Apparatus, methods and systems for amplifier

• US 7,990,452 B2
• Filed: 01/31/2007
• Issued: 08/02/2011
• Est. Priority Date: 01/31/2007
• Status: Active Grant

• Current Assignee: Aptina Imaging Corporation (ON Semiconductor Corporation)
• Original Assignee: Aptina Imaging Corporation (ON Semiconductor Corporation)
• Inventors: Yan, Hai
• Primary Examiner(s): Tran; Nhan T
• Application Number:
  US11/700,487
• Publication Number:
  US 20080180559A1
• Time in Patent Office: 1,644 Days
• Field of Search: 348/294, 348/300, 348/302, 348/307, 348/241, 348/317, 330/250, 330/295, 330/255, 330/260, 330/262, 257/159
• US Class Current: 348/300
• CPC Class Codes: H03F 3/45188 Non-folded cascode stages
• CPC Class Codes: H04N 25/00 Circuitry of solid-state image sensors [SSIS]; Control thereof
• CPC Class Codes: H04N 25/67 applied to fixed-pattern noise, e.g. non-uniformity of response
• CPC Class Codes: H04N 25/75 Circuitry for providing, modifying or processing image signals from the pixel array
• CPC Class Codes: H04N 25/766 comprising control or output lines used for a plurality of functions, e.g. for pixel output, driving, reset or power
• CPC Class Codes: H04N 3/1568 for disturbance correction or prevention within the image-sensor, e.g. biasing, blooming, smearing correction circuits H04N25/62

Abstract

Various embodiments comprise apparatus, methods, and systems that include an amplification apparatus comprising a first input, a second input, and an output, a first plurality of series-connected transistors including a first transistor having a first channel ratio and a first gate coupled to the first input, and a second plurality of series-connected transistors including a second transistor having a second channel ratio that is greater than the first channel ratio, the second transistor including a second gate coupled to the second input.

Claims

1. A method comprising:

receiving a first input signal at a first input of an amplification apparatus, the first input coupled to a first transistor having a first channel ratio;

receiving a second input signal at a second input of the amplification apparatus, the second input coupled to a second transistor having a second channel ratio that is approximately N times greater than the first channel ratio, wherein N is greater than or equal to two; and

amplifying the first and second input signals to provide an output signal at an output of the amplification apparatus, wherein the output signal has a gain bandwidth that is determined by approximately twice the value of N divided by N+1.

2. The method of claim 1, wherein amplifying the first and the second input signals includes:

providing the output signal having a slew rate that is approximately proportional to N.

3. The method of claim 1, wherein N has a value of about 5 to about 10.

4. The method of claim 1, wherein receiving the first input signal includes:

receiving the first input signal from a column line coupled to an array of imaging sensors.

5. The method of claim 1, wherein providing the output signal at the output coupled to the second transistor includes the amplification apparatus providing an output current I_out at the output determined by a formula:

I_out≈

V_d*(2*N)/(N+1)*(I_b/Vsat_2nd)

wherein V_d is a differential voltage appearing between the first input and the second input, N is a fraction determined by the second channel ratio and the first channel ratio, I_b is a total bias current of the amplifier, and Vsat_2nd is a saturation voltage of the second transistor.

6. The method of claim 1, wherein providing the output signal includes:

providing a voltage to a sample and hold capacitor representing a difference between the first input signal and a reference voltage provided as the second input signal.

7. The method of claim 1, wherein receiving the second input signal includes:

selecting a pixel from a plurality of pixels, each of the plurality of pixels having an output, and receiving the output of the selected pixel as the second input signal.

8. A system comprising:

a sensor including an array of pixels, the array of pixels including a plurality of columns of pixels, wherein some of the plurality of columns of pixels include a plurality of pixels and a column line coupled to an output of each of the plurality of pixels; and

a plurality of column amplifiers, wherein at least one of the plurality of column amplifiers is coupled to a single one of the column lines at a first column amplifier input and to a voltage reference at a second column amplifier input, wherein the at least one of the plurality of column amplifiers includes a first transistor having a first channel ratio and a first gate coupled to the single one of the column lines, and a second transistor having a second channel ratio that is greater than the first channel ratio, the second transistor including a second gate coupled to the voltage reference, and wherein some of the plurality of column amplifiers provide an output current I_out at an output determined by a formula;

I_out≈

V_d*(2*N)/(N+1)*(I_b/Vsat_2nd)

wherein V_d is a differential voltage appearing between the first column amplifier input and the second column amplifier input, N is a fraction determined by the second channel ratio and the first channel ratio, I_b is a total bias current of the column amplifier, and Vsat_2nd is a saturation voltage of the second transistor.

9. The system of claim 8 including:

a control circuit coupled to at least some of the column lines included in each of the plurality of columns of pixels, the control circuit operable to control an electrical coupling of each of the pixels to one of the first column amplifier inputs.

10. The system of claim 8, wherein some of the plurality of column amplifiers include an output coupled to a readout circuit having a sample and hold capacitor.

11. The system of claim 8, wherein some of the plurality of column amplifiers include a switch coupling an output of the column amplifier to the first column amplifier input of the column amplifier.

