Image detection apparatus and methods
View Patent ↗MOS imaging pixels are described. The MOS imaging pixels may comprise bootstrapped source followers, having their bodies connected to their sources. The source followers of the MOS imaging pixels may be used to buffer a signal indicative of an amount of radiation incident on the pixel. MOS imagers are also described, which may comprise one or more MOS imaging pixels of the type described.
1. An apparatus comprising:
a first MOS imaging pixel comprising:
a photodetector configured to receive incident radiation and produce a photocurrent in response to the incident radiation;
a MOS field effect transistor (MOSFET) configured as a source follower, the MOSFET having a body, a source, and a gate, the source being directly connected to the body such that they remain at substantially the same electrical potential, and the gate being coupled to the photodetector to receive a voltage signal resulting at least partially from integration of the photocurrent and indicative of an amount of the incident radiation;
a precharge transistor coupled to the photodetector and configured to inject a precharge on the gate of the MOSFET; and
a switch comprising a p-channel transistor and an n-channel transistor, the switch coupled between the source of the MOSFET and a column line and configured to provide a voltage on the source of the MOSFET to the column line,
wherein the column line interconnects a plurality of MOS imaging pixels including the first MOS imaging pixel.
2. The apparatus of claim 1 , wherein the photodetector is configured to detect radiation in the short wavelength infrared spectrum.
3. The apparatus of claim 1 , wherein the first MOS imaging pixel further comprises a substrate of a first conductivity type (n or p), and wherein the body of the MOSFET comprises a well of a second conductivity type (n or p) formed in the substrate, the second conductivity type being opposite the first conductivity type.
4. The apparatus of claim 3 , wherein the MOSFET is a p-channel MOSFET and the well is an n-type well.
5. The apparatus of claim 3 , wherein the MOSFET is an n-channel MOSFET and the well is a p-type well.
6. The apparatus of claim 1 , wherein the apparatus further comprises a substrate and the plurality of MOS imaging pixels including the first MOS imaging pixel, and wherein the plurality of MOS imaging pixels are formed on the substrate and configured in a focal plane array.
7. The apparatus of claim 1 ,
wherein the source follower operates as a buffer having a gain that is at least approximately 0.9.
8. The apparatus of claim 1 , wherein the first MOS imaging pixel has a surface area less than approximately 150 square microns.
9. The apparatus of claim 2 , wherein the photodetector is configured to detect short wavelength infrared (SWIR) radiation having a wavelength in the range from approximately 1.1 microns to approximately 1.6 microns.
10. The apparatus of claim 9 , wherein the photodetector comprises germanium.
11. The apparatus of claim 7 , wherein the gain of the buffer is less than approximately 1.05.
12. The apparatus of claim 11 , wherein the gain of the buffer is at least approximately 0.95.