A new implementation for the logarithmic/exponential function generator

This paper presents two new approximations for the logarithmic and exponential functions. These approximations require only a square rooter function, a scalar function and a constant. Thus, the realization of these functions in current-mode is simple, straightforward and uses less number of transistors. Simulation results obtained using the Tanner simulation software from Tanner EDA in 0.35μm standard CMOS technology show that the logarithmic and exponential functions can be obtained with good accuracy over a wide range of the input variable.