A Low Noise and Low Power Two-Stage Charge Amplifier for Automotive Gyroscope Frontends

In this paper, we present a fully differential two-stage charge amplifier for automotive gyroscope frontends. The proposed amplifier features low noise and a low power consumption by utilizing a class AB output stage while also providing a rail-to-rail output voltage swing for a maximum signal-to-noise ratio (SNR). The frequency compensation is realized by using split-length transistors, offering a small compensation capacitance and a high unity gain frequency (UGF). Compared to prior works, our design features the lowest reported total harmonic distortion (THD), lowest gain and phase drift over the automotive temperature range, while occupying the smallest area thanks to the power efficient class AB output stage and frequency compensation scheme. The proposed design has been verified by simulating an extensive corner set consisting of process, temperature and sensor sensitivity variations. The total simulated power consumption of the amplifier stays below 32 <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\mu \mathrm{W}$</tex> with a 1.6 V supply while achieving an input-referred thermal noise floor of below 42 <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\text{nV}/\sqrt{\text{Hz}}$</tex>. Additionally, the charge amplifier offers a THD below −56 dB for an output amplitude of 1.2 <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\mathrm{V}_{\text{pp}}$</tex>, a gain and phase drift below 1.6 m% and 3.8 mrad from <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$-40^{\circ}\mathrm{C}$</tex> to 12 <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$5^{\circ}\mathrm{C}$</tex>, respectively. The amplifier is designed in a 40 nm CMOS process and occupies an area of 150 x 115 <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\mu \mathrm{m}^{2}$</tex>.