Operational Amplifier Noise Separation Using Dual Modulation
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Solution Overview
Problem
Conventional methods for reducing flicker noise in operational amplifiers, such as enlarging transistor area or using auto-zero mechanisms, are inefficient and increase chip power load or require additional components, while chopper methods require complex switch components and recovery time.
Innovation Solution
An amplifier with a built-in modulator system that separates noise signals into different frequency bands using two modulators, allowing for effective filtering of noise signals by modulating low-frequency flicker noise to a higher band, thereby enabling efficient noise reduction without increasing chip area or power load.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If the area of the transistor is enlarged to reduce flicker noise, then the flicker noise is reduced, but the chip area and power load increase
Solution Approach 1:
The patent changes the frequency parameter of the noise signal through modulation. By modulating the low-frequency flicker noise to a higher frequency band, the noise characteristics are transformed, allowing separation from the original signal band without requiring larger transistor area.
Solution Approach 2:
The patent introduces a frequency dimension transformation by using modulators to shift the noise signal from the baseband (low frequency) to a higher frequency band. This dimensional change in frequency space enables noise separation without spatial expansion of the transistor area.
2Object-affected harmful factors
If conventional chopper methods are used to modulate flicker noise, then noise modulation is achieved, but device complexity and recovery time increase
Solution Approach 1:
The patent merges the modulation function directly into the amplifier structure. The modulators are integrated with the amplifier stages, combining signal amplification and noise modulation functions in a unified structure, thereby reducing the need for separate complex switch components and control circuits.
Solution Approach 2:
The amplifier stages in the patent serve multiple functions: they amplify the desired signal while simultaneously acting as part of the modulation system for noise separation. This multi-functionality reduces overall device complexity compared to dedicated chopper switches with separate control logic.
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
The proposed solution effectively separates and filters out noise signals, improving the signal-to-noise ratio by utilizing two modulators to shift flicker noise to a higher band, where it can be easily filtered, thus enhancing the performance of operational amplifiers in ADC and DAC applications.
Implementation Method 1
a first modulator, coupled to the input stage, for modulating the first signal to generate a second signal corresponding to a second band
Data Source
AI summary
An amplifier includes: an input stage for receiving an input signal to generate a first signal corresponding to a first band; a first modulator coupled to the input stage for modulating the first signal to generate a second signal corresponding to a second band; an amplifier stage coupled to the first modulator for processing the second signal to generate a third signal, wherein the third signal includes a fourth signal corresponding to the second band and a first interference signal corresponding to the first band; and a second modulator coupled to the amplifier stage for modulating the third signal to generate a fifth signal corresponding to the first band and to generate a second interference signal corresponding to the second band.