High Sensitivity and Wide Dynamic Range Analog Front-End Circuits for Pulsed TOF 4-D Imaging LADAR Receiver

Abstract

Analog front-end (AFE) circuits, which mainly consist of a transimpedance amplifier (TIA) with wide dynamic range and a timing discriminator with double threshold voltage, were designed and implemented for a pulsed time-of-fight 4-D imaging LADAR receiver. The preamplifier of the proposed TIA adopts a shunt-feedback topology to amplify weak echo signal, and a current-mirror topology to amplify strong one, respectively. The proposed AFE can capture directly the pulsed echo amplitude with wide dynamic range through programmable gain control switches. The proposed AFE circuits, which achieve a high gain of 106 dB $\Omega $ , a linear dynamic range of 80 dB, an averaged input-referred noise density of 0.89 pA/Hz0.5 and a minimum detectable signal of $0.36~\mu \text{A}$ at SNR = 5, and a sensitivity of 8 nW with APD of 45 A/W, were designed with 3.3 V devices and fabricated in a 0.18- $\mu \text{m}$ standard CMOS process. The total area of AFE, which includes the circuit core, bandgap and bias circuits, and I/O PAD, is approximately equal to $1.20\times 1.13$ mm2.