An On-Chip AC Coupled AFE With Asymmetric Output Stage for d-ToF LiDAR

In this brief, an on-chip AC coupled analog front-end circuit with asymmetric output stage is proposed for a pulsed direct time-of-flight LiDAR receiver. The AFE employs a novel on-chip AC coupled scheme for APD cathode bias voltage tuning in a cost-effective manner. A reverse current cancellation circuit helps the circuit recover rapidly under large input current. A transimpedance amplifier is designed for low noise which is desirable to process weak signals. An asymmetric output stage doubles the output swing under the same bias current compared to conventional current mode logic topology. This prototype chip is fabricated in a standard 180 nm CMOS process and the measurement results shows bandwidth, gain, input-referred noise current of 151 MHz, 102 dB<inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\Omega $ </tex-math></inline-formula>, and 3.51 pA/<inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\surd $ </tex-math></inline-formula> Hz, respectively. The maximum differential output swing reaches <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$1.8~\rm V_{\textrm {pp,diff}}$ </tex-math></inline-formula> based on both electrical and optical measurement setup.