Sub-Threshold MOS Biasing Circuit for Low-Noise Miniaturization
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Solution Overview
Problem
Existing biasing circuits face challenges in miniaturization due to the large size of resistors required for noise filtering, which hinder the reduction or elimination of noise in bias voltages, limiting the miniaturization of electronic circuits.
Innovation Solution
A voltage biasing circuit utilizing a MOS transistor, a voltage control circuit, and a capacitor, with a voltage buffer configured as a unity gain buffer amplifier, operates the MOS transistor in a sub-threshold range to achieve noise reduction with a smaller footprint, employing a current source and resistors to control the voltage and current flow effectively.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If an RC filtering circuit is used to eliminate noise in bias voltage, then noise reduction is achieved, but the circuit area increases due to large resistor size
Solution Approach 1:
The patent changes the operating parameter of the MOS transistor to operate in the sub-threshold region instead of the conventional linear or saturation region. This parameter change enables the MOS transistor to exhibit high resistance characteristics (several hundred kilo ohms to several mega ohms) while occupying minimal circuit area, thereby achieving noise filtering without requiring large physical resistors
Solution Approach 2:
The patent substitutes physical resistor components with an active MOS transistor device that electronically simulates high resistance through sub-threshold operation. This substitution replaces the mechanical/physical resistor structure with an electronically controlled device that achieves the same noise filtering function with dramatically reduced area
2Object-affected harmful factors
If large resistance value resistors are used for noise filtering, then noise elimination is effective, but miniaturization of the circuit is prevented
Solution Approach 1:
By changing the operating region parameter of the MOS transistor to sub-threshold mode, the device exhibits high resistance characteristics that enable effective noise filtering while maintaining a compact structure that supports circuit miniaturization
Solution Approach 2:
The MOS transistor performs multiple functions: it acts as a high-value resistor for noise filtering, serves as an active circuit element that can be integrated with other components, and enables miniaturization through its compact structure compared to physical resistors of equivalent resistance value
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 solution enables efficient noise filtering, reducing the area required for noise elimination by 95% compared to traditional RC circuits, while maintaining a high impedance to block current supply, thereby minimizing noise and phase noise deterioration in bias voltages.
Implementation Method 1
The voltage control circuit controls a voltage between a gate and a source of the MOS transistor to allow the MOS transistor to operate in a sub-threshold range
Implementation Method 2
The capacitor is connected to the MOS transistor
Implementation Method 3
The voltage buffer may an OPAMP that is configured as a unity gain buffer amplifier
Data Source
AI summary
A voltage biasing circuit includes a metal-oxide-semiconductor (MOS) transistor, a voltage control circuit controlling a voltage between a gate and a source of the MOS transistor to operate the MOS transistor in a sub-threshold range, and a capacitor connected to the MOS transistor. The voltage biasing circuit may further include a voltage buffer connected between the voltage control circuit and the MOS transistor.