The present technology relates to a solid-state imaging device, an electronic apparatus, and an AD converter that are capable of suppressing the occurrence of an error in AD conversion results.The solid-state imaging device includes a pixel section having a plurality of pixels, a comparator for comparing a pixel signal outputted from the pixels with a reference signal, and a counter for counting the time of comparison made by the comparator. The comparator includes a first amplifier for comparing the pixel signal with the reference signal, a second amplifier that has a first transistor and amplifies an output signal of the first amplifier, and a second transistor having the same polarity as the first transistor. A gate of the second transistor is connected to an output end of the first amplifier, and a source and a drain of the second transistor are connected to the same fixed potential as a source of the first transistor. The present technology is applicable, for example, to a CMOS image sensor.