On Measures of Logic Performance: Logic Quantum, Factor, and Figure of Merit

A basic logic operation is considered of transferring a logic decision from one point to another point. A certain energy level, W
L
, corresponding to decision threshold and a time delay, T
L
, are encountered in the transfer process. The product, W
L
T
L
, is a logic quantum, H
L
. if the logic transfer takes place through an intermediate device, a logic factor, F
L
, can be introduced to describe the reduction in logic quanta that the device can produce under optimum conditions. Optimization is carried out, as for instance with ideal transformers, to “match” the logic source to the device and the device to the logic detector. The condition F
L
= 1 marks a boundary between a useful and a useless device, and a logic figure of merit, T
FM
, in units of time corresponds to the fastest source-detector combination such that F
L
= 1. Logic performance is considered in some detail for a particular linear model of a device. Nonlinear devices and relay devices are considered in less detail, although some numerical calculations are given for a current-switch, two-transistor computer device. The logic figure of merit represents a unique measure of high-speed logic performance and is therefore valuable in comparing devices including associated circuitry on a common basis.