Amplifier Feedback Circuit for Correlated Double Sampling Offset Compensation
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Solution Overview
Problem
In amplification circuits with stacked transistors, the use of AC coupling capacitors for correlated double sampling leads to poor offset voltage compensation and reduced performance due to capacitors being connected in series on the input signal path, which is not ideal for ensuring equal input voltages for P-type and N-type transistors.
Innovation Solution
The amplification circuit employs multiple feedback units and correlated double sampling units with capacitors and switch sets to control electrical connections, allowing for effective sampling and compensation of offset voltages without series connection of capacitors, thereby improving performance by ensuring proper voltage compensation for both types of transistors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If AC coupling capacitors are used for correlated double sampling, then offset voltage compensation is performed, but multiple capacitors become connected in series on the input signal path resulting in poor offset voltage compensation
Solution Approach 1:
The patent divides the single correlated double sampling function into two separate units: a first correlated double sampling unit for the first stacked transistor and a second correlated double sampling unit for the second stacked transistor. Each unit has its own capacitors and switches, eliminating the series connection problem while maintaining offset voltage compensation for both transistors independently.
Solution Approach 2:
The patent introduces separate feedback units (first feedback unit and second feedback unit) as intermediaries between the amplifier output and the respective correlated double sampling units. These feedback units provide independent feedback paths that avoid the series connection of capacitors while still enabling offset voltage compensation.
2Adaptability or versatility
If different input voltages are applied to stacked P-type and N-type transistors, then Class AB amplifier characteristics are achieved, but capacitor series connection reduces overall circuit performance
Solution Approach 1:
The patent applies different input voltages locally to each stacked transistor (first and second positive input voltages for P-type, first and second negative input voltages for N-type) through separate correlated double sampling units. This local customization enables Class AB characteristics while avoiding the performance degradation caused by series-connected capacitors.
Data Source
AI summary
The present application discloses an amplification circuit. The amplification circuit includes an amplifier, a feedback unit, a second feedback unit, a first correlated double sampling unit, and a second correlated double sampling unit. The amplifier has a first positive input terminal, a second positive input terminal, a first negative input terminal, a second negative input terminal, a positive output terminal, and a negative output terminal. First terminals of the first feedback unit and the second feedback unit are coupled to the positive output terminal. The first correlated double sampling unit is coupled to the first negative input terminal and a second terminal of the first feedback unit, and performs a sample operation and an output operation. The second correlated double sampling unit is coupled to the second negative input terminal and a second terminal of the second feedback unit, and performs the sample operation and the output operation.