Dynamic charge restoration of floating gate subthreshold MOS translinear circuits

Abstract

We extend a class of analog CMOS circuits that can be used to perform many analog computational tasks. The circuits utilize MOSFET's in their subthreshold region as well as capacitors and switches to produce the computations. We show a few basic current-mode building blocks that perform squaring, square root, and multiplication/division which should be sufficient to gain an understanding of how to implement other power law circuits. We then combine the circuit building blocks into a more complicated circuit that normalizes a current by the square root of the sum of the squares (vector sum) of the currents. Each of these circuits have switches at the inputs of their floating gates which are used to dynamically set and restore the charges at the floating gates to proceed with the computation.