A novel CMOS exponential approximation circuit

A novel exponential circuit with a high output and input range is proposed. This circuit is based on a new exponential approximation function which can be implemented using new current mode circuits. This circuit consists of a current generator section and a current divider section. The current generating section produces currents that are exponentially dependent on input signals and the current dividing section produces a ration of exponential current. The HSPICE simulation results shows that this circuit is capable of having a nearly 60 dB output dynamic range with the linearity error less than plusmn 0.5 dB over a maximum input range with a 0.18 um CMOS technology.