Push-Pull Differential LNA With Buffered 50 Ω Impedance Matching
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Solution Overview
Problem
Current low noise amplifiers (LNAs) for wireless devices face challenges in reducing noise figure, design area, and power consumption, particularly due to high input and output impedances, which complicate impedance matching and limit operational bandwidth.
Innovation Solution
A full-differential LNA with a push-pull structure and reduced impedance matching devices, including capacitors and inductors, is designed to control DC components and match impedances, employing a buffer to manage direct current and using a differential inductor patterned in a symmetrical strip line structure for efficient impedance matching.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a cascode amplifier structure is used, then current reuse and stability are achieved, but input and output impedances become high making impedance matching difficult and limiting operational bandwidth
Solution Approach 1:
The amplifier is divided into separate push-pull stages with distinct input and output impedance matching networks. The input stage uses a differential pair with inductive degeneration for low input impedance, while the output stage uses a complementary push-pull configuration with separate impedance matching, allowing each segment to be optimized independently for its specific function.
2Use of energy by moving object
If a push-pull amplifier structure is used, then power efficiency and low input impedance are achieved, but output impedance becomes high making impedance matching difficult
Solution Approach 1:
An output buffer stage is introduced as an intermediary between the push-pull amplification stage and the output load. This buffer has low output impedance and provides current buffering, effectively decoupling the high efficiency push-pull stage from the impedance matching requirement, allowing the push-pull stage to operate at maximum efficiency while the buffer handles the impedance transformation.
3Ease of operation
If multiple impedance matching devices are used, then impedance matching is achieved, but design area increases
Solution Approach 1:
The input and output impedance matching networks are merged into the amplifier stages themselves rather than being separate components. Inductive degeneration resistors serve dual purposes of setting bias current and providing input impedance matching, while the load inductors provide both gain and output impedance matching, reducing the total component count and design area.
Data Source
AI summary
Provided is an amplifier including: an amplifier circuit receiving differential signals to generate amplified differential signals; a buffer generating buffered signals by buffering each signal generated by controlling a direct current (DC) component of the differential signals; and an impedance matching device coupled between two terminals wherein each of the buffered signals is added with each of the amplified differential signal.