Programmable Gain Amplifier Gain Blending for Trim Accuracy
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Solution Overview
Problem
Conventional programmable gain amplifiers face significant gain errors due to resistor mismatches caused by processing and operating condition differences, which are costly to correct using continuous laser trimming and can be inaccurate due to manufacturing stresses.
Innovation Solution
A digital means for trimming and adjusting the gain in programmable gain amplifier circuits, using a gain adjust circuit and a gain select circuit coupled to an operational amplifier, with digital control signals to boost or cut the gain, allowing for accurate signal amplification and in-circuit calibration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If continuous laser trimming is used to correct gain errors, then gain accuracy is improved, but manufacturing cost increases
Solution Approach 1:
The patent replaces the mechanical laser trimming process with a digital correction system. A digital-to-analog converter (DAC) generates correction signals based on stored trim values, which are then applied to adjust the amplifier gain electronically. This substitution eliminates the need for physical laser trimming while achieving comparable or superior gain accuracy, thereby reducing manufacturing costs and complexity.
Solution Approach 2:
The patent performs gain trimming measurements and stores correction values in a lookup table during the manufacturing process, before the actual product deployment. These pre-calculated trim values are then used during operation to correct gain errors without requiring additional real-time adjustments. This preliminary action eliminates the need for costly post-manufacturing laser trimming while ensuring accurate gain performance.
2Measurement precision
If laser trimming is used to correct gain errors, then gain accuracy is improved, but manufacturing complexity and stress increase
Solution Approach 1:
The patent replaces the mechanical laser trimming process with a digital correction system. A digital-to-analog converter (DAC) generates correction signals based on stored trim values, which are then applied to adjust the amplifier gain electronically. This substitution eliminates the need for physical laser trimming while achieving comparable or superior gain accuracy, thereby reducing manufacturing complexity and stress.
3Adaptability or versatility
If resistor values are changed to adjust gain, then gain scaling is achieved, but gain errors due to resistor mismatches increase
Solution Approach 1:
The patent implements a feedback mechanism where the actual gain of the amplifier is measured and compared against the desired gain value. The difference (error) is then used to generate correction signals that adjust the amplifier gain back to the target value. This closed-loop feedback system compensates for resistor mismatches and other variations, maintaining high gain accuracy across different gain scaling settings.
Solution Approach 2:
The patent changes the operating parameters of the amplifier by applying correction voltages or currents generated by a DAC system. Instead of physically changing resistor values, the system adjusts the electrical parameters (voltage/current) to compensate for gain errors. This allows gain scaling to be achieved while maintaining accuracy through digital parameter adjustment rather than physical component changes.
Data Source
AI summary
A programmable gain amplifier (PGA) circuit includes a gain adjust circuit and a gain select circuit that are both coupled to an output of an amplifier. The gain select circuit completes feedback to the amplifier while the gain adjust circuit is arranged to boost or cut the gain of the gain selection circuit. The gain adjust circuit can be arranged as a trim adjustment to the overall gain of the PGA circuit, where a different trim adjustment can be mapped to each gain setting such as from a look-up table. In other example implementations, the PGA circuit can periodically switch between multiple gain settings using a modulation scheme such that the overall gain is blended between the various gain settings according to a duty cycle, pulse-width, or delta-sigma modulation, with a time averaging effect on the overall gain of the PGA circuit.