12. The system of claim 11, including:

a control circuit coupled to the switch and operable to open and close the switch, wherein closing the switch provides a reset of a value stored in a sample and hold capacitor, and opening the switch provides an amplified sample of an output from one of the plurality of pixels to the sample and hold capacitor.

13. The system of claim 8, wherein the second channel ratio is an integer multiple between about 2 and 11 of the first channel ratio.

14. The system of claim 8, wherein some of the plurality of column amplifiers include a first group of transistors in a first plurality of series-connected transistors having a channel ratio about equal to the first channel ratio, and a second group of transistors in a second plurality of series-connected transistors having a channel ratio about equal to the second channel ratio.

15. The system of claim 8, wherein the sensor includes:

a complementary metal oxide sensor.

16. A system comprising:

a cell phone including a camera and a lens to provide images to a sensor including an array of pixels, the array of pixels including a plurality of columns of pixels, wherein some of the plurality of columns of pixels include a plurality of pixels and a column line coupled to an output of each of the plurality of pixels; and

a plurality of column amplifiers, wherein at least one of the plurality of column amplifiers is coupled to a single one of the column lines at a first column amplifier input and to a voltage reference at a second column amplifier input, wherein the at least one of the plurality of column amplifiers includes a first transistor having a first channel ratio and a first gate coupled to the single one of the column lines, and a second transistor having a second channel ratio that is greater than the first channel ratio, the second transistor including a second gate coupled to the voltage reference, and wherein some of the plurality of column amplifiers provide an output current I_out at an output determined by the formula;

I_out≈

V_d*(2*N)/(N+1)*(I_b/Vsat_2nd)

wherein V_d is a differential voltage appearing between the first column amplifier input and the second column amplifier input, N is a fraction determined by the second channel ratio and the first channel ratio, I_b is a total bias current of the column amplifier, and Vsat_2nd is a saturation voltage of the second transistor.

17. The system of claim 16, further including:

a memory for storing images received by the camera.

18. The system of claim 16, further including:

an input/output connection coupled to an antenna operable to email images received by the camera.

19. The system of claim 16, further including:

a keypad to user input including text to be superimposed on at least one image received by the camera.

20. The system of claim 16, wherein the sensor includes:

a complementary metal oxide sensor.

21. A system comprising:

a digital camera including a lens to provide images to a sensor including an array of pixels, the array of pixels including a plurality of columns of pixels, wherein some of the plurality of columns of pixels include a plurality of pixels and a column line coupled to an output of each of the plurality of pixels; and

a plurality of column amplifiers, wherein at least one of the plurality of column amplifiers is coupled to a single one of the column lines at a first column amplifier input and to a voltage reference at a second column amplifier input, wherein the at least one of the plurality of column amplifiers includes a first transistor having a first channel ratio and a first gate coupled to the single one of the column lines, and a second transistor having a second channel ratio that is greater than the first channel ratio, the second transistor including a second gate coupled to the voltage reference, and wherein some of the plurality of column amplifiers provide an output current I_out at an output determined by the formula;

I_out≈

V_d*(2*N)/(N+1)*(I_b/Vsat_2nd)

wherein V_d is a differential voltage appearing between the first column amplifier input and the second column amplifier input, N is a fraction determined by the second channel ratio and the first channel ratio, I_b is a total bias current of the column amplifier, and Vsat_2nd is a saturation voltage of the second transistor.

22. The system of claim 21, wherein the sensor includes:

a complementary metal oxide sensor.

23. A method comprising:

receiving an image at a lens of a digital camera;

providing the image to a pixel array; and

coupling a signal from the pixel array to at least one amplifier apparatus, wherein coupling the signal to the at least one amplifier includes;

receiving a first input signal at a first input of the amplification apparatus, the first input coupled to a first transistor having a first channel ratio;

receiving a second input signal at a second input of the amplification apparatus, the second input coupled to a second transistor having a second channel ratio that is approximately N times greater than the first channel ratio, wherein N is greater than or equal to two; and

amplifying the first and second input signals to provide an output signal at an output of the amplification apparatus, wherein the output signal has a gain bandwidth that is determined by approximately twice the value of N divided by N+1.

24. The method of claim 23, wherein amplifying the first and the second input signals includes:

providing the output signal having a slew rate that is approximately proportional to N.

25. The method of claim 23, wherein N has a value of about 5 to about 10.

26. The method of claim 23, wherein providing the output signal at the output coupled to the second transistor includes the amplifier providing an output current I_out at the output determined by the formula:

I_out≈

V_d*(2*N)/(N+1)*(I_b/Vsat_2nd)

wherein V_d is a differential voltage appearing between the first input and the second input, N is a fraction determined by the second channel ratio and the first channel ratio, I_b is a total bias current of the amplifier, and Vsat_2nd is a saturation voltage of the second transistor.

27. The method of claim 23, wherein providing the output signal includes:

providing a voltage to a sample and hold capacitor representing a difference between the first input signal and a reference voltage provided as the second input signal.

28. The method of claim 23, wherein receiving a second signal includes:

selecting a pixel from a plurality of pixels, each of the plurality of pixels having an output, and receiving the output of the selected pixel as the second signal.