A CMOS AFE Array With DC Input Current Cancellation for FMCW LiDAR

This article presents a low noise and wide linear dynamic 20-channel analog front-end (AFE) array for frequency-modulated continuous-wave (FMCW) light detection and ranging (LiDAR) system. Each channel of the AFE array mainly consists of a shunt feedback transimpedance amplifier (SF-TIA) with a dc cancellation loop (DCL), a post amplifier, and an output buffer. The DCL is proposed to eliminate the dc current, comprising the dc current sunk to ground (dc-STG) and the dc current sourced from power supply (dc-SFP). In addition, the post amplifier, cascaded with an operational transconductance amplifier (OTA) and an SF-TIA, is proposed to decouple the relationship between gain and output common voltage, achieving both large gain and large output swing. Furthermore, the equalization technique is adopted to expand the bandwidth of the AFE array. The AFE array was implemented and fabricated in a 0.18- m CMOS technology. Measurement results show that the AFE array achieves the maximum transimpedance gain of 107 dB and eliminates the dc current between -150 and 250 mu A A. With the maximum transimpedance gain, the measured bandwidth, the equivalent input-referred rms noise current, and the signal-to-crosstalk ratio (SCR) between adjacent channels are 165 MHz, 29.4 nArms, and $-$ 33.9 dB, respectively. The AFE array also achieves a linear dynamic range (DR) of 66 dB and the area of each channel is approximately equal to 0.16x1.3 mm(2).