Multi-Path Broadband Amplifier With Parallel LNA Bandwidth Extension
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Solution Overview
Problem
Conventional amplifiers, such as dual-path and single-path DC coupled amplifiers, fail to achieve high frequency band edges comparable to narrowband amplifiers like low noise amplifiers (LNAs) and are hindered by the need for extensive support circuits, which slow down their performance.
Innovation Solution
A multi-path broadband amplifier design that combines a DC coupled amplifier with multiple low noise amplifiers (LNAs) in series and parallel, extending the bandwidth by incorporating AC coupling capacitors and high frequency pick-off nodes to create a summing node for combined signal output, thereby achieving a broader bandwidth.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If conventional single path DC coupled amplifiers are used, then the amplifier structure is simple, but the bandwidth is limited and performance is slowed down by extensive support circuits
Solution Approach 1:
The amplifier is divided into multiple parallel paths: a DC coupled amplifier path for low frequency signals and AC coupled LNA paths for high frequency signals. Each path is optimized independently, allowing the DC coupled path to be simple while the AC coupled paths provide high-speed performance without slowing down the overall system.
2Speed
If conventional dual path amplifiers are used, then the frequency response is split into two bands, but the high frequency band edge does not reach LNA performance levels
Solution Approach 1:
AC coupling capacitors serve as intermediaries that selectively connect the LNA paths for high frequency signals while blocking DC and low frequency signals. This allows the LNA paths to operate independently at high frequencies without being constrained by the DC coupled amplifier's bandwidth limitations, achieving LNA-level performance at high frequency band edges.
3Reliability
If extensive support circuits are added to DC coupled amplifiers, then gain adjustment and thermal compensation are improved, but the amplifier speed is reduced
Solution Approach 1:
The amplifier segments functions by using the DC coupled path for functions requiring stability (gain adjustment, thermal compensation) and AC coupled LNA paths for functions requiring speed (high frequency amplification). This segmentation allows each path to be optimized for its specific function without compromise.
Solution Approach 2:
The invention extracts the high-speed amplification function into separate AC coupled LNA paths, removing the constraint of extensive support circuits from the high-frequency signal path. The support circuits remain in the DC coupled path where they do not affect high-frequency performance.
4Speed
If AC coupling capacitors and multiple LNA paths are added, then the bandwidth is extended to upper frequency bands, but the device complexity increases
Solution Approach 1:
The DC coupled amplifier serves multiple functions: it handles low frequency signals directly and provides a signal source for the AC coupled LNA paths. The AC coupling capacitors serve dual purposes: blocking DC signals and enabling high-frequency signal transmission to LNA paths. This multi-functionality reduces the need for separate dedicated components.
Data Source
AI summary
An amplifier device having an extended bandwidth includes a DC coupled amplifier and multiple low noise amplifiers connected in series with one another and connected in parallel with at least a portion of the DC coupled amplifier. The DC coupled amplifier has a broad bandwidth, and each of the low noise amplifiers has a narrow bandwidth and a center frequency higher than a high end frequency of the broad bandwidth of the DC coupled amplifier. The extended bandwidth of the amplifier device is a combination of the broad bandwidth and the first narrow bandwidth.