Amplifier Circuit Compensating Unit for Loop Gain and Linearity
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Solution Overview
Problem
Conventional amplifier circuits face limitations in increasing loop gain and system linearity due to constraints on the feedback factor and open-loop gain, which restrict the improvement of linearity and noise rejection.
Innovation Solution
The introduction of a compensating amplifier unit between the former stage amplifier unit and the output stage amplifier unit, comprising operational amplifiers, resistors, and capacitors, which increases the loop gain by amplifying the difference between the input and feedback signals and provides a zero point in the frequency domain for enhanced phase margin and stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the feedback factor β is increased to increase the loop gain A(s)β, then the loop gain increases and system linearity improves, but the close-loop gain decreases
Solution Approach 1:
The amplifier is divided into multiple stages: a first amplifier stage providing voltage gain, a second amplifier stage (compensating amplifier) providing additional gain and compensation, and an output stage. This segmentation allows the loop gain to be increased through cascaded stages rather than relying solely on feedback factor adjustment, thus improving linearity without sacrificing close-loop gain.
2Manufacturing precision
If the open-loop gain A(s) is increased by coupling the integrator circuit to the output stage amplifier unit to improve system linearity, then the loop gain increases, but the device complexity increases and stability issues arise
Solution Approach 1:
A compensating amplifier stage is introduced as an intermediary between the first amplifier stage and the output stage. This compensating amplifier includes a series compensation capacitor that provides phase compensation, allowing the system to achieve high loop gain for improved linearity while maintaining stability without requiring complex integrator circuits.
3Manufacturing precision
If the capacitor C1 of the integrator circuit or the resistance of feedback resistor Rf is decreased to increase the loop gain, then the loop gain increases, but system stability deteriorates and operational frequency range is limited
Solution Approach 1:
The compensating amplifier stage introduces a series compensation capacitor that changes the frequency-dependent parameters of the feedback network. By carefully selecting the compensation capacitor value, the phase margin is optimized across the operational frequency range, allowing high loop gain for improved linearity while maintaining system stability without being constrained by integrator circuit limitations.
Data Source
AI summary
An amplifier circuit includes a feedback loop; a former stage amplifier unit coupled to an input node of the amplifier circuit and the feedback loop for amplifying the difference between an input signal received from the input node and an output signal which comes back through the feedback loop, and outputting a first output signal; a compensating amplifier unit coupled to the former stage amplifier unit for amplifying the first output signal and outputting a second output signal; and an output stage amplifier unit coupled to the compensating amplifier unit and the feedback loop for outputting a third output signal according to the second output signal.