# A Low-Noise CMOS Transimpedance-Limiting Amplifier for Dynamic Range Extension

## TL;DR

This paper introduces a low-noise CMOS amplifier for LiDAR sensors that improves power efficiency and extends dynamic range.

## Contribution

A dual-feedback CMOS transimpedance-limiting amplifier that enables automatic limiting without signal distortion.

## Key findings

- The CTLA achieves a transimpedance gain of 88.8 dBΩ and a noise current spectral density of 2.31 pA/√Hz.
- The design provides an input dynamic range of 56.6 dB with a power dissipation of 23.6 mW.
- The chip core is compact, measuring 180 × 50 µm2, and fabricated in a 180 nm CMOS process.

## Abstract

This paper presents a low-noise CMOS transimpedance-limiting amplifier (CTLA) for application in LiDAR sensor systems. The proposed CTLA employs a dual-feedback architecture that combines the passive and active feedback mechanisms simultaneously, thereby enabling automatic limiting operations for input photocurrents exceeding 100 µApp (up to 1.06 mApp) without introducing signal distortions. This design methodology can eliminate the need for a power-hungry multi-stage limiting amplifier, hence significantly improving the power efficiency of LiDAR sensors. The practical implementation for this purpose is to insert a simple NMOS switch between the on-chip avalanche photodiode (APD) and the active feedback amplifier, which then can provide automatic on/off switching in response to variations of the input currents. In particular, the feedback resistor in the active feedback path should be carefully optimized to guarantee the circuit’s robustness and stability. To validate its practicality, the proposed CTLA chips were fabricated in a 180 nm CMOS process, demonstrating a transimpedance gain of 88.8 dBΩ, a −3 dB bandwidth of 629 MHz, a noise current spectral density of 2.31 pA/√Hz, an input dynamic range of 56.6 dB, and a power dissipation of 23.6 mW from a single 1.8 V supply. The chip core was realized within a compact area of 180 × 50 µm2. The proposed CTLA shows a potential solution that is well-suited for power-efficient LiDAR sensor systems in real-world scenarios.