  The memristor, because of its controllability over a wide dynamic range of
resistance, has emerged as a promising device for data storage and analog
computation. A major challenge is the accurate measurement of memristance over
a wide dynamic range. In this paper, a novel read-out circuit with feedback
adjustment is proposed to measure and digitise input current in the range
between 20nA and 2mA. The magnitude of the input currents is estimated by a
5-stage logarithmic current-to-voltage amplifier which scales a linear
analog-to-digital converter. This way the least significant bit tracks the
absolute input magnitude. This circuit is applicable to reading single
memristor conductance, and is also preferable in analog computing where
read-out accuracy is particularly critical. The circuits have been realized in
Bipolar-CMOS-DMOS (BCD) Gen2 technology.
