# A Current-Mode Optoelectronic Receiver IC for Short-Range LiDAR Sensors in 180 nm CMOS
## 5 Measured Results of the Proposed C-OER
### Measured Results  
Figure 17 demonstrates the optically measured pulse responses of the proposed C-OER IC for two different on-chip APDs with two different input pulses, where it is clearly seen that the C-OER integrated with the P\({}^{+}\)/NW APD exhibits relatively much larger output voltages than the case with the P\({}^{+}\)/DNW APD. Here, it is noted that the P\({}^{+}\)/NW/DNW APD was not integrated in this C-OER IC even with its highest responsivity because this might saturate the output voltages even at a much smaller input current than 1 mA\({}_{\text{pp}}\), i.e., the limited input dynamic range. Therefore, the P\({}^{+}\)/NW APD would be the most appropriate detector, not only to extend the input dynamic range further, but also to recover the weak input currents of 5 mA\({}_{\text{pp}}\) well enough. Figure 16: Chip photo of the C-OER IC and its test module. Figure 15: Simulated pulse responses of the proposed C-OER IC: (**a**) with small (5–100 \(\mu\)A\({}_{\text{pp}}\)), (**b**) with large (0.2–1 mA\({}_{\text{pp}}\)) input currents, respectively. Table 2 compares the performance of the C-OER IC with the previously reported CMOS receivers for short-range LiDAR sensors. Ref. [14] suggested a current-mirror (CM) input configuration with a shunt-feedback (SF) topology, which could successfully attain high transimpedance gain and wide dynamic range. However, the AGC function was carried out by an external field programmable gate array (FPGA). Ref. [15] merged a voltage-mode feedforward input configuration with a negative feedback AGC circuit comprising four switches so as to extend the dynamic range. However, it exploited off-chip APDs and the AGC circuit could not recover the input pulses within a single-pulse width. Ref. [16] proposed a capacitive feedback (CF) topology to obtain nanoampere low-noise currents. However, the manual gain control was required for low-gain and high-gain modes, and the maximum current detectable in the loop was limited to 250 \(\mu\)A\({}_{\text{PP}}\). Ref. [17] achieved a wide bandwidth with a current-amplifier-based feedback configuration (CAF) by a pole-zero cancellation technique. Nevertheless, the AGC function was conducted by using an external control. Yet, the detectable current range was limited from 23 \(\mu\)A\({}_{\text{PP}}\) to 83 \(\mu\)A\({}_{\text{PP}}\). \begin{table}
\begin{tabular}{c c c c c c c} \hline \hline
**PARAMETERS** & [14] & [15] & [16] & [17] & **V-OER** & **C-OER** \\ \hline CMOS technology (nm) & 180 & 180 & 350 & 180 & 180 & 180 \\ \hline Supply (V) & 3.3 & 1.8 & 3.3 & 1.8/3.3 & 1.8 & 1.8/3.3 \\ \hline APD & On-chip & Off-chip & On-chip & Off-chip & On-chip & On-chip \\ \hline Input configuration & CM + SF & VCF & CF & CAF & VCF & CCIB \\ \hline Output signaling & single-ended & differential & single-ended & differential & differential \\ \hline Bandwidth (MHz) & 153 & 720 & 160 & 1000 & 608 & 151–229 \\ \hline TZ gain (dB\(\Omega\)) & 106 & 76.3 & 78–110 & 56.8–69.3 & 95.1 & 61–83.1 \\ \hline Gain control & External & Auto & External & External & No & Auto \\ \hline Max. detectable current & 5.0 & 1.1 & 0.022 & 0.083 & 0.05 & 1.0 \\ (m\({}_{\text{PP}}\)) & & & & & & \\ \hline Min. detectable current & 0.5 & 1.14 & 0.053 & 23 & 2.38 & 5.0 \\ (m\({}_{\text{PP}}\)) & (SNR = 5) & (SNR = 12) & (SNR = 3.3) & (SNR = 14) & (SNR = 10) & (SNR = 14) \\ \hline Power dissipation (mW) & 16.5(w/o OB) & 29.8 & 79 & 6.6(w/o OB) & 39.3(w/OB) & 47.8 \\ \hline Core area (mm\({}^{2}\)) & 1.2 \(\times\) 1.13 & 5.0 \(\times\) 1.1 & 1.0 \(\times\) 1.2 & 0.1 \(\times\) 0.075 & 0.068 & 0.28 \(\times\) 0.31 \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Performance Comparison with Previously Reported CMOS Receivers for LiDAR Sensors. Figure 17: Optically measured pulse responses of the proposed C-OER IC with two different APDs for (**a**) 50 ns and (**b**) 100 ns input pulses. In this proposed C-OER IC, we have realized the variable AGC mechanism within a narrow single-pulse width by employing FRA feedforward gain control.