US Patent 9900539 Solid-state image pickup element, and image pickup system

Provided is a solid-state image pickup element including: a plurality of pixels arranged in a pixel well region; a readout circuit arranged in a peripheral well region, having a first input terminal for receiving the pixel signals from the plurality of pixels and a second input terminal for receiving a reference signal; and a reference signal circuit arranged in the peripheral well region, having a first electrode to which a ground voltage is supplied, and being configured to output the reference signal to the second input terminal of the readout circuit, wherein a resistance value R1 of an electrical path from one of a plurality of pixel well contacts to the first electrode and a resistance value R2 of an electrical path from one of a plurality of peripheral well contacts closest to the first electrode to the first electrode satisfy a relationship of R1<R2.