Chopper-Stabilized Class AB Amplifier With Reduced Switch Resistance
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Solution Overview
Problem
The on-resistance of chopper switches in amplifiers can adversely affect circuit characteristics, particularly in applications requiring low noise at low frequencies.
Innovation Solution
A class AB amplifier design incorporating input and output chopper switch circuits synchronized with chopper clock signals, along with input and output amplifier circuits, to modulate and demodulate signals, thereby reducing the impact of chopper switch on-resistance on circuit characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If chopper switches are used in the amplifier, then low noise at low frequencies is achieved, but the on-resistance of the chopper switches adversely affects circuit characteristics
Solution Approach 1:
The amplifier is divided into multiple stages with separate chopper switch circuits at the input and output. Each chopper switch circuit is independently controlled by dedicated clock signals, allowing the noise reduction function to be segmented and distributed throughout the signal path rather than concentrated in a single location, thereby reducing the impact of individual switch on-resistances.
Solution Approach 2:
Modulator circuits and demodulator circuits are introduced as intermediary components between the chopper switches and the signal path. The modulator converts the input signal to a higher frequency before it passes through the chopper switches, and the demodulator converts it back afterward. This intermediary modulation process allows the signal to bypass the frequency-dependent on-resistance effects of the chopper switches.
2Object-affected harmful factors
If chopper switches are used for signal modulation, then noise reduction is improved, but the on-resistance introduces signal loss and distortion
Solution Approach 1:
The signal is pre-modulated to a higher frequency range before entering the chopper switch circuits. This preliminary frequency transformation allows the signal to be processed by the chopper switches in a frequency range where their on-resistance has less impact, thereby reducing signal loss and distortion while maintaining noise reduction benefits.
Solution Approach 2:
The operating frequency of the signal is dynamically changed through modulation before passing through the chopper switches. By transforming the signal frequency parameter, the interaction between the signal and the chopper switch on-resistance is altered, reducing the harmful effects of resistance-induced signal loss and distortion while preserving the noise filtering capability.
Data Source
AI summary
The class AB amplifier device includes an input chopper switch circuit that performs a chopping operation in synchronization with a first and second chopper clock signal, and outputs first and second modulated signals obtained by modulating the first and second differential input signals to a first and second node; an input amplifier circuit that receives the first and second modulated signals via the first and second nodes, and outputs a differential amplified signal obtained by amplifying the first and second modulated signals; an output chopper switch circuit that receives the differential amplified signal, performs a chopping operation in synchronization with the first and second chopper clock signals, and modulates the differential amplified signal to output a demodulated signal demodulated to the frequency band of the first and second differential input signals; and an output amplifier circuit that outputs a first output signal obtained by amplifying the demodulated signal.