线性碲镉汞APD的高速焦平面读出电路研究

Research on High-Speed Circuit of Line-Mode HgCdTe APD

摘要:

设计了一款针对线性模式碲镉汞APD的高速成像读出电路。像元内基于三级推挽放大器级联的电阻反馈跨导放大器(RTIA),实现了光电流的实时线性转换,并利用工作于亚阈值区的MOS管作为反馈电阻实现跨阻增益可调；利用电容补偿法对RTIA的相位裕度进行优化,解决了低增益下的输出振荡现象。结果显示,像元内RTIA跨阻增益可调范围达100~140dB,增益带宽积可达10¹⁴数量级,像元电路输出延时低于1.8ns。设计了像素外的飞行时间测量电路,采用两段式时间数字转换器分别进行飞行时间的大范围粗量化和高精度细量化,测量范围可达1530m,测量精度为106.5cm,线性度高于99.99%。

Abstract:

A high-speed imaging readout circuit for a linear-mode HgCdTe APD was proposed. A resistive feedback transimpedance amplifier (RTIA) with adjustable transimpedance gain was used in the image element to realize the real-time linear conversion of the photocurrent, and the phase margin of the RTIA was optimized using the capacitive compensation method to solve the output oscillation phenomenon at low gain. The results showed that the RTIA transimpedance gain within the image element was 100~140dB, the GBW could be improved by 10¹⁴ times, and the output delay of the image circuit was lower than 1.6ns. A column-level time-of-flight measurement circuit and a two-stage time-to-digital converter were used for the wide-area coarse quantization of the time-of-flight and high-precision fine quantization, respectively. The measurement range was up to 1530m, with a measurement accuracy of 106.5cm and a linearity of greater than 99.99%.