Sharing operational amplifier between two stages of pipelined ADC and/or two channels of signal processing circuitry
First Claim
1. An imager comprising:
- a pixel array;
sample and hold circuitry coupled to receive analog signals from pixels within the array;
an amplification circuit for amplifying the analog signals; and
a pipelined analog-to-digital converter connected to receive and convert the amplified analog signals to digital signals, said converter comprising;
an amplifier,first and second pipeline stages adapted to be switchably connected to the amplifier in response to first and second clock signals,a discharge circuit adapted to cause a discharge operation to occur at an input of the amplifier in response to a reset pulse; and
a clock generator, said clock generator generating first and second clock signals and a plurality of reset pulses, the first and second clock signals being generated such that they are non-overlapping, said clock generator applying the first and second clock signals and the reset pulses to the pipeline stages and the discharge circuit to change the connections between the pipeline stages, discharge circuit and the amplifier.
2 Assignments
0 Petitions
Accused Products
Abstract
A mechanism for discharging parasitic capacitance at an input of an operational amplifier, which is shared between two stages of a pipelined analog-to-digital converter and/or two channels of signal processing circuitry, before the amplifier configuration of the stages/channels is switched. The discharging act occurs when a short reset pulse is generated between two clock phases. The short reset pulse is applied to a switch connected to the operational amplifier input. When the reset pulse closes the switch, a discharge path is created and any parasitic capacitance at the operational amplifier input is discharged through the path. The discharging of the parasitic capacitance substantially mitigates the memory effect and the problems associated with the memory effect.
22 Citations
20 Claims
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1. An imager comprising:
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a pixel array; sample and hold circuitry coupled to receive analog signals from pixels within the array; an amplification circuit for amplifying the analog signals; and a pipelined analog-to-digital converter connected to receive and convert the amplified analog signals to digital signals, said converter comprising; an amplifier, first and second pipeline stages adapted to be switchably connected to the amplifier in response to first and second clock signals, a discharge circuit adapted to cause a discharge operation to occur at an input of the amplifier in response to a reset pulse; and a clock generator, said clock generator generating first and second clock signals and a plurality of reset pulses, the first and second clock signals being generated such that they are non-overlapping, said clock generator applying the first and second clock signals and the reset pulses to the pipeline stages and the discharge circuit to change the connections between the pipeline stages, discharge circuit and the amplifier. - View Dependent Claims (2, 3, 4, 5, 6, 7)
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8. An imager comprising:
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a pixel array; and a readout circuit comprising; first and second circuits coupled to receive analog signals from pixels within the array, an amplifier adapted to be switchably connected between the first and second circuits, and a discharge circuit adapted to be switchably connected to an input of the amplifier, the discharge circuit causing a discharge operation to occur at an input of the amplifier during a period in which the connections between the first and second circuits and the amplifier switch. - View Dependent Claims (9, 10, 11, 12, 13, 14, 15, 16, 17)
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- 18. A method of operating signal processing circuitry comprising two channels sharing an amplifier, said method comprises performing a first discharge operation at the amplifier during a first period in which portions of the first and second channels change operations.
Specification