Amplifier Gain Setting Using External Resistor Voltage Comparison
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Solution Overview
Problem
Traditional amplifier circuits rely on a single external resistor for gain setting, which can lead to inaccuracies and performance issues due to tolerance and temperature coefficient variations, limiting the flexibility and accuracy of gain settings.
Innovation Solution
The proposed solution involves using an external resistor to determine an internal gain setting by comparing the voltage across it to an on-chip reference, allowing a logic circuit to program the gain, thereby eliminating the need for high-accuracy external resistors and improving initial gain accuracy and drift without requiring changes to the amplifier's footprint.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a single external resistor is used to set the gain, then the amplifier circuit is simple and easy to manufacture, but the gain accuracy is limited by the resistor's tolerance and temperature coefficient
Solution Approach 1:
The patent introduces an on-chip resistor string as an intermediary element between the external resistor and the gain setting function. The external resistor's voltage is compared against the resistor string voltages to indirectly select the gain setting, rather than using the external resistor's resistance value directly in the gain equation. This mediator approach allows the external resistor to serve as a simple reference while the actual gain determination is performed by the precise on-chip resistor string.
Solution Approach 2:
The patent replaces the direct electrical relationship between the external resistor and gain setting with a voltage comparison mechanism. Instead of using the external resistor's resistance value directly in the gain calculation, the system converts the resistance setting into a voltage reference and uses comparator circuits to determine the appropriate gain setting based on voltage levels. This substitution transforms a precision-resistance-dependent system into a voltage-comparison-based system.
2Manufacturing precision
If a high-accuracy external resistor is used, then the gain accuracy improves, but the cost and availability of components are negatively impacted
Solution Approach 1:
The patent enables the use of inexpensive, readily available external resistors with standard tolerances (e.g., 1% or 5%) instead of requiring high-precision resistors. The external resistor serves only as a coarse reference element, while the fine gain accuracy is achieved through the on-chip resistor string and comparator logic. This approach makes the amplifier accessible to a broader range of applications where cost and component availability are critical factors.
Solution Approach 2:
The on-chip resistor string acts as an intermediary that bridges the gap between the low-precision external resistor and the high-accuracy gain requirement. By comparing the external resistor's voltage against the precisely manufactured on-chip resistor string, the system achieves high gain accuracy without requiring the external resistor to be high-precision, thus using inexpensive, readily available components.
3Reliability
If the external resistor's tolerance varies, then the gain drift increases, but using a precision resistor increases cost
Solution Approach 1:
The on-chip resistor string serves as a stable intermediary reference that is manufactured with tight tolerances and matched temperature coefficients to the internal amplifier components. By comparing the external resistor's voltage against this stable on-chip reference, the system achieves gain stability without requiring the external resistor to be high-precision or temperature-stable, thus reducing component cost while maintaining reliability.
Solution Approach 2:
The patent implements a feedback mechanism where the voltage across the external resistor is continuously compared against the on-chip resistor string voltages. The comparator circuits detect any drift or variation in the external resistor's voltage and use this information to select or adjust the appropriate gain setting, effectively compensating for external resistor variations and maintaining gain stability.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach enhances gain accuracy and flexibility while maintaining compatibility with standard amplifier footprints, allowing for substantial improvements in existing systems with minimal changes to the bill of materials.
Implementation Method 1
a voltage across the external resistor can be compared to an on-chip reference
Data Source
AI summary
Techniques for setting a gain of an amplifier circuit in which the external resistor of the amplifier circuit is used to determine an internal gain setting to select. A voltage across the external resistor can be compared to an on-chip reference, and then used to program the desired gain. The techniques can mitigate or eliminate the need for a high-accuracy external resistor and can allow substantial improvements in initial gain accuracy and gain drift for existing boards and/or systems with only a bill of material change.