Image sensors with low-voltage transistors

1. An image sensor, comprising:

an image pixel configured to generate an analog image signal in response to incident light;

readout circuitry coupled to the image pixel via a pixel output line;

processing circuitry coupled to the readout circuitry via an image output path; and

power supply circuitry coupled to the readout circuitry using a first power rail and a second power rail, and coupled to the processing circuitry using the second power rail and a third power rail, wherein the first power rail supplies a first voltage level, the second power rail supplies a second voltage level that is at a lower voltage than the first voltage level, the third power rail supplies a third voltage level that is at a lower voltage than the second voltage level.

2. The image sensor defined in claim 1 , wherein the readout circuitry comprises transistors that receive only signals having voltages between the first voltage level and the second voltage level.

3. The image sensor defined in claim 2 , wherein the transistors in the readout circuitry have respective substrate body terminals, each biased to one of the first and second voltage levels.

4. The image sensor defined in claim 3 , wherein the processing circuitry comprises transistors that receive only signals having voltages between the second voltage level and the third voltage level.

5. The image sensor defined in claim 4 , wherein the transistors in the processing circuitry have respective substrate body terminals, each biased to one of the second and third voltage levels.

6. The image sensor defined in claim 1 , wherein the readout circuitry comprises analog circuitry and is configured to receive the analog image signal and convert the analog image signal into digital image data.

7. The image sensor defined in claim 6 , wherein the processing circuitry comprises digital circuitry and is configured to receive the digital image data from the readout circuitry.

8. The image sensor defined in claim 7 , wherein the readout circuitry comprises sample and hold circuitry and the sample and hold circuitry is configured to receive a reference voltage that is at a same voltage as the second voltage level.

9. The image sensor defined in claim 1 , wherein the third voltage level is a grounding voltage level.

10. The image sensor defined in claim 1 , wherein the readout circuitry is operable in a first voltage domain defined by the first and second voltage levels, and the processing circuitry is operable in a second voltage domain defined by the second and third voltage levels.

11. Image sensor circuitry, comprising:

an image pixel configured to generate an analog image signal in response to incident light;

analog circuitry having a first transistor configured to operate using a first set of voltages between a first voltage level and a second voltage level, wherein the first transistor includes a body terminal that is biased to the second voltage level; and

digital circuitry having a second transistor configured to operate using a second set of voltages between the second voltage level and a third voltage level, wherein the second transistor includes a body terminal that is biased to the third voltage level.

12. The image sensor circuitry defined in claim 11 , wherein the third voltage level is at a ground voltage and the second voltage level is at a voltage higher than the ground voltage.

13. The image sensor circuitry defined in claim 11 , wherein the third voltage level is at a voltage higher than the voltage of the second voltage level.

14. The image sensor circuitry defined in claim 11 , wherein the analog circuitry is interposed between the image pixel and the digital circuitry.

15. The image sensor circuitry defined in claim 14 , further comprising:

a current source configured to generate a current on a pixel output line while receiving the first voltage level and the second voltage level, wherein the pixel output line couples the image pixel to the analog circuitry.

16. An imaging system, comprising:

at least one lens;

an array of image sensor pixels, wherein the at least one lens focuses image light onto the array of image sensor pixels and wherein the image sensor pixels are configured to generate analog image signals in response to the image light;

readout circuitry coupled to the array of image sensor pixels and configured to operate in a first voltage level domain, wherein the first voltage level domain includes an intermediate voltage level that defines a minimum voltage level in the first voltage level domain; and

processing circuitry coupled to the readout circuitry and configured to operate in a second voltage level domain, wherein the second voltage level domain includes the intermediate voltage level that defines a maximum voltage level in the second voltage level domain.

17. The imaging system defined in claim 16 , further comprising:

a first power supply rail configured to provide a first voltage level to the readout circuitry; and

a second power supply rail configured to provide a second voltage level to the readout circuitry, wherein the first voltage level domain is defined by voltages between the first and second voltage levels and the second voltage level comprises the intermediate voltage level.

18. The imaging system defined in claim 17 , further comprising:

a third power supply rail configured to provide a third voltage level to the processing circuitry, wherein the second power supply rail is configured to provide the second voltage level to the processing circuitry and the second voltage level domain is defined by voltages between the second and third voltage levels.

19. The imaging system defined in claim 18 , wherein the third voltage level comprises a ground voltage level and the second voltage level comprises a voltage level above the ground voltage level.