Dual-Path Chopper Amplifier with Interleaved Notch Filtering
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Chopper stabilized amplifiers with notch filters face stability issues at high bandwidth due to notch filter delay, which increases noise and reduces gain when the chopping frequency is increased to improve stability, leading to increased offset, drift, and input bias current.
Innovation Solution
A dual path chopper-stabilized amplifier design with two parallel chopping/notch-filtering paths, where each path is controlled by different clock signals, allowing the outputs of the switched capacitor notch filters to update a capacitance at four times the filter clock frequency, thereby improving stability without increasing the chopping frequency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If the chopping frequency is increased to improve amplifier stability, then stability is improved, but noise increases and gain reduces
Solution Approach 1:
The single chopping path is segmented into two parallel paths with different delay characteristics. Each path processes the same signal but with different timing, allowing the combined output to achieve stability without requiring high chopping frequency. The segmentation of the chopping operation into multiple phases with different clock signals enables stability improvement while avoiding the noise penalty associated with high-frequency chopping.
2Stability of the object's composition
If the chopping frequency is increased to improve amplifier stability, then stability is improved, but gain reduces
Solution Approach 1:
The amplification function is segmented across two parallel paths operating at lower effective frequencies. Each path contributes to the overall gain while the combined output achieves the stability that would otherwise require higher chopping frequency. This segmentation allows maintaining adequate gain levels while improving stability through the dual-path architecture.
3Stability of the object's composition
If the chopping frequency is increased to improve amplifier stability, then stability is improved, but offset increases
Solution Approach 1:
The offset correction function is segmented into two parallel chopping paths that operate with different clock phases. Each path handles offset correction independently, and their combined output achieves better offset performance than a single high-frequency path. The segmentation allows offset cancellation to occur at lower effective frequencies, reducing the offset penalties associated with high-frequency chopping.
4Stability of the object's composition
If the chopping frequency is increased to improve amplifier stability, then stability is improved, but drift increases
Solution Approach 1:
The drift compensation mechanism is segmented across two parallel paths with different operating frequencies. Each path independently compensates for drift in its respective signal path, and the combined output achieves superior drift performance. This segmentation enables drift cancellation without requiring the high chopping frequency that would otherwise be needed for stability, thereby reducing drift penalties.
5Stability of the object's composition
If the chopping frequency is increased to improve amplifier stability, then stability is improved, but input bias current increases
Solution Approach 1:
The input bias current management is segmented across two parallel paths operating at lower effective frequencies. Each path draws less bias current than a single high-frequency path would require, and their combined operation achieves the desired stability. This segmentation reduces the total input bias current while maintaining stability through the dual-path architecture.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This design enhances amplifier stability while preserving low offset and drift, reduces noise, and maintains low input bias current, even when the chopping frequency cannot be increased, effectively addressing the limitations of prior art chopper stabilized amplifiers.
Implementation Method 1
A first switched capacitor notch filter has an input coupled to an output of the first output chopper circuitry and performs an integrate and transfer function on a chopped output signal produced by the first output chopper circuitry
Implementation Method 2
Outputs of the first and second switched capacitor notch filters are combined to provide an amplifier output signal that updates a capacitance at four times the frequency of the filter clock signal
Data Source
AI summary
A dual path chopper-stabilized amplifier (100) includes first (11) and second (11A) chopping/notch-filtering paths, each including an input chopper (9,9A), a transconductance amplifier (2,2A), and a notch filter (15,15A). Chopping and notch filtering in the first path are controlled by first (CHOPCLK) and second (FILTERCLK) clock signals, respectively. Chopping and notch filtering in the second path are controlled by the second (FILTERCLK) and first (CHOPCLK) clock signals, respectively. Outputs of the first (15) and second (15A) switched capacitor notch filters are combined to provide an amplifier output signal (23A,B) that updates a capacitance (C4) at 4 times the frequency of the filter clock signal, to thereby improve amplifier stability without increasing clock frequency.