Output circuit for image sensor
AssigneeEastman Kodak Company
InventorEric G. Stevens
Life of this patent
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Abstract
An output circuit for sequentially receiving and converting charge collected in the photoelements of an image sensor and converting such charge into an output voltage. The output circuit includes a buried-channel LDD transistor having gate, source and drain electrodes. The source electrode provides a floating diffusion. When the transistor is turned off, a potential well is provided in the floating diffusion which collects charge. An output source-follower amplifier also employing buried-channel LDD transistors is connected to the floating diffusion and produces the output voltage.
Claims30
An output circuit for sequentially receiving charge and converting such charge collected in photoelements of an image sensor into an output signal which contains noise, said circuit comprising:
- a. a first MOS transistor having a gate electrode, a channel region under the gate electrode, and source and drain electrodes, said source electrode having a highly doped region spaced from the channel region and a more lightly doped region between the highly doped region and the channel region to provide a floating diffusion with reduced capacitance;
- b. means for selectively applying pulses to the gate electrode of said first transistor to reset the potential across said floating diffusion and prepare it to receive charge produced in a photoelement;
- and
- c. an output source-follower amplifier having a second transistor, a gate of which is electrically connected to said floating diffusion, whereby said amplifier produces a change in output voltage in response to charge collected in said floating diffusion with an improved signal to noise ratio.
An output circuit for sequentially receiving charge and converting such charge collected in photoelements of an image sensor into an output signal which contains noise, said circuit comprising:
- a. a first transistor having a gate electrode, a channel region under the gate electrode, and source and drain electrodes, said source electrode providing a floating diffusion with reduced capacitance;
- b. means for selectively applying pulses to the gate electrode of said first transistor to effect the operating characteristics of said first transistor to reset the potential across the floating diffusion preparing it to receive charge produced in a photoelement;
- c. an output source-follower amplifier having a second transistor, a gate of which is electrically connected to said floating diffusion, whereby said amplifier produces a change in output voltage in response to charge collected in said floating diffusion with an improved signal to noise ratio;
- and
- d. said second transistor comprises a substrate, a channel region in the substrate, an insulating layer on the channel region, a gate electrode on said insulating layer and over the channel region, and highly doped source and drain electrodes in the substrate and each spaced from the channel region by a more lightly doped regions.
The output circuit as set forth in claim wherein the second transistor is a MOS transistor comprising a gate electrode, a channel region under the gate electrode, highly doped source and drain regions at opposite sides of the channel region and a more lightly doped region between the highly doped drain region and the channel region of the second transistor.
An image sensor comprising:
- a substrate of a semiconductor material having a surface;
- a plurality of photoelements in said substrate and extending to the surface thereof;
- a horizontal charge-coupled device in the substrate and extending to the surface to which the photoelements are connected and having an output gate and a channel region under the output gate;
- an output circuit connected to the channel region under the output gate, the output circuit comprising:
- a first MOS transistor having spaced source and drain regions in the substrate and extending to the a gate electrode over and insulated from the surface of the substrate and between the source and drain regions, and a channel region in the substrate under the gate electrode, the source region having a highly doped region in the substrate and spaced from the channel region and a more lightly doped region in the substrate between the highly doped region and the channel region to provide a floating diffusion with reduced capacitance;
- and
- means connecting the floating diffusion to the channel region under the output gate of the horizontal charge-coupled device.
An image sensor comprising:
- a substrate of a semiconductor material having a surface;
- a plurality of photoelements in said substrate and extending to the surface thereof;
- a horizontal charge-coupled device in the substrate and extending to the surface to which the photoelements are connected and having an output gate and a channel region under the output gate;
- an output circuit connected to the channel region under the output gate, the output circuit comprising:
- a first MOS transistor having spaced source and drain region in the substrate and extending to the surface, a gate electrode over and insulated from the surface of the substrate and between the source and drain region, and a channel region in the substrate under the gate electrode, the source region having a highly doped region in the substrate to provide a floating diffusion;
- and
- a lightly doped region in the substrate and extending to the surface and extending between the floating diffusion and the channel region under the output gate to connect the floating diffusion to the channel region under the output gate of the horizontal charge-coupled device.
Dependencies are inferred from the claim text.