Linearity efficiency factor and power-efficient operational transconductance amplifier in subthreshold operation

A linearity efficiency factor (LEF) is proposed in this paper to quantify the trade-off among linearity, bandwidth, and power consumption in designing differential pair or operational transconductance amplifier (OTA) circuits. The unitless LEF can be used to evaluate the trade-off efficiency of a circuit topology without considering the effects of input attenuation nor the bias current level when all transistors are biased in the subthreshold region. According to this proposed figure of merit, a power-efficient linearized differential pair and a fully differential OTA are proposed and evaluated. The OTA, which is composed of a complementary pair of the linearized differential pairs and a floating-gate common-mode feedback scheme, exhibits 7.8 times better power efficiency than a basic OTA with capacitive input attenuation while achieving the same transconductance and linearity performance.