Amplification with feedback capacitance for photodetector signals

• US 7,291,822 B2
• Filed: 09/15/2006
• Issued: 11/06/2007
• Est. Priority Date: 03/31/2004
• Status: Active Grant

• Current Assignee: Aptina Imaging Corporation (ON Semiconductor Corporation)
• Original Assignee: Micron Technology, Inc.
• Inventors: Rossi, Giuseppe, Fossum, Eric R., Olsen, Alf
• Primary Examiner(s): Epps; Georgia
• Assistant Examiner(s): YAM, STEPHEN K
• Application Number:
  US11/521,350
• Publication Number:
  US 20070007437A1
• Time in Patent Office: 417 Days
• Field of Search: 250/214.A, 250/214.R, 348/300, 348/301
• US Class Current: 250/208.1
• CPC Class Codes: H03F 3/08 controlled by light
• CPC Class Codes: H03F 3/082 with FET's H03F3/085 takes precedence
• CPC Class Codes: H03F 3/087 with IC amplifier blocks H03F3/085 takes precedence
• CPC Class Codes: H04N 25/616 involving a correlated sampling function, e.g. correlated double sampling [CDS] or triple sampling
• CPC Class Codes: H04N 25/75 Circuitry for providing, modifying or processing image signals from the pixel array
• CPC Class Codes: H04N 25/76 Addressed sensors, e.g. MOS or CMOS sensors
• CPC Class Codes: H04N 25/77 Pixel circuitry, e.g. memories, A/D converters, pixel amplifiers, shared circuits or shared components
• CPC Class Codes: H04N 25/779 Circuitry for scanning or addressing the pixel array
• CPC Class Codes: H04N 3/1512 for MOS image-sensors, e.g. MOS-CCD H04N3/1581 takes precedence

Abstract

Signals from an imager pixel photodetector are received by an amplifier having capacitive feedback, such as a capacitive transimpedance amplifier (CTIA). The amplifier can be operated at a low or no power level during an integration period of a photodetector to reduce power dissipation. The amplifier can be distributed, with an amplifier element within each pixel of an array and with amplifier output circuitry outside the pixel array. The amplifier can be a single ended cascode amplifier, a folded cascode amplifier, a differential input telescopic cascode amplifier, or other configuration. The amplifier can be used in pixel configurations where the amplifier is directly connected to the photodetector, or in configurations which use a transfer transistor to couple signal charges to a floating diffusion node with the amplifier being coupled to the floating diffusion node.

Claims

1. A method of operating a pixel cell, the method comprising:

providing first and second bias voltages to operate a capacitive transimpedance amplifier;

generating charges with a photodetector during an integration period;

resetting a charge storage node that receives photo generated charges generated by said photodetector to a reset level;

with the storage node at the reset level, reading and sampling a first output signal from said capacitive transimpedance amplifier having an input coupled to said storage node;

opening a first switch circuit to float a reset line;

closing a second switch circuit to connect the capacitive transimpedance amplifier input to an output stage of the capacitive transimpedance amplifier and to operate said capacitive transimpedance amplifier during a readout operation;

receiving charges at said charge storage node generated by said photodetector during said integration period; and

reading and sampling a second output signal from said capacitive transimpedance amplifier after said integration period.

2. The method of claim 1 further comprising controlling said second switch circuit by pulsing a row select line.

3. The method of claim 1 further comprising operating at least a portion of said capacitive transimpedance amplifier outside of said pixel cell.

4. The method of claim 1 further comprising operating a portion of said capacitive transimpedance amplifier outside of said pixel cell and operating a portion of said capacitive transimpedance amplifier inside said pixel cell.

5. The method of claim 1 further comprising operating said capacitive transimpedance amplifier within said pixel cell.

6. The method of claim 1 further comprising controlling a charge transference from the photodetector to said storage node with a transfer transistor.