Push-Pull Amplifier Layout for Wideband Harmonic Rejection
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Solution Overview
Problem
Wideband power amplifiers face challenges with harmonic frequencies and intermodulation products falling within the carrier frequency band, leading to performance degradation and inefficient designs due to the need for band-specific filters, which complicates deployment and reduces efficiency.
Innovation Solution
A push-pull amplifier arrangement with separated ground planes and DC-blocking components, allowing the amplifier devices to operate in both differential and common modes with low impedance at common mode over a large bandwidth, enabling efficient operation and reduced distortion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If wideband power amplifiers are used to cover multiple frequency bands, then the bandwidth capability is improved, but harmonic frequencies and intermodulation products fall within the carrier frequency band causing performance degradation
Solution Approach 1:
The patent segments the amplifier operation into differential mode and common mode. The push-pull configuration with separated ground planes allows the amplifier to process fundamental frequencies in differential mode while even-order harmonics and intermodulation products appear in common mode, enabling selective rejection of unwanted signals.
Solution Approach 2:
The patent converts the harmful effect of harmonics and intermodulation products falling within the carrier band into a beneficial separation mechanism. By utilizing the inherent mode differentiation in push-pull operation, unwanted signals are automatically routed to common mode where they can be rejected, turning a performance-degrading issue into a filtering mechanism.
2Object-affected harmful factors
If class-A mode operation is used to reduce intermodulation products and harmonic content, then distortion is reduced, but energy efficiency deteriorates
Solution Approach 1:
The patent employs dynamic operation by utilizing class-B or class-AB push-pull amplifier operation instead of static class-A operation. The push-pull configuration dynamically switches between active devices based on the signal phase, maintaining low distortion through mode differentiation while significantly improving energy efficiency by allowing devices to remain off during portions of the cycle.
Solution Approach 2:
The patent changes the operational parameters by introducing separated ground planes and specific impedance configurations that enable mode differentiation. This parameter change allows the amplifier to achieve low distortion performance similar to class-A but with the energy efficiency of class-B or class-AB operation.
3Use of energy by moving object
If push-pull class-B amplifier configuration is used to improve energy efficiency, then energy efficiency is improved, but achieving ideal load terminations for both fundamental frequency and even order tones becomes challenging
Solution Approach 1:
The patent segments the load termination requirements by creating separate ground planes for differential and common mode operations. This segmentation allows independent optimization of impedance conditions for fundamental frequencies (differential mode) and even-order harmonics (common mode), simplifying the overall termination configuration.
Solution Approach 2:
The patent introduces separated ground planes as an intermediary structure that mediates between the amplifier devices and the load. These ground planes provide the necessary impedance transformations and mode separation, enabling ideal load terminations for both differential and common mode signals without requiring complex external networks.
4Ease of manufacture
If only n-type devices are used in push-pull configuration, then device availability is improved, but the fundamental frequency is excited in differential mode and even order tones in common mode requiring Z11 = Z22 = -Z12 which is very challenging over large bandwidth
Solution Approach 1:
The patent creates equipotential ground planes for differential and common mode operations. By providing separate ground references, the circuit achieves equipotential conditions that simplify impedance matching requirements, allowing Z11 = Z22 without the restrictive Z11 = -Z12 condition, thereby enabling wideband operation with n-type devices only.
Data Source
Figure 1~2A
Figure 2B~3A
Figure 3B~4A
AI summary
The present disclosure relates to an amplifier arrangement (1, 100, 200) comprising a first amplifier device (2, 102, 202) and a second amplifier device (3, 103, 203) where each amplifier device (2, 3; 102, 103; 202, 203) is connected to an input circuit (8, 108) and has a first type output terminal (4, 6; D) and a second type output terminal (5, 7; S), where the output terminals (4, 6, D; 5, 7, S) are connected to an output circuit (9, 109, 109'). The first type output terminal (4, D) of the first amplifier device (2, 102, 202) is connected to the second type output terminal (7, S) of the second amplifier device (3, 103, 203) by means of a first connection (10, 110), and the first type output terminal (6, D) of the second amplifier device (3, 103, 203) is connected to the second type output terminal (5, S) of the first amplifier device (2, 102, 202) by means of a second connection (11, 111). The first type output terminal (4, D) of the first amplifier device (2, 102, 202) and the first type output terminal (6, D) of the second amplifier device (3, 103, 203) are electrically separated in the output circuit (9, 109, 109'), and the second type output terminal (5, S) of the first amplifier device (2, 102, 202) second type output terminal (7, S) of the second amplifier device (3, 103, 203) are electrically separated in the output circuit (9, 109, 109').