Ultra low-voltage low-power exponential voltage-mode circuit with tunable output range

In this paper, an ultra low-voltage and low-power exponential voltage-mode circuit is developed using the "pseudo-exponential" approximation for realizing the exponential characteristics. The proposed circuit provides controllable output voltage range at very low-voltage applications (less than 1.2 V). In a 0.25 μm CMOS process, the simulations show more than 35 dB output voltage range and 27 dB range with the linearity error less than ±0.5 dB. The average power dissipation is less than 0.2 mW. The proposed circuit can be used for the design of an extremely low-voltage and low-power variable gain amplifier (VGA) and automatic gain control (AGC).