LAUSR

This paper presents a discrete-time low-noise amplifier for miniaturized sensor nodes. Such amplifier achieves a noise efficiency factor of 1.01 and a power efficiency factor of 1.63, improving the noise efficiency of an analog front-end. The proposed preamplifier employs discrete-time parametric amplification by modulating the capacitance of a MOS varactor. The sampling noise is minimized by adopting a high oversampling ratio of the input voltage, leading to an input-referred noise of 520 nVrms in a 1 kHz bandwidth. Also, the power consumption is reduced by using a 34-phase stepwise charging technique. The multiphase soft-charging technique is implemented using multiple time-interleaved cells and allows to significantly reduce the current consumption without introducing any significant penalty in terms of additional noise or area occupation. A two-stage parametric amplifier is introduced to provide higher gain, and suppress the noise contribution of the following amplifier chain. The proposed two-stage complementary preamplifier is followed by a third continuous-time stage, that employs a current-reuse inverter-based architecture. The contribution to the total noise efficiency factor of such amplifier is attenuated by the gain of the previous two-stage parametric preamplifier. As a result, the third stage provides gain programmability, while degrading the NEF of the entire chain by less than 10%.