Low-voltage low-power high dB-Linear CMOS exponential function generator using highly-linear V-I converter

A CMOS voltage-to-current converter with exponential characteristic is presented in this paper. The concept of Taylor series expansion is used for realizing the exponential characteristic. The proposed exponential V-I converter is composed of a current-to-current squarer and a linear V-I converter with the use of linearization technique. Based on a 0.25 /spl mu/m CMOS process, simulations show a 23 dB of linear-output current range and the linearity within 20 dB with error less than /spl plusmn/0.5dB is achieved. The total power consumption is below 0.2 mW with 1.25 V supply voltage. The proposed circuit can be used for the design of an extremely low-voltage low-power variable gain amplifier (VGA).