Image sensor, electronic apparatus, comparator, and drive method

Abstract

The present technology relates to an image sensor, an electronic apparatus, a comparator, and a drive method which enable achievement of a noise reduction while maintaining high speed of AD conversion. An ADC for performing AD conversion for an electrical signal output from a pixel includes a comparator that compares the electrical signal and a reference signal, a level of which is changed and a counter that counts time necessary for a change of the reference signal to a coincidence of the electrical signal and the reference signal on the basis of output signals from the comparator. The comparator includes a differential amplifier that outputs a comparison result signal indicating a comparison result obtained by comparing the electrical signal and the reference signal and a plurality of output amplifiers that outputs signals obtained by amplifying the comparison result signal output from the differential amplifier as the output signals at different timings. The present technology can be applied to, for example, an ADC that performs AD conversion for an electrical signal output from a pixel.

1 . An image sensor, comprising:
 a pixel that has a photoelectric conversion element for performing photoelectric conversion and outputs an electrical signal;   a reference signal output unit that outputs a reference signal, a level of which is changed; and   an ADC that performs AD (Analog Digital) conversion for the electrical signal by counting time necessary for a change of the reference signal to a coincidence of the electrical signal output from the pixel and the reference signal output from the reference signal output unit, wherein   the ADC includes
 a comparator that compares the electrical signal with the reference signal, and 
 a counter that counts time necessary for a change of the reference signal to a coincidence of the electrical signal and the reference signal on the basis of output signals from the comparator, and 
 the comparator includes
 a differential amplifier that outputs a comparison result signal indicating a comparison result obtained by comparing the electrical signal and the reference signal, and 
 a plurality of output amplifiers that outputs, at different timings, signals obtained by amplifying the comparison result signal output from the differential amplifier as the output signals. 
 
   
     
     
         2 . The image sensor according to  claim 1 , wherein
 the plurality of output amplifiers outputs the output signals at the different timings by using a difference of bias currents that flow in transistors constituting the plurality of output amplifiers.   
     
     
         3 . The image sensor according to  claim 2 , wherein
 the ADC includes a plurality of counters, the number of which is the same as that of the plurality of output amplifiers.   
     
     
         4 . The image sensor according to  claim 3 , wherein
 one of the plurality of counters counts differential time from time counted by a different counter.   
     
     
         5 . The image sensor according to  claim 2 , wherein
 the pixel has a pixel value determined by adding a plurality of AD conversion results of the electrical signal, which are obtained with respect to the output signals from the plurality of output amplifiers.   
     
     
         6 . A drive method, comprising:
 outputting, by a plurality of output amplifiers of an image sensor, signals obtained by amplifying a comparison result signal output from a differential amplifier as output signals at different timings, the image sensor including   a pixel that has a photoelectric conversion element for performing photoelectric conversion and outputs an electrical signal,   a reference signal output unit that outputs a reference signal, a level of which is changed, and   an ADC that performs AD (Analog Digital) conversion for the electrical signal by counting time necessary for a change of the reference signal to a coincidence of the electrical signal output from the pixel and the reference signal output from the reference signal output unit,   the ADC including
 a comparator that compares the electrical signal with the reference signal, and 
 a counter that counts time necessary for a change of the reference signal to a coincidence of the electrical signal and the reference signal on the basis of the output signals from the comparator, 
 the comparator including
 the differential amplifier that outputs the comparison result signal indicating a comparison result obtained by comparing the electrical signal and the reference signal, and 
 the plurality of output amplifiers that outputs signals obtained by amplifying the comparison result signal output from the differential amplifier as the output signals. 
 
   
     
     
         7 . An electronic apparatus, comprising:
 an optical system that collects light; and   an image sensor that receives light and takes an image, wherein   the image sensor includes
 a pixel that has a photoelectric conversion element for performing photoelectric conversion and outputs an electrical signal, 
 a reference signal output unit that outputs a reference signal, a level of which is changed, and 
 an ADC that performs AD (Analog Digital) conversion for the electrical signal by counting time necessary for a change of the reference signal to a coincidence of the electrical signal output from the pixel and the reference signal output from the reference signal output unit, 
 the ADC includes
 a comparator that compares the electrical signal with the reference signal, and 
 a counter that counts time necessary for a change of the reference signal to a coincidence of the electrical signal and the reference signal on the basis of output signals from the comparator, and 
 the comparator includes
 a differential amplifier that outputs a comparison result signal indicating a comparison result obtained by comparing the electrical signal and the reference signal, and 
 a plurality of output amplifiers that outputs, at different timings, signals obtained by amplifying the comparison result signal output from the differential amplifier as the output signals. 
 
 
   
     
     
         8 . A comparator, comprising:
 a differential amplifier that outputs a comparison result signal indicating a comparison result obtained by comparing two signals; and   a plurality of output amplifiers that outputs signals obtained by amplifying the comparison result signal output from the differential amplifier at different timings.