Programmable Amplifier Filter Using Current-Buffered Capacitor Switching
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Solution Overview
Problem
Low noise amplifiers (LNAs) face issues with linearity degradation due to voltage swings across switches in differential mode operations, leading to distorted signals and the need for bootstrapping, which increases complexity and power consumption.
Innovation Solution
The proposed amplifier design incorporates a current buffer between the output node and the transistor, with a capacitor network that draws a capacitive current, reducing voltage swings and eliminating the need for bootstrapping, thus improving linearity and reducing power consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a set of switches is used in the I2V architecture for bandwidth programmability, then bandwidth can be adjusted, but voltage swing across the switches degrades linearity of the LNA
Solution Approach 1:
A current buffer is introduced as an intermediary component between the LNA output node and the capacitor network. This current buffer converts the voltage swing at the output node into a current signal, preventing direct voltage swing across the switches and capacitors, thereby maintaining linearity while enabling bandwidth programmability through the capacitor network.
Solution Approach 2:
The patent replaces the conventional voltage-mode switching mechanism with a current-mode operation. Instead of switching capacitors directly at the output node (voltage mode), the invention uses a current buffer to drive the capacitor network in current mode, eliminating the voltage swing across switches and improving linearity.
2Reliability
If unused capacitors are biased through a large resistor to maintain voltage, then the capacitors remain functional, but slow settling components are introduced in the LNA
Solution Approach 1:
The current buffer acts as an intermediary that provides a low-impedance current source for biasing the capacitor network. This replaces the need for large biasing resistors, as the current buffer can quickly charge and discharge the capacitors without introducing slow settling components, while maintaining proper capacitor functionality.
Solution Approach 2:
The invention changes the biasing mechanism from high-resistance voltage biasing to low-impedance current biasing. By using a current buffer with low output impedance, the capacitors are quickly charged to their required voltages, significantly reducing the settling time compared to traditional resistor-based biasing.
3Manufacturing precision
If bootstrapping is implemented to maintain switch linearity, then linearity is improved, but device complexity and power consumption increase
Solution Approach 1:
The patent substitutes the complex bootstrapping mechanism with a simpler current buffer approach. Instead of using additional active circuits to dynamically adjust switch gate voltages (bootstrapping), the invention uses a current buffer to directly drive the capacitor network in current mode, eliminating voltage swing across switches and simplifying the overall circuit architecture.
4Manufacturing precision
If bootstrapping is implemented to maintain switch linearity, then linearity is improved, but power consumption increases
Solution Approach 1:
The current buffer-based current mode operation replaces the power-intensive bootstrapping circuitry. The current buffer efficiently drives the capacitor network without requiring the additional power that bootstrapping circuits consume, while maintaining switch linearity through current-mode operation that eliminates voltage swing across switches.
Data Source
AI summary
The disclosure provides an amplifier. The amplifier includes a first transistor that receives a first input and generates a first load current. A first output node is coupled to a power supply through a first load resistor. The first load resistor receives the first load current. A first capacitor network is coupled to the first output node and draws a first capacitive current from the first output node. A first current buffer is coupled between the first output node and the first transistor. A current through the first current buffer is a summation of the first load current and the first capacitive current.