Fixed-Gain Instrumentation Amplifier With PGA-Aware Power Scaling
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Solution Overview
Problem
Conventional fixed gain amplifier (FGA) circuits face challenges in managing power dissipation and maintaining accurate gain settings when the programmable gain value changes, particularly in analog-to-digital conversion processes, where higher programmable gain values lead to increased power dissipation and output swing changes.
Innovation Solution
A circuit with selectively enabled current drive sources and variable resistors, where the resistances are scaled inversely with respect to the downstream programmable gain, and current drive sources are enabled proportionately, ensuring a fixed gain while controlling power dissipation and maintaining accurate gain settings.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If higher programmable gain values are used in the downstream amplifier, then the signal amplification capability is improved, but the power dissipation in the fixed gain amplifier increases
Solution Approach 1:
The patent implements dynamic adjustment of the fixed gain amplifier's operating parameters based on the downstream programmable gain value. The control circuit modifies the fixed gain amplifier's gain and output swing according to the detected PGA gain setting, allowing the system to adapt its power consumption characteristics to match the actual signal processing requirements rather than operating at fixed high power levels throughout
Solution Approach 2:
The patent changes the operating parameters (gain and output swing) of the fixed gain amplifier based on the downstream programmable gain value. When the PGA operates at higher gain settings, the FGA reduces its output swing and adjusts its gain accordingly, effectively changing its operational state to reduce power dissipation while maintaining the required overall signal amplification capability
2Adaptability or versatility
If the programmable gain value changes, then the adaptability to different signal sources is improved, but the gain setting accuracy deteriorates due to power dissipation variations
Solution Approach 1:
The patent employs a control circuit that detects the programmable gain value and uses this information to adjust the fixed gain amplifier's operating parameters. This feedback mechanism ensures that the FGA operates at optimal gain and output swing settings corresponding to each PGA configuration, maintaining gain setting accuracy across different operating conditions by continuously adapting to the system state
Solution Approach 2:
The control circuit preliminarily determines the appropriate fixed gain amplifier operating parameters based on the detected programmable gain value before the signal processing occurs. By pre-adjusting the FGA's gain and output swing according to the PGA setting, the system ensures accurate gain implementation from the outset rather than requiring correction during operation
3Adaptability or versatility
If the output swing is increased to handle higher gain settings, then the signal processing range is improved, but the power dissipation increases
Solution Approach 1:
The patent dynamically adjusts the output swing of the fixed gain amplifier based on the downstream programmable gain value. When the PGA operates at higher gain settings, the FGA reduces its output swing since less amplification is needed downstream, and vice versa. This dynamic adaptation allows the system to process signals across a wide range of gain settings while minimizing power dissipation at each operating point
Data Source
AI summary
An instrumentation amplifier includes first and second resistors for gain setting. The operational amplifiers within the instrumentation amplifier include selectively enabled current drive sources coupled to the amplifier output. The first and second resistors have variable resistances. A control circuit is configured to select the variable resistances of the first and second resistors to implement a fixed gain for the instrumentation amplifier and further selectively enable the current drive sources. The control circuit receives an indication of a downstream programmable gain (for example, from a downstream programmable gain amplifier). The variable resistances of the first and second resistors are selected to be scaled inversely with respect to the downstream programmable gain and the current drive sources are enabled proportionately with respect to the downstream programmable gain.