Linearity Improvement of Bulk Driven Floating Gate OTA Using Cross-Bulk and Quasi-Bulk Techniques

摘要

In this paper, two highly linear OTAs are presented using a combination of three linearization techniques: floating gate, bulk driven, and source degeneration. In the first OTA, bulk driven floating gate MOSFETs are used as input transistors. The input signal given at the bulk terminals of these input transistors are in the opposite phase of the input signal provided to one of the gates of the respective floating gate MOSFET. This cross-coupling method resulted in a highly linear voltage-to-current conversion at the cost of reduced transconductance. In the second proposed OTA, this reduction in transconductance is restored by using novel quasi-bulk floating gate MOSFETs as input transistors while maintaining the improved linearity. Both the OTAs are designed and simulated using 180 nm CMOS design library and powered with +/- 0.5 V dual power supply. The process variation and mismatch effects on both the OTAs are examined using corner and Monte Carlo analysis. The layouts of the proposed OTAs are also presented and workability is confirmed using post-layout simulations.