为提高数字像素图像传感器的动态范围,提出了一种具有自适应参考电压的脉冲宽度调制读出方法。该方法将像素阵列分成包含相同数目像素的像素块,通过参考电压产生模块使每个像素块的参考电压和像素块内光照强度相关,理论上这种结构能够将数字像素图像传感器的动态范围从48 d B提升至96 d B,实际仿真结果为88.16 d B。分析了像素分块内主要的噪声来源和参考电压产生模块的采样电容引入的偏差。采用65 nm CMOS工艺实现了4×4的像素块电路,在高光强和弱光强条件下分别将电路输出同理论计算值相比较,并分析了产生误差的原因。
A low-power-consumption 9bit 10MS/s pipeline ADC,used in a CMOS image sensor,is proposed. In the design, the decrease of power consumption is achieved by applying low-power-consumption and large-output-swing amplifiers with gain boost structure, and biasing all the cells with the same voltage bias source, which requires careful layout design and large capacitors. In addition,capacitor array DAC is also applied to reduce power consumption,and low threshold voltage MOS transistors are used to achieve a large signal processing range. The ADC was implemented in a 0.18μm 4M-1 P CMOS process,and the experimental results indicate that it consumes only 7mW, which is much less than general pipeline ADCs. The ADC was used in a 300000 pixels CMOS image sensor.
用 Monte Carlo法模拟了亚微米 GaAs MESFET的直流特性.不同栅压下源漏电流与源漏电压的关系表明,器件具有较高的跨导.在栅下沟道区和栅漏之间的区域均有较强的电场,使得大量的电子在漏区进入能量较高的X带能谷.电子浓度的分布表明,电子的过冲过程主要发生在栅下沟道区,因而,在这一区域,电子的平均漂移速度较高.但在漏区由于电子处于有效质量大的X带能谷中,因此,在这一区域内,电子的平均漂移速度降低.
