Cascode Low-Noise Amplifier Feedback for Lower Noise Figure
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Solution Overview
Problem
Common-gate Low Noise Amplifiers (LNAs) exhibit higher noise levels compared to common-source architectures, necessitating improvements in noise performance due to additional components required for impedance and noise matching, which increase area and noise.
Innovation Solution
The implementation of a cascode-connected amplifier with a tuning circuit for phase-shifting the output and a feedback circuit that enhances gain by providing a phase-shifted feedback signal to the amplifier, coupled with an impedance matching circuit to improve noise performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If common-source architecture is used for LNA, then noise performance is improved, but additional components for impedance and noise matching increase area and complexity
Solution Approach 1:
The patent implements a feedback circuit that feeds a portion of the output signal back to the input, creating positive feedback to enhance gain and improve noise performance. The feedback network includes capacitors and resistors configured to provide the necessary phase and amplitude conditions for constructive feedback, reducing the need for additional impedance matching components
Solution Approach 2:
The patent modifies the circuit parameters by using specific capacitor values (C1, C2, C3) and resistor values (R1, R2, R3) to optimize the feedback network's transfer function. By adjusting these parameters, the circuit achieves improved noise performance and gain enhancement without requiring additional complex impedance matching components
2Area of stationary object
If common-gate architecture is used for LNA, then area is reduced, but noise level increases
Solution Approach 1:
The feedback circuit in the patent provides positive feedback to the common-gate amplifier, enhancing its gain and improving noise performance. The feedback network is designed to compensate for the inherent noise disadvantages of common-gate architecture while maintaining the area efficiency of this configuration
Solution Approach 2:
The patent introduces dynamic elements (capacitors and resistors in feedback configuration) that allow the circuit to adapt its noise and gain characteristics. The feedback network dynamically adjusts the effective input impedance and noise figure based on operating conditions, enabling the common-gate architecture to achieve noise performance comparable to or better than traditional designs
Data Source
AI summary
Low noise amplifier circuit. The low noise amplifier circuit includes an amplifier that amplifies an input to provide an output. The amplifier is coupled to an input terminal. The circuit also includes a device in a cascode connection with the amplifier. The circuit further includes a tuning circuit coupled to the device to phase shift the output. Further, the circuit includes a feedback circuit that is responsive to a phase-shifted output to enhance gain of the amplifier. The feedback circuit is coupled to the tuning circuit and the amplifier.