DESIGN AND IMPLEMENTATION OF A DUAL-CONTROL ACTIVE DEVICE USING YBCO GRAIN-BOUNDARY JUNCTIONS

We propose a dual-control active device based on overdamped long junct ions. In analogy to the semiconductor dual-gate field effect transisto r which can be considered a cascode (output terminals in series) of tw o single-gate FETs, the dual-control device consists of two single dev ices in parallel at the outputs. The transresistance of one device is shown to be a linear function of the second control current over a siz able range. This unique feature makes the dual-control device highly d esirable for applications such as gain control and mixing. Active devi ces have been fabricated using arrays of YBCO bicrystal grain-boundary junctions. Tight coupling of the control fields to the array was achi eved by injecting the control current into an ''ear'' structure at one end of the array. The large-signal current gain, however, is less tha n 1 due the asymmetric bias and end injection. Improved current gain w ith tight coupling to the entire array is necessary for a practical du al-control device.