MOS Amplifier Biasing Outside Saturation for Flicker Noise Reduction
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Solution Overview
Problem
MOS transistors used as buffers or amplifiers face challenges in reducing 1/f flicker noise, which affects their performance in various applications.
Innovation Solution
A bias circuit is coupled to the MOS transistor to maintain it outside of saturation, using either a fixed or adaptive bias to set the source-drain voltage, thereby reducing noise. This bias circuit can be configured to track changes in environmental conditions and process variations, ensuring the MOS transistor operates effectively without entering saturation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If a MOS transistor is maintained in saturation to operate as a buffer or amplifier, then its amplification capability is improved, but 1/f flicker noise increases
Solution Approach 1:
The patent changes the operating region parameter of the MOS transistor from saturation to non-saturation (linear/triode) region by adjusting the drain-source voltage VDS to be less than VDSAT. This parameter change allows the transistor to function as a buffer or amplifier while operating in a region that generates less 1/f flicker noise, thus resolving the contradiction between amplification capability and noise generation.
2Object-generated harmful factors
If a bias circuit is added to maintain the MOS transistor outside saturation, then noise is reduced, but device complexity increases
Solution Approach 1:
The bias circuit is designed to automatically maintain the MOS transistor in the non-saturation region without requiring external control or monitoring. The circuit self-adjusts the bias conditions to keep VDS < VDSAT, enabling noise reduction while minimizing the need for additional complex control mechanisms.
Solution Approach 2:
The bias circuit dynamically adapts to environmental changes and process variations through adaptive biasing mechanisms. This allows the circuit to maintain optimal operating conditions (non-saturation region) under varying conditions, reducing noise while keeping the complexity manageable through intelligent adaptation rather than rigid fixed-bias design.
Data Source
AI summary
There is provided a device that includes a MOS transistor and a bias circuit coupled to the MOS transistor. The bias circuit is configured to bias the MOS transistor thereby maintaining the MOS transistor outside of saturation. The MOS transistor is configured to operate as a buffer or an amplifier, while being outside of saturation.