Chopper Amplifier Offset Compensation With Ripple Reduction Loop
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Solution Overview
Problem
Electrical devices with amplifiers face challenges in compensating for signal variances such as magnitude and frequency variations without introducing undesirable qualities, particularly in reducing amplifier offsets and ripples in the output signals.
Innovation Solution
A ripple reduction loop system comprising a modulating chopper, null amplifier, demodulating chopper, integrator, and attenuator, which processes and compensates differential input signals to reduce amplifier offsets and ripples, including the use of filters and control signals to manage frequency and amplitude adjustments.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If amplifier offset compensation is implemented using conventional methods, then the offset is reduced, but ripple is introduced in the output signal
Solution Approach 1:
The compensation signal generation is divided into multiple stages: modulation stage (chopper 140), amplification stage (null amplifier 145), demodulation stage (chopper 150), integration stage (integrator 155), and attenuation stage (attenuator 160). Each stage processes the signal separately, allowing offset compensation while filtering out ripple through the integration and attenuation operations.
Solution Approach 2:
An integrator 155 is introduced as an intermediary component between the demodulating chopper 150 and the attenuator 160. The integrator processes the demodulated compensation signal and inherently filters high-frequency ripple components, allowing the system to achieve both offset compensation and ripple reduction simultaneously.
2Measurement precision
If offset compensation circuits are added to reduce amplifier offset, then measurement precision is improved, but device complexity increases
Solution Approach 1:
The ripple reduction loop 125 serves multiple functions simultaneously: it generates offset compensation signals, filters ripple through integration, attenuates the compensation signal to appropriate levels, and feeds it back to the main amplifier 102. This multi-functional approach consolidates what would otherwise require separate circuits into a single integrated system.
Solution Approach 2:
The system employs a feedback mechanism where the output of the main amplifier 102 is fed back through the ripple reduction loop 125, which processes the signal to extract offset components, generate compensation signals, and feed them back to cancel the original offset. This closed-loop feedback approach achieves precise offset compensation without requiring complex open-loop correction circuits.
3Measurement precision
If the compensation signal amplitude is increased to better compensate for offset, then offset reduction is improved, but ripple amplitude increases
Solution Approach 1:
The integrator 155 intentionally generates a compensation signal with amplitude that may exceed the required level (excessive action), and then the attenuator 160 reduces it to the appropriate level. This two-step process allows the system to first ensure sufficient offset compensation capability, then precisely control the final amplitude to minimize ripple while maintaining effective offset cancellation.
Solution Approach 2:
The system dynamically adjusts the amplitude parameter of the compensation signal through the integrator 155 and attenuator 160. The integrator increases the amplitude to ensure adequate compensation, while the attenuator subsequently reduces it to the optimal level, transforming the amplitude parameter through controlled changes to achieve both effective offset cancellation and minimal ripple.
Data Source
AI summary
An electrical circuit comprising a modulating chopper configured to receive a differential input signal at a first frequency and modulate the differential input signal to a second frequency to form a modulated differential signal, a null amplifier coupled to the modulating chopper and configured to amplify the modulated differential signal to form an amplifier output, wherein amplifying the modulated differential signal causes a ripple in the amplifier output, a demodulating chopper coupled to the null amplifier and configured to demodulate the amplifier output to form a demodulated differential signal having a first portion at the first frequency and a second portion at a third frequency, an integrator coupled to the demodulating chopper and configured to integrate the demodulated differential signal to form an integrated differential signal, and an attenuator coupled to the integrator and configured to attenuate the integrated differential signal to compensate for at least part of the ripple.