Class-D Audio Amplifiers Patents: Leader, Long Tail & Trends 2026
- 45 of 108 records sit with the top five assignees — 41.7% of all filings in scope, with a single leader at 12 records.
- Filings peaked in 2018 at 15 and have not returned to that level since; the 2022 midpoint sits at just 2.
- 94.4% of records carry an H03F amplifier classification, but only 8.3% touch H03K pulse-technique claims — a narrow band around the switching stage itself.
What this landscape covers
This review covers 108 published records filed between 2015 and mid-2026 that combine class-D amplifier or digital audio amplifier language with technical claim details such as THD+N, idle power, EMI from switching, speaker protection or modulation scheme, restricted to H03F, H03F1/H03F3 and H04R3 classifications. That combination narrows the set to amplifier architecture and modulation-control claims rather than general audio circuitry.
Publication lags filing by roughly 18 months, so the most recent year in the trend is understated by construction — the 2026 figure is a partial year, not a genuine trough.
Filing trend and technology composition
Two views of the same 108 records: how filing volume has moved year over year, and which IPC subclasses the claims actually sit in.
A 2018 peak that has not repeated
Filings ran to 15 in 2018, the high point of the window, then fell back; the 2022 midpoint of 2 records shows the decline is not a short dip. With growth flat-to-declining and 2026 still an open year, this reads as a maturing filing cycle rather than an emerging one.
Concentrated in the amplifier stage, not the loudspeaker or digital-processing layers
H03F amplifier claims cover 94.4% of the 108 records, confirming the search scope. Loudspeaker/transducer integration (H04R, 10.2%) and pulse-technique circuits (H03K, 8.3%) are present but far thinner, and digital-processing crossover (G06F, 2.8%) and memory-adjacent claims (G11C, 1.9%) are minor threads rather than established sub-fields.
Shares are the percentage of the 108 records in scope. A patent can carry several IPC classes, so the shares add up to more than 100%.
Go deeper on Class-D Audio Amplifiers with Eureka
This page is one run against one query. Ask Eureka your own question about class-d audio amplifiers and every answer comes back with the patent numbers behind it.
Try EurekaThe most-cited records in this set
Method and Apparatus for Efficient and Distortion Compensated Digital Class-D Amplifier Ternary Modulation Scheme
Filed by Telefonaktiebolaget L M Ericsson, this 2013 filing (US20130222063A1) addresses distortion in a ternary-modulation class-D amplifier by symmetrically enlarging output pulses around their centre position and generating compensating pulses to correct the resulting waveform error.Abstract condensed from the original filing.
| # | Publication no. | Patent title | Citations |
|---|---|---|---|
| 1 | US20060012428A1 | Class-D amplifier | 24 |
| 2 | US20190149107A1 | Low power dissipation high performance class-d amplifier | 19 |
| 3 | US20170077882A1 | Class-d amplifier with pulse-width modulation common-mode control and associated method for performing class-… | 18 |
| 4 | US7265617B2 | Class-D amplifier | 16 |
| 5 | US20120223772A1 | Multilevel class-d amplifier | 13 |
| 6 | US20120025910A1 | Switching amplifier with enhanced supply rejection and related method | 13 |
| 7 | US20120013402A1 | Closed-loop class-d amplifier with modulated reference signal and related method | 13 |
| 8 | US8212612B2 | Closed-loop class-D amplifier with modulated reference signal and related method | 13 |
| 9 | US10778160B2 | Class-D dynamic closed loop feedback amplifier | 12 |
| 10 | US20090160553A1 | Distortion suppression circuit for digital class-d audio amplifier | 11 |
Citation counts favour older records that have had more time to accumulate cites within this corpus — read them as markers of influence on later filings, not as a signal that a claim is still commercially central.
Each row carries its publication number; clicking a row searches Eureka by that number.
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Three read-throughs from the concentration, geography and citation figures above.
The leader board is short, and the gap below it is real
45 of 108 records belong to the top five assignees, with the single leader holding 12. The top ten together hold 65.7% of records, meaning roughly a third of the field is split across 25 more names each with a handful of filings — a long tail rather than a crowded middle.
Activity has cooled since its peak
The filing curve rose to 15 records in 2018 and has not returned there; by 2022 annual filings were down to 2. That pattern points to a technology where the core architecture claims were staked out mid-decade, with newer work narrower in scope.
