Programmable Amplifier Filter With Current Buffer for LNA Linearity
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Solution Overview
Problem
Low noise amplifiers (LNAs) face issues with linearity degradation due to large voltage swings across switches in differential mode and slow settling components from biased capacitors, which degrades performance and requires complex bootstrapping and large switch sizes.
Innovation Solution
The proposed amplifier design incorporates a current buffer between the output node and the transistor, with a capacitor network that draws and returns capacitive current, eliminating voltage swings across switches and reducing the need for bootstrapping, thus improving linearity and reducing switch size and power consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If switches are used in the I2V architecture for bandwidth programmability, then bandwidth control is achieved, but large voltage swings across switches degrade linearity
Solution Approach 1:
A current buffer is introduced as an intermediary component between the switch and the I2V architecture. The current buffer converts the voltage swing at its input to a current signal, preventing large voltage swings from appearing across the switch. This mediator allows the switch to control bandwidth while maintaining linearity by isolating the switch from the voltage swing effects.
2Stability of the object's composition
If unused capacitors are biased through large resistors for stability, then capacitor biasing is achieved, but slow settling components are introduced
Solution Approach 1:
The biasing mechanism is replaced by connecting the unused capacitor directly to a fixed bias voltage source instead of using a large resistor. This substitution eliminates the RC time constant associated with resistor-based biasing, thereby removing the slow settling component while maintaining stable capacitor biasing through the direct voltage connection.
3Strength
If large switch sizes are used to handle voltage swings, then voltage swing capacity is increased, but device complexity and power consumption increase
Solution Approach 1:
The current buffer acts as a mediator that transforms the voltage swing handling requirement. Instead of requiring the switch to directly handle large voltage swings, the current buffer absorbs the voltage swing at its input and presents a stabilized current output, allowing the use of smaller, less complex switches while maintaining the ability to handle the required signal dynamics.
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.