Implementation of a Multipath Fully Differential OTA in 0.18-mu m CMOS Process

This brief implements a highly efficient fully differential transconductance amplifier, based on several input-to-output paths. Some traditional techniques, such as positive feedback, nonlinear tail current sources, and current mirror-based paths, are combined to increase the transconductance, thus leading to larger dc gain and higher gain bandwidth (GBW) product. Two flipped voltage-follower (FVF) cells are employed as variable current sources to provide class-AB operation and adaptive biasing of all other drivers. The proposed structure includes several input-to-output paths that play the role of dynamic current boosters during the slewing phase, thus improving the slew rate (SR) performance. The circuit was fabricated in a TSMC 0.18-mu m CMOS process with a silicon area of 54.5 x 30.1 mu m. Experimental results show a GBW of 173.3 MHz, a dc gain of 72.7 dB, and an SR of 139.4 V/mu s for a capacitive load of 2 x 5 pF. The proposed circuit consumes 619 mu W of power, under a supply voltage of 1.8 V.