Auto-Zero Amplifier Switching for Continuous Drift Compensation
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Solution Overview
Problem
Existing auto-zero amplifier circuits face issues with periodic non-operation phases and inability to compensate for temperature drift, leading to offset voltage problems, and require multiple amplifiers to mitigate these issues, resulting in increased circuit complexity.
Innovation Solution
A single OP amplifier circuit with a differential pair of transistors whose threshold voltages cause offset voltage, alternately switched to superimpose positive and negative offset voltages on the output, which are then filtered out using a low-pass filter to produce an accurate output voltage, allowing for continuous operation and temperature drift compensation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If periodic switching between compensation phase and operation phase is implemented, then offset voltage is eliminated, but the amplifier has periods of non-operation and cannot compensate for temperature drift
Solution Approach 1:
The patent implements periodic switching between first and second connection states of the switches, causing the differential pair transistors to alternately connect to different input terminals. This periodic action superimposes alternating positive and negative offset voltages on the output, which are then filtered by the low-pass filter to eliminate offset voltage while maintaining continuous operation.
Solution Approach 2:
The patent changes the connection state parameters of the switches periodically, transitioning between first and second connection states. This parameter change enables the differential pair transistors to alternately connect to different input terminals, generating alternating offset voltages that cancel each other out through the low-pass filter, thereby eliminating offset voltage while maintaining continuous operation.
2Productivity
If two auto-zero amplifiers are prepared for alternating compensation and normal operation, then continuous operation is achieved, but circuit scale increases
Solution Approach 1:
The patent merges the compensation function and normal operation function into a single auto-zero amplifier circuit. By periodically switching the connection state of the switches, the same amplifier performs both offset compensation and signal amplification continuously, eliminating the need for separate amplifiers and reducing circuit scale.
Solution Approach 2:
The single auto-zero amplifier circuit is designed to perform multiple functions: it continuously eliminates offset voltage through periodic switching while simultaneously performing signal amplification. The differential pair transistors and switches are configured to enable the same circuit to handle both compensation and operation tasks, achieving multi-functionality and reducing the number of components required.
3Productivity
If compensation is performed only at power supply turning-on, then continuous operation is maintained, but temperature drift compensation becomes impossible
Solution Approach 1:
The patent implements continuous offset voltage elimination by periodically switching the connection state of the switches throughout operation. This continuous action ensures that offset voltage is constantly compensated, including temperature drift effects, while maintaining uninterrupted signal amplification, thereby achieving both continuous operation and temperature drift compensation.
Data Source
AI summary
In aspects of the invention, at normal operation, an operational amplifier circuit has feedback applied from the output thereof to the input thereof so that currents equal to each other flow in differential pair transistors, respectively. While, in order that currents equal to each other may flow in the differential pair transistors, respectively, for compensating the difference in threshold voltages in the differential pair transistors, a voltage lower by a certain voltage difference than the voltage applied to the gate terminal of the transistor must be applied to the gate terminal of the transistor. From this, the switching of switches, when a virtual short circuit occurs, can make the output voltage of the operational amplifier circuit become a signal in which positive and negative rectangular ripples, with the values thereof being proportional to the value of the certain voltage difference, are superimposed on a true value.