OTA Chopper Amplifier Sampling Circuit for Spike Noise Reduction
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Solution Overview
Problem
Conventional chopper amplifiers suffer from spike noise due to clock feedthrough of switches, which increases chip size requirements for noise removal.
Innovation Solution
An amplifier design incorporating a signal polarity inversion circuit, an operational transconductance amplifier (OTA) circuit, and a sample-hold circuit with a sampling capacitor to reduce spike noise without increasing chip size, replacing the need for a low-pass filter.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If a low-pass filter is added to remove spike noise from clock feedthrough, then noise removal is improved, but chip size increases
Solution Approach 1:
The harmful clock feedthrough spike noise is extracted and removed from the signal path by the sample-hold circuit. The circuit separates the noise component from the useful signal by sampling only during specific time windows when the noise is absent, effectively taking out the noise without requiring additional filtering components that would increase chip size.
Solution Approach 2:
The sample-hold circuit employs periodic sampling action synchronized with the clock signal. By sampling the amplifier output at specific periodic intervals when the switching noise is minimal or absent, the circuit achieves noise rejection without requiring continuous filtering. This periodic sampling approach removes spike noise while maintaining compact implementation.
2Object-affected harmful factors
If the resistance and capacitance of the low-pass filter are increased to improve damping effect, then noise filtering is improved, but chip size increases
Solution Approach 1:
The traditional mechanical/electrical low-pass filter system is replaced with a temporal sampling system. Instead of using large R and C values to achieve damping and noise filtering, the invention uses time-domain sampling to achieve the same noise rejection effect. This substitution eliminates the need for large passive components while maintaining effective noise filtering.
3Power
If conventional chopper modulation is used to amplify small signals, then signal amplification is achieved, but spike noise is generated by clock feedthrough
Solution Approach 1:
The sample-hold circuit performs preliminary action by pre-synchronizing the sampling timing with the clock signal phases. By anticipating the arrival of clock feedthrough noise and sampling just before or during safe time windows, the circuit prevents noise contamination before it can corrupt the amplified signal. This preliminary timing coordination maintains signal amplification while avoiding spike noise generation.
Data Source
AI summary
An amplifier includes: a signal polarity inversion circuit which modulates an input signal and outputs a modulation signal; an amplifier circuit which is constituted from an operational transconductance amplifier (OTA) to amplify the modulation signal and output a current; and a sample-hold circuit having a sampling capacitor which is charged and discharged by selective sampling of the output current of the amplifier circuit and a holding capacitor to which the voltage of the sampling capacitor is transferred.