Differential Amplifier Offset Adjustment Without Gain Loss
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Solution Overview
Problem
Conventional differential amplifier circuits face the challenge of reducing offset voltage without affecting the amplification gain, as the offset voltage adjustment circuit modifies the resistances in the current paths of the input transistors.
Innovation Solution
The proposed differential amplifier circuit connects an offset voltage adjustment circuit directly to the gates of the input transistors, using variable resistance circuits or current sources with fuses to adjust the gate voltage without altering the current path resistances, thereby reducing offset voltage without impacting amplification gain.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the offset voltage adjustment circuit is provided in the current paths of the input transistors to adjust resistances, then the offset voltage can be reduced, but the amplification gain is affected
Solution Approach 1:
The patent segments the offset voltage adjustment function from the main signal amplification path by providing a separate adjustment circuit that does not interfere with the current paths of the input transistors. This allows independent optimization of offset voltage correction without compromising amplification gain stability.
Solution Approach 2:
The patent introduces an intermediary mechanism (offset voltage adjustment circuit with fuse-based resistance control) that corrects offset voltage through a separate pathway. This intermediary approach allows offset adjustment without directly modifying the main signal current paths, thus preserving amplification gain.
2Measurement precision
If fuses are cut to adjust resistances in the offset voltage adjustment circuit, then the offset voltage is reduced, but the current path resistances of input transistors are changed
Solution Approach 1:
The patent separates the offset adjustment resistance from the signal path resistance by placing the adjustment circuit in a parallel or separate configuration. This segmentation ensures that fuse cutting for offset adjustment does not alter the resistance values in the main signal current paths of the input transistors.
Solution Approach 2:
The patent applies local quality change by providing different resistance characteristics in different parts of the circuit: the offset adjustment circuit has variable resistance (controlled by fuse cutting) while the main signal path maintains fixed, precise resistance values. This localized differentiation allows independent optimization of each function.
Data Source
AI summary
A differential amplifier circuit includes a first input transistor that receives a signal supplied from the first input terminal via a gate thereof, a second input transistor that receives a signal supplied from the second input terminal via a gate thereof, and an offset voltage adjustment circuit that is connected to at least one between the first input terminal and the gate of the first input transistor and between the second input terminal and the gate of the second input transistor.