Image sensor

• US 7,884,402 B2
• Filed: 09/29/2008
• Issued: 02/08/2011
• Est. Priority Date: 11/06/2007
• Status: Active Grant

• Current Assignee: MOSAID Technologies Inc. (f/k/a Conversant Intellectual Property Management)
• Original Assignee: Dongbu HiTek Co., Ltd. (DB HiTek Co., Ltd.)
• Inventors: Ki, An Do
• Primary Examiner(s): Blum; David S
• Application Number:
  US12/239,924
• Publication Number:
  US 20090114961A1
• Time in Patent Office: 862 Days
• Field of Search: 348/272, 257/292, 257/27.132, 257/E27.133 E
• US Class Current: 257/292
• CPC Class Codes: H04N 25/59 by controlling the amount of charge storable in the pixel, e.g. modification of the charge conversion ratio of the floating node capacitance
• CPC Class Codes: H04N 25/771 comprising storage means other than floating diffusion

Abstract

Provided is an image sensor. According to embodiments, the subject image sensor can include a photodiode for converting incident light into electrical signals, a reset transistor for resetting a voltage value of a unit pixel, a drive transistor for providing an output voltage, a select transistor for selecting the unit pixel, a storage capacitor for storing electrons leaking from the photodiode, and a switching transistor for controlling the flow of charge to and from the storage capacitor. The switching transistor can be disposed connected to a node between the photodiode and the reset transistor, and the storage capacitor can be disposed at a side of the switching transistor.

Claims

1. An image sensor comprising:

a photodiode;

a transfer transistor for transferring charges front the photodiode to a floating diffusion region;

a drive transistor for outputting an electric signal depending on charges accumulated in the photodiode;

a reset transistor for resetting a voltage value of a unit pixel before charge transference of the charges accumulated in the photodiode;

a select transistor for selecting the unit pixel from a plurality of unit pixels;

a switching transistor connected at a node between the photodiode and the reset transistor; and

a storage capacitor in series with the switching transistor between a side of the switching transistor and a ground,

wherein a drain of switching transistor is disposed between the floating diffusion and the reset transistor.

2. The image sensor according to claim 1, wherein the switching transistor is connected such that the storage capacitor stores electrons that overflow from the photodiode into the floating diffusion region when the switching transistor is turned on, and outputs the stored electrons to the floating diffusion region as signal electrons for combination with electrons inflowing into the floating diffusion region when the transfer transistor is turned on.

3. The image sensor according to claim 2, wherein turning the switching transistor on transfers the electrons that overflowed from the photodiode into the floating diffusion region to the storage capacitor, and turning the switching transistor off stores the transferred electrons in the storage capacitor.

4. The image sensor according to claim 3, wherein when the transfer transistor is turned on, and electrons flow into the floating diffusion region from the photodiode, the switching transistor is turned on to output the stored electrons from the storage capacitor to the floating diffusion region, combining the stored electrons with the electrons flowing into the floating diffusion region from the photodiode to control the drive transistor.

5. An image sensor comprising:

a photodiode;

a transfer transistor for transferring charges from the photodiode to a floating diffusion region;

a reset transistor connected between the floating diffusion region and a VDD voltage;

a select transistor for selecting a unit pixel;

a drive transistor connected between the VDD voltage and the select transistor, wherein a gate of the drive transistor is connected to the floating diffusion region;

a storage capacitor between a side of the switching transistor and a ground; and

switching transistor connected between the floating diffusion region and the storage capacitor,

wherein the switching transistor is connected at a node between the photodiode and the reset transistor;

wherein a drain of the switching transistor is disposed between the floating diffusion region and the reset transistor.