Amplifier Circuit Offset Trimming Without Extra Compensation Stages
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Solution Overview
Problem
Conventional operational amplifiers require additional circuits for offset compensation, which introduce delays due to stray capacitance and necessitate extra components like resistors and current sources.
Innovation Solution
An amplifier circuit design using a pair of transistors with commonly connected gates, employing adjustable resistors connected between the gates and drains, allows for offset adjustment without additional operational amplifiers, thereby suppressing stray capacitance and eliminating the need for dedicated current sources.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If additional circuits are provided for offset compensation, then offset adjustment capability is improved, but stray capacitance increases causing operational delay
Solution Approach 1:
The patent extracts the offset compensation function from a separate additional operational amplifier circuit and integrates it directly into the existing amplifier circuit through resistors connected to the gates of the transistors. This eliminates the need for separate compensation circuits while maintaining offset adjustment capability, thereby reducing stray capacitance and operational delay.
Solution Approach 2:
The patent merges the offset compensation function with the main amplifier circuit by connecting resistors directly to the gates of the transistors. This consolidation integrates multiple functions into a single circuit structure, reducing the total number of components and minimizing stray capacitance effects.
2Measurement precision
If additional operational amplifier circuits are used for offset compensation, then offset adjustment capability is improved, but device complexity increases
Solution Approach 1:
The patent extracts only the essential offset compensation elements (resistors connected to transistor gates) from a complete additional operational amplifier circuit. This selective extraction provides offset adjustment capability while avoiding the complexity of full operational amplifier implementations.
Solution Approach 2:
The resistors connected to the transistor gates serve multiple functions: they provide offset compensation and simultaneously act as part of the biasing network. This multi-functionality reduces the need for separate dedicated components, simplifying the overall circuit structure.
Data Source
AI summary
An amplifier circuit includes a first transistor, through which a first input current is made to flow between the drain and the source; a second transistor, through which a second input current is made to flow between the drain and the source; a first-1 current source, which supplies a predetermined current to the gate of the first transistor; a first-2 current source, which supplies a predetermined current to the gate of the second transistor; a pair of adjustable resistors, which are connected in series between the gate of the first transistor and the gate of the second transistor; a connecting path, which connects a connection point of the pair of adjustable resistors to the drain of the first transistor; and a second current source, which supplies a current to the drain of the second transistor.