High-accuracy function synthesizer circuit with applications in signal processing

An original low-voltage current-mode high-accuracy function synthesizer circuit will be presented, allowing to implement a multitude of continuous mathematical functions. The dynamic range is strongly extended as a result of the superior-order approximation of the implemented functions. The current-mode operation and the independence of the circuit performances on technological parameters are responsible for an additional improvement of structure accuracy. The advantages of reduced design costs per function represent an immediate consequence of the multiple functions realized by the proposed structure. The approximation error of the original function synthesizer circuit is 0.3% for an extended range of the input signal. The function synthesizer is designed for implementing in 0.18 μm CMOS technology and it is supplied at 1 V. An original application of the proposed function synthesizer circuit is represented by a new fourth-order approximation exponential function generator, having a dynamic range of approximately 33 dB, for an error smaller than 1 dB.