Variable dynamic range pixel sensor cell, design structure and method
AssigneeInternational Business Machines Corporation
InventorsJohn J. Ellis-Monaghan, Mark D. Jaffe, Charles F. Musante
Life of this patent
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Abstract
A pixel sensor cell including a column circuit, a design structure for fabricating the pixel sensor cell including the column circuit and a method for operating the pixel sensor cell including the column circuit are predicated upon the measurement of multiple reference data point and signal data point pairs from a floating diffusion at a variable capacitance. The variable capacitance is provided by excluding or including a transfer gate transistor capacitance in addition to a floating diffusion capacitance. Such a variable capacitance provides variable dynamic ranges for the pixel sensor cell including the column circuit.
Claims25
A pixel sensor cell circuit comprising:
- a photodiode coupled in series with a first source/drain region of a transfer gate transistor;
- a floating diffusion coupled in series with a second source/drain region of the transfer gate transistor;
- a column circuit output coupled to the floating diffusion through a gate of a source follower transistor connected to the floating diffusion, the source follower transistor coupled in series with a row select transistor whose source/drain region provides the column circuit output;
- and
- a column circuit connected to the column circuit output, the column circuit including at least two pass gate transistors having a first source/drain region connected in parallel to the column circuit output, each pass gate transistor further having a second source/drain region connected in series to a separate data storage capacitor.
A design structure embodied in a machine readable medium, the design structure comprising a pixel sensor cell circuit comprising:
- a photodiode coupled in series with a first source/drain region of a transfer gate transistor;
- a floating diffusion coupled in series with a second source/drain region of the transfer gate transistor;
- a column circuit output coupled to the floating diffusion through a gate of a source follower transistor connected to the floating diffusion, the source follower transistor coupled in series with a and row select transistor whose source/drain region provides the column circuit output;
- and
- a column circuit connected to the column circuit output, the column circuit including at least two pass gate transistors having a first source/drain region connected in parallel to the column circuit output, each pass gate transistor further having a second source/drain region connected in series to a separate data storage capacitor.
A method for operating a pixel sensor cell circuit comprising:
- providing a pixel sensor cell comprising:
- a photodiode coupled in series with a first source/drain region of a transfer gate transistor;
- a floating diffusion coupled in series with a second source/drain region of the transfer gate transistor;
- a column circuit output coupled to the floating diffusion through a gate of a source follower transistor connected to the floating diffusion, the source follower transistor coupled in series with a and row select transistor whose source/drain region provides the column circuit output;
- and
- a column circuit connected to the column circuit output, the column circuit including at least two pass gate transistors having a first source/drain region connected in parallel to the column circuit output, each pass gate transistor further having a second source/drain region connected in series to a separate data storage capacitor;
- and
- reading to the separate data storage capacitors at least:
- a first reference charge and a first signal charge from the floating diffusion with the transfer gate transistor off;
- and
- a second reference charge and a second signal charge different from the first signal charge from the floating diffusion with the transfer gate transistor on.
Dependencies are inferred from the claim text.