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

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 PrBaCuCaO-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 I_cR_n-product of a reference junction