Resistor-Ratio Amplifier Circuit for Low DC Offset Gain Control
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Solution Overview
Problem
Conventional semiconductor integrated circuits face errors in gain and DC offset voltage due to variations in the level shift operation, requiring a reduction in circuit size and power consumption while maintaining signal amplification and level shifting functionality.
Innovation Solution
An amplifier circuit design featuring a specific resistor configuration and operational amplifier setup, where the ratio of resistances between series-connected resistors ensures accurate level shifting and amplification with reduced operational amplifiers, minimizing DC offset and noise.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional level shift circuit with operational amplifier and resistors is used to shift DC level between different power supply voltages, then the signal can be level-shifted to match different power supply levels, but gain errors and DC offset voltage occur due to variations in level shift operation
Solution Approach 1:
The patent combines the level shift function and amplification function into a single operational amplifier circuit. The level shift is achieved by applying the input signal to the non-inverting terminal and using the inverting terminal for feedback, eliminating the need for a separate level shift circuit. This integration reduces the number of components and minimizes sources of error.
Solution Approach 2:
The patent employs negative feedback by connecting the output terminal to the inverting terminal through a feedback resistor. This feedback mechanism stabilizes the gain and reduces sensitivity to component variations, thereby improving gain accuracy and reducing DC offset voltage errors.
2Productivity
If separate level shift circuit and output-associated circuit are used, then level shifting and amplification can be performed, but circuit size and power consumption increase
Solution Approach 1:
The patent merges the level shift circuit and output-associated circuit into a single integrated circuit block. The operational amplifier simultaneously performs both level shifting (by referencing the input signal at the non-inverting terminal) and amplification (through the feedback network), eliminating the need for separate circuits and reducing overall circuit area.
Solution Approach 2:
The operational amplifier in the patent serves multiple functions: it acts as both a level shifter and an amplifier. By configuring the non-inverting terminal to receive the input signal and using the inverting terminal for feedback, the same circuit element accomplishes both tasks that would traditionally require separate dedicated circuits.
3Reliability
If conventional level shift circuit with multiple resistors and operational amplifiers is used, then level shifting can be achieved, but power consumption increases
Solution Approach 1:
The patent reduces power consumption by combining multiple functional blocks into a single operational amplifier circuit. Instead of powering separate level shift and output circuits, the integrated design requires only one operational amplifier, directly reducing the total power consumption while maintaining level shifting accuracy through proper feedback configuration.
4Ease of operation
If conventional amplifier circuit is used for mute operation, then signal can be blocked, but noise and DC offset voltage are generated
Solution Approach 1:
The negative feedback configuration stabilizes the operational amplifier during mute operation, preventing the generation of noise and DC offset voltage that would occur in conventional circuits. The feedback mechanism ensures that the output remains stable and controlled even when the signal path is interrupted.
Data Source
AI summary
An amplifier circuit that is less likely to cause an error in a gain and a DC offset voltage and is suitable for reducing a size and power consumption is offered. A first resistor and a second resistor are connected in series between an input terminal and an output terminal. A third resistor and a fourth resistor are connected in series between a VREFL terminal and a VREFH terminal. A ratio of a resistance of the first resistor to a resistance of the second resistor is equal to a ratio of a resistance of the third resistor to a resistance of the fourth resistor. A voltage at a connecting node between the first resistor and the second resistor is applied to a first differential input terminal (−) of an operational amplifier, while either a voltage at a connecting node between the third resistor and the fourth resistor or VREFH is selectively applied to a second differential input terminal (+) of the operational amplifier. An output of the operational amplifier is outputted through the output terminal as well as being applied to the first differential input terminal through the second resistor that serves as a feedback resistor.