Low-voltage CMOS transconductance cell based on composite cells

This paper describes a novel circuit design technique for low-voltage CMOS operational transconductance amplifiers (OTA) based on CMOS square-law composite cells. This cell is used as a main building block to achieve accurate signal processing with low-power dissipation under low-voltage condition. Two pairs of this cell are connected in parallel to achieve rail-to-rail input voltage range. The transconductances of each pairs are inherently tunable by a biasing voltage. The constant-g_m characteristic is controlled by applying suitable values to these biasing voltages maintaining the smooth response over the change of input common mode voltage. HSPISE simulations show that the overall transconductance has linearity better than 6 percent with 2.5 V supply voltage.