Amplifier Circuit Offset Adjustment Using Gate Resistor Balancing
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Solution Overview
Problem
Conventional operational amplifiers require additional circuits and suffer from delays due to stray capacitance when adjusting offset compensation, necessitating an additional current source and resistors for offset compensation.
Innovation Solution
An amplifier circuit design that utilizes a pair of transistors with commonly connected gates, employing adjustable resistors to adjust offset voltages without needing an additional operational amplifier or current source, and suppresses stray capacitance by using a cascode connection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If additional circuits are used for offset compensation, then offset adjustment capability is improved, but device complexity increases
Solution Approach 1:
The patent combines the offset compensation function with the existing input structure by using resistors connected to the gates of the differential pair transistors. This merging approach allows offset adjustment without adding separate compensation circuits, thereby improving offset adjustment capability while avoiding increased device complexity.
Solution Approach 2:
The resistors Rt1 and Rt2 serve dual purposes: they provide offset compensation functionality while also being part of the input structure. This multi-functionality eliminates the need for dedicated compensation circuits, achieving precise offset adjustment without increasing overall circuit complexity.
2Measurement precision
If additional circuits are used for offset compensation, then offset adjustment capability is improved, but stray capacitance increases
Solution Approach 1:
By merging the offset compensation function into the existing input structure using minimal components (resistors Rt1 and Rt2), the patent achieves offset adjustment capability while minimizing the addition of capacitive elements. This approach provides precise offset control without significantly increasing stray capacitance.
3Measurement precision
If additional current sources are used for offset compensation, then offset adjustment capability is improved, but device complexity increases
Solution Approach 1:
The patent merges the offset compensation function with the existing bias current structure, using the same current sources that already power the amplifier. This eliminates the need for additional dedicated current sources for compensation, achieving precise offset adjustment while avoiding increased device complexity.
Solution Approach 2:
The existing bias current sources serve multiple functions: they power the main amplifier operation and simultaneously enable offset compensation through the resistive network. This multi-functionality removes the need for separate compensation current sources, maintaining simplicity while achieving precise offset control.
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. A current from the first-1 current source is supplied to the drain of the first transistor via one of the pair of adjustable resistors, and a current from the first-2 current source is supplied to the drain of the first transistor via the second adjustable resistor. By relatively adjusting resistance values of the first adjustable resistor and the second adjustable resistor, offsets of gate voltages of the first transistor and the second transistor can be adjusted.