Current-Mode CMOS Galois Field Circuits

Use of current-mode CMOS circuits for implementation of multiple-valued logic (MVL) functions has been considered in a number of recent papers . In this paper, we present an application of these circuits in realization of Galoisfield operations. We also give a new algorithm for determination of polynomial representations for arbitrary functions over a class of Galoisjelds implementable with presently available MVL circuits. 1.0 Current-Mode MVL Functions Recent experience shows that current-mode circuits are attractive for implementation of MVL functions, particularly when the radix is greater than 3. Most of the circuits and synthesis techniques in the literature have been intended for the 4-valued environment [Z], [41, [5 ] . Current-mode circuits offer several advantages, but they also have some disadvantages. Perhaps the most important of these are the ease of summation of signals and the difficulty in distribution of signals caused by the fanout being equal to one. In practice, it is useful to augment the current-mode circuits with some intermediate voltage-mode circuits, which often results in more effective designs. Figure 1 gives the basic blocks used in our design. All of these blocks have been used before [2], [4], [5 ] . Here, we will only summarize their characteristics. Currents are summed by means of a simple wired connection. Current sources are realized as an N-type or a Ptype transistor with the gate connected to a reference voltage. The amount (value) of current is proportional to the ratio of W/L. Signal distribution can be performed using current m'rrors, which can be of either N-type or P-type. We will use both types. The current produced at the output is determined by the input current and the ratio between output and input W/L values. In addition to signal distribution, the current mirror will be used for multiplication with a constant and for sign reversal. FIGURE 1. Basic Current Mode Blocks Name