas urement was limited by the noise in the amplifiers. As a first attempt towa rds 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 IcRn-product of a reference junction.