CMOS Switch Filter Circuit for Noise Removal in Small Signal Paths
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing imaging devices face challenges in reducing noise while maintaining a compact circuit scale, as increasing the size of resistor elements to achieve effective noise removal leads to larger circuit sizes.
Innovation Solution
A signal processing circuit utilizing a CMOS switch with parallel MOSFETs of different channel types and a capacitor to switch the time constant of the filter circuit, allowing for noise removal without the need for a resistor element, thereby reducing circuit scale.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If the size of the resistor element is increased to achieve effective noise removal, then the noise removal capability is improved, but the circuit scale increases
Solution Approach 1:
The patent extracts the resistor element from the traditional RC filter circuit and replaces it with a CMOS switch. The switch's ON-resistance serves the function of the resistor, eliminating the need for a separate resistor component and reducing circuit scale while maintaining noise removal capability.
Solution Approach 2:
The patent changes the resistance parameter by utilizing the ON-resistance characteristic of the CMOS switch instead of a fixed resistor. By controlling the switch state (ON/OFF), the effective resistance changes dynamically, enabling time constant switching while using minimal circuit area.
2Object-affected harmful factors
If the time constant of the low-pass filter is increased to remove noise, then the noise removal is improved, but the settling time increases
Solution Approach 1:
The patent makes the time constant dynamic by using a CMOS switch that can change its ON-resistance value. The controller switches between different resistance states (first state with lower resistance, second state with higher resistance), allowing the time constant to be adjusted dynamically. This enables the system to achieve both fast settling (with smaller time constant) and effective noise removal (with larger time constant) at different stages.
Solution Approach 2:
The patent employs periodic switching of the CMOS switch between different states during the signal processing sequence. The switch transitions from a first state during sampling to a second state during noise removal, creating a time-varying filter characteristic that optimizes both speed and noise performance.
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 circuit effectively switches the time constant of the filter while minimizing circuit size, enabling efficient noise removal and reduced settling time.
Implementation Method 1
a CMOS switch including a first MOSFET and a second MOSFET having different channel types and connected in parallel... The controller switches a state of the CMOS switch between a first state in which the first MOSFET is in an ON state and a second state in which the first MOSFET is in an OFF state and the second MOSFET is in an ON state
Implementation Method 2
a capacitor electrically connected between an output of the CMOS switch and a ground potential
Data Source
AI summary
A signal processing circuit includes: a filter circuit that removes noise from a target signal; and a controller that controls the filter circuit. The filter circuit includes: a CMOS switch including a first MOSFET and a second MOSFET having different channel types and connected in parallel; and a capacitor electrically connected between an output of the CMOS switch and a ground potential. The controller switches a state of the CMOS switch between a first state in which the first MOSFET is in an ON state and a second state in which the first MOSFET is in an OFF state and the second MOSFET is in an ON state. An ON resistance value of the second MOSFET is higher than an ON resistance value of the first MOSFET.