Pixel reset circuit is an important component of CMOS image sensor, whose characteristics affect the image quality directly. The performances of CMOS image sensor, such as dynamic range, anti-blooming, image lag and non-linearity, are analyzed. This paper also discusses the methods to improve performance through reset circuit. In this paper, two kinds of hard reset circuit with anti-blooming circuit are designed, one is the use of conventional cross-coupled configuration to implement reset level shift, the other is based on improved latch configuration with adding compensation transistor of threshold value, both schemes with different advantages and disadvantages adapt for different applications. The simulations reveal that both circuits implement can enhance dynamic range by 2 dB~3 dB, increase the ability of anti-blooming, and remove image lag and non-linearity at low-light level.

This paper presents an improved double delta sampling (DDS) circuit and the architecture and readout sequence are introduced in detail. Meanwhile, a new method to evaluate the Fixed Pattern Noise (FPN) cancellation for readout circuit before fabricated is proposed. Thus, we can evaluate DDS or other readout circuit in another view. Compared with the conventional DDS circuit, the new architecture is better overall performance. Simulation results indicate the improved DDS circuit can achieve SNR (Signal Noise Ratio) of 72.12 dB and SFDR (Spurious Free Dynamic Range) of 73.39 dB with a sampling frequency of 10MHz. Through the proposed method, we calculated that the level of FPN cancellation achieves 11.6 bits on average and 15.2 bits on maximum.

Pixel reset circuit is an important component of CMOS image sensor ,whose characteristics affect the image quality directly .To improve the performance of CMOS image sensor ,a high performance reset control circuit was designed based on the principle of CMOS image sensor dual -slope integration reset and hard -soft reset .The circuit can achieve dual - slope integration reset mode , hard - soft reset mode , independent hard reset and independent soft reset .According to different application ,this circuit can implement enhancing dynamic range or reset of low reset noise without image lag .