Building multi-input RTD circuits under reliability constraints

Threshold functions can be implemented in nanotechnol-ogy using the MOBILE architecture based on resonant tun-neling diodes (RTDs). The operational reliability of the ar-chitecture is greatly dependent upon the number of RTDs used, due to the variance of the accumulated peak currents. This constrains the number of inputs to the threshold circuit. The number of inputs is also a measure of the area and in-terconnect complexity. This paper shows that a threshold function with n inputs can be implemented as a network of smaller threshold functions. Our implementation uses linear chains of identical threshold functions and is there-fore easier to fabricate and can be easily pipelined for high throughput. The total input complexity of all the functions involved in our implementation is O(nR2), where R is the difference between the sum of all the positive weights and the threshold. This compares very favorably with the tradi-tional decompositions of threshold functions which have a total input complexity of O(2n).