Variable gain correlated double sampling circuit and control method

Abstract

The invention relates to a variable gain correlated double sampling circuit and a control method. The variable gain correlated double sampling circuit is provided with a switch K1, a switch K2, a switch K3, a switch K4, a switch K5, a switch K2_b, a switch K3_b, a switch K4_b, a switch K5_b, a capacitor C1, a capacitor C2, an operational amplifier OPA and a variable gain control module G, and is also provided with a circuit with a symmetrical structure: a node A' is symmetrical with the node A, a node B' is symmetrical with the node B, a node C' is symmetrical with the node C, a node D' is symmetrical with the node D, and a node E' and a node E are symmetrical; the circuit structure located at the in-phase input end of the operational amplifier is the same as the circuit structure located at the anti-phase input end of the operational amplifier, the in-phase output end of the operational amplifier outputs a signal VOUTP, and the anti-phase output end of the operational amplifier outputs a signal VOUTN. Parallel work of the sampling circuit and the holding and amplifying circuit is realized, pixel correction is not needed, and subsequent image processing work is simplified. And after the differential signal is amplified, the post-stage numerical quantization ADC index requirement is reduced.

Description

technical field [0001] The invention relates to the technical field of image sensor chip signal processing, in particular to a variable-gain correlated double-sampling circuit and a control method. Background technique [0002] Correlated double sampling (also known as correlated double sampling, referred to as CDS) circuit does not directly measure the output voltage of each pixel in the image sensor array after exposure, but measures the output voltage twice during the exposure of each pixel: the first measurement is sampled at the beginning of the exposure; the second measurement is sampled at the end of the exposure. The output of the correlated double sampling circuit is the voltage difference measured by the two samples, such as figure 1 As shown, since the output of the front-end circuit of the image sensor is superimposed with interference noise such as FPN (fixed pattern noise), Flicker Noise (low-frequency flicker noise) and Thermal Noise (thermal noise), the FPN ...

AI Technical Summary

Problems solved by technology

Faced with fast-moving objects, it will make pixel correction work difficult

Due to the presence of noise, a self-noise of 76uV RMS Take the digital acquisition system (including ADC) as an example, if the effective range of the input is 2v, then its effective accuracy is less than 15 bits

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