Gain-Boosted ADC Driver Circuit for Low Harmonic Distortion
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Solution Overview
Problem
Precision ADCs experience significant distortion due to highly dynamic and non-linear output currents from drivers, leading to information loss and altered signal shapes, particularly in high-resolution conversions.
Innovation Solution
A driver design incorporating voltage followers, gain-boost amplifiers, compensation circuits, and cross-capacitor compensation circuits to stabilize current flow and minimize harmonic distortions, ensuring consistent charge/discharge of sampling capacitors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a precision ADC uses a large sampling capacitor to reduce noise, then measurement precision is improved, but the driver produces large dynamic and non-linear current causing distortions
Solution Approach 1:
The patent introduces a driver circuit as an intermediary between the signal source and the precision ADC. This driver includes a voltage follower stage with gain-boosting that acts as a mediator to buffer the ADC's switching transitions, isolating the signal source from the large dynamic currents required by the sampling capacitor while maintaining signal integrity.
Solution Approach 2:
The patent implements feedback mechanisms within the driver circuit, specifically using the gain-boosted voltage follower configuration where the output is fed back to the input through a high-gain amplifier. This feedback stabilizes the output impedance and reduces distortions by continuously adjusting the driver output to match the ideal voltage source behavior despite the capacitive load variations.
2Productivity
If the driver supplies large dynamic current to charge/discharge the sampling capacitor rapidly, then productivity is improved, but total harmonic distortion increases to approximately −109 dB
Solution Approach 1:
The patent employs dynamic circuit elements including the voltage follower with gain-boosting that can rapidly adjust its output characteristics. The driver circuit is designed to dynamically respond to the switching demands of the ADC sampling capacitor, adjusting its drive capability in real-time to maintain low distortion across varying sampling rates and signal conditions.
Solution Approach 2:
The patent changes key circuit parameters through the gain-boosted voltage follower configuration, transforming the driver's output impedance and current driving capability. By adjusting the gain parameter of the follower stage, the circuit can optimize the balance between fast charging/discharging capability and distortion reduction, allowing high productivity while maintaining signal fidelity.
Data Source
AI summary
A driver includes an inverting amplifier stage and a non-inverting amplifier stage. The inverting amplifier stage includes an inverting amplifier input and an inverting amplifier output. The inverting amplifier stage includes a first voltage follower which includes a first voltage follower input coupled to the inverting amplifier input and a first voltage follower output coupled to the inverting amplifier output. The inverting amplifier stage includes a first gain-boost amplifier coupled to the first voltage follower. The non-inverting amplifier stage includes a non-inverting amplifier input and a non-inverting amplifier output. The non-inverting amplifier stage includes a second voltage follower which includes a second voltage follower input coupled to the non-inverting amplifier input and a second voltage follower output coupled to the non-inverting amplifier output. The non-inverting amplifier stage includes a second gain-boost amplifier coupled to the second voltage follower.