Constant-voltage steps at 0.1 Volt from a series array of high-Tc Josephson junctions

By employing an array of 620 high-T
_c
Josephson junctions, we have achieved a maximum quantum output voltage with approximate value of 0.1 V at a temperature of 79.2 K and a frequency of 77.465 GHz. We also demonstrate that steps on the current-voltage characteristic of an array of bicrystal junctions at voltages of 70 mV were flat over the current range of 150 muA with a relative uncertainty of 0.04 ppm.