Coded data generation or conversion – Phase or time of phase change
Reexamination Certificate
2000-03-21
2001-03-13
Young, Brian (Department: 2819)
Coded data generation or conversion
Phase or time of phase change
C341S120000, C327S095000, C327S096000
Reexamination Certificate
active
06201489
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention generally relates to differential and other amplifiers and, more particularly, to methods of reducing DC offset for low power applications.
2. Background Description
Power supply voltages continue to decrease as technology advances and as applications require lower voltages and longer battery life. DC offsets introduced by device mismatches are therefore becoming a larger percentage of the total power supply, thereby reducing the available dynamic range. Matching components on an integrated circuit is difficult and has not improved as rapidly as technology and power supply scaling. The subject of this invention is a circuit topology or architecture for DC offset cancellation.
SUMMARY OF THE INVENTION
The DC offset cancellation circuit according to the invention receives two input signals. A first one of the input signals is amplified by an amplifier, and the amplified output signal of the amplifier is tracked and held during a first clock phase. Simultaneously, during the first clock phase, the second one of the input signals is tracked and held. During the second clock phase succeeding the first clock phase, the stored second one of the input signals is amplified by the same amplifier that was used to amplify the first one of the input signals. The amplified and stored first one of the input signals and the amplified second one of the input signals are summed during the second clock phase to remove any DC offset. The summed signals are sampled and held during the second clock phase. The offset of the summer circuit can be canceled by sequential digital processing.
REFERENCES:
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patent: 5517141 (1996-05-01), Abdi et al.
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patent: 6084538 (2000-07-01), Kostelnik et al.
Bruns Sharon Von
Castellucci Gregg R.
Ohlson Kevin B.
International Business Machines - Corporation
McGuireWoods LLP
Nguyen John B
Shkurko, Esq. Eugene I.
Young Brian
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