Semiconductor Device Gain Switching Resistor Network
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Solution Overview
Problem
Existing inverter control circuits face challenges in amplifying signals with high precision while removing noise, particularly due to the influence of on-resistance errors from analog switches and variations in common mode rejection ratio (CMRR) caused by gain fluctuations.
Innovation Solution
A semiconductor device is designed to set gain switching resistors on the inverting input terminal and offset switching resistors on the non-inverting input terminal of an operational amplifier, substantially removing analog switches from the current path, allowing for precise amplification and noise reduction without affecting the CMRR.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If analog switches are used in the current path for gain switching, then gain adjustment is enabled, but on-resistance errors cause amplification precision degradation
Solution Approach 1:
The patent extracts and removes the analog switches from the current path of the operational amplifier. Gain switching is achieved by switching the connection of resistors to the input terminal rather than placing switches directly in the signal current path, thereby eliminating on-resistance errors while preserving gain adjustment capability
Solution Approach 2:
The patent introduces resistors as intermediary elements that are switched via analog switches positioned away from the critical current path. The switches control which resistors are connected to the input terminal, enabling gain adjustment without the switch on-resistance directly affecting the amplification precision
2Adaptability or versatility
If gain is varied in existing amplifier circuits, then adaptability is improved, but common mode rejection ratio (CMRR) is degraded and varies with gain
Solution Approach 1:
The patent segments the amplifier circuit into distinct functional portions: a fixed-gain operational amplifier section and a separate resistor switching network. This segmentation allows the op amp to maintain its optimal operating conditions and fixed gain characteristics, while the resistor network provides overall gain control, thereby maintaining stable CMRR across different gain settings
Solution Approach 2:
The patent uses multiple resistors with different resistance values that are selectively connected to create different gain settings. Instead of varying the op amp gain directly, the circuit copies the gain control function through resistor selection, allowing the op amp to operate at a fixed, optimal point with stable CMRR while achieving gain variability through the resistor network
Data Source
AI summary
A semiconductor device includes first and second resistor groups, first and second switch groups, a register, and an amplifier. The first resistor group includes plural first resistors connected in series between a first terminal and an output of the amplifier. The first switch group includes plural first switches. Each of the first switches is connected between a corresponding one of the connection point between the first resistors and the inverting input terminal of the amplifier. The second resistor group includes plural second resistors connected in series between a second terminal of the amplifier and a reference voltage source. The second switch group includes plural second switches. Each of the second switches is connected between a corresponding one of the connection point between the second resistors and a positive input terminal of the amplifier. The register selects each of first and second switches.