Methods and apparatus for a light sensor
Various embodiments of the present technology may comprise methods and apparatus for a light sensor with a precharge circuit, such as for charging an internal node of a sensor to a starting voltage equal to an ending voltage of a different sensor. The methods and apparatus may comprise sequentially reading out the voltages of photosensitive elements and selectively activating the precharge circuit of one sensor during readout of the last photosensitive element of a different sensor.
1. A sensor comprising:
a plurality of photosensitive elements;
a plurality of switchable first-stage amplifiers, wherein each switchable first-stage amplifier is coupled directly between one of the photosensitive elements and a common node;
a switchable second-stage amplifier coupled between the common node and an output bus; and
a precharge circuit coupled between the output bus and the common node.
2. The sensor of claim 1 , wherein each switchable first-stage amplifier comprises a first switching device.
3. The sensor of claim 2 , wherein the switchable second-stage amplifier comprises a second switching device.
4. The sensor of claim 3 , further comprising a third switching device, wherein the third switching device selectively couples an output terminal of the precharge circuit to the common node.
5. The sensor of claim 3 , further comprising a third switching device, wherein the third switching device selectively couples the output bus to an input terminal of the precharge circuit.
6. The sensor of claim 1 , wherein the switchable second-stage amplifier has a voltage gain of less than 1.
7. The sensor of claim 6 , wherein the precharge circuit comprises an amplifier with a voltage gain equal to the inverse of the voltage gain of the second-stage amplifier.
8. The sensor of claim 1 , wherein the plurality of photosensitive elements is arranged in a linear array.
9. The sensor of claim 1 , wherein the precharge circuit is formed on a same chip as the plurality of photosensitive elements.
10. A light sensor system, comprising:
a plurality of sensors coupled via an output bus, wherein at least one sensor comprises:
a plurality of photosensitive elements;
a plurality of switchable first-stage amplifiers, wherein each switchable first-stage amplifier is coupled between one of the photosensitive elements and a common node;
a switchable second-stage amplifier, wherein an input terminal of the switchable second-stage amplifier is coupled to the common node and an output terminal of the switchable second-stage amplifier is coupled to an output bus; and
a precharge circuit, wherein an input terminal of the precharge circuit is coupled to the output bus and an output terminal of the precharge circuit is coupled to the common node.
11. The light sensor system of claim 10 , wherein each switchable first-stage amplifier comprises a first switching device.
12. The light sensor system of claim 11 , further comprising a control unit, wherein the control unit sequentially activates the first switching devices.
13. The light sensor system of claim 10 , wherein the plurality of photosensitive elements is arranged in a linear array.
14. The light sensor system of claim 10 , wherein the switchable second-stage amplifier has a voltage gain of less than 1.
15. The light sensor system of claim 14 , wherein the precharge circuit comprises an amplifier with a voltage gain equal to the inverse of the voltage gain of the second-stage amplifier.
16. The light sensor system of claim 10 , wherein the precharge circuit is formed on a same chip as the plurality of photosensitive elements.