US-centric filing with a secondary European cluster
United States receiving-office filings outnumber the next largest office, EPO, by more than three to one. China's 6 filings are modest against that backdrop, suggesting this remains a US- and Europe-anchored filing strategy rather than a China-first one within this dataset.
Eureka can read the same corpus for gaps instead of for coverage: under-claimed branches adjacent to class-d audio amplifiers, with the prior art for and against each one.
Who is active, and where the claim space is thin
The ranked leaders hold most of the volume, but recent-year filing has gone quiet even among them — a sign the next wave of activity may come from outside the current leader board.
A single leader, no close second
The top assignee holds 12 records against 7 at fifth place and 4 at tenth — a steep drop-off rather than a plateau, which usually means the leader staked foundational claims early and later entrants filed narrower improvements around them.
Recent-year activity has nearly stopped among leaders
Of the assignees tracked for recent-year momentum, only one shows a filing in the latest year; the rest show none. That is consistent with the broader flat-to-declining trend rather than a leader-specific pause.
Co-filing is rare in this set
Only two co-assignee pairings appear across the 108 records, both linked to the same corporate filer and named inventors. Most activity here is filed solo rather than through joint ventures or cross-licensed development.
| Assignee | Recent year | YoY |
|---|---|---|
| QSC LLC | 1 | — |
| Cirrus Logic International Semiconductor Ltd | 0 | — |
| Richtek Technology Corporation | 0 | — |
| MediaTek Inc. | 0 | — |
| ST-Ericsson SA | 0 | — |
| Eutech Microelectronics | 0 | — |
| Harman International Industries, Inc. | 0 | — |
| Axign BV | 0 | — |
Where to take this analysis
The figures above describe where filing has been. Two follow-on questions decide what to do with that.
Check freedom-to-operate against the leader's claim set
With one assignee holding 12 of 108 records and a steep drop to the rest of the field, a new filing near the amplifier core should be checked against that leader's claims before drafting.
Explore assignee claims in EurekaWatch the under-claimed branches for entry points
Thin IPC coverage in areas like idle-power circuits or speaker-protection feedback suggests room to file without crowding an incumbent's exact claim language.
Map white space in EurekaCommon questions on class-D amplifier patents
Within the 108 records in this dataset, one assignee leads with 12 records, well ahead of the fifth-ranked assignee at 7 and the tenth-ranked at 4. The top five assignees together hold 45 records, or 41.7% of all records in scope, and the top ten hold 65.7%. Beyond that, coverage spreads thinly across 25 further assignees, each with only a small number of filings, so the field has a clear leader but a genuine long tail rather than a tight cluster of equally sized competitors.
No, the trend in this dataset is flat to declining. Annual filings peaked at 15 in 2018 and had fallen to 2 by the 2022 midpoint, with no clear recovery visible since. Note that the most recent year is a partial figure because publication typically lags filing by around 18 months, so the true 2026 count will revise upward, but the multi-year direction through the peak is not in question.
The overwhelming majority, 94.4% of the 108 records, carry an H03F amplifier classification, confirming that most claims address the amplifier stage itself rather than adjacent systems. Loudspeaker and transducer integration under H04R appears in 10.2% of records, and pulse-technique circuitry relevant to switching under H03K appears in 8.3%. Crossover into digital data processing (G06F) or gain control (H03G) is present but minor, each near 2.8%, indicating those are secondary threads rather than established sub-fields within this scope.
The IPC composition points to thinner coverage outside the core H03F amplifier claims — areas like idle-power reduction, speaker-protection feedback, and EMI suppression at the switching frequency show up as secondary classifications rather than dense clusters. Given that co-assignee collaboration is rare in this dataset, with only two identified pairs, most of this space has been filed solo, which may leave room for partnership-based filings that existing solo filers have not pursued. Any specific entry point should still be checked against the leading assignee's claims given how concentrated the top of the field is.
This Telefonaktiebolaget L M Ericsson filing from 2013 addresses distortion in ternary-modulation class-D amplifiers through a specific pulse-enlarging and compensation technique, and it is used here as the representative record for the modulation-scheme branch of this landscape. It is not the most-cited record in the set — that distinction belongs to older filings with more time to accumulate citations — but its claim structure is a clear, well-documented example of the ternary-modulation approach that later filers have had to design around or improve upon.
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Disclaimer. This page is generated from Patsnap Eureka data drawn from a limited snapshot of global patent and scientific-literature records, and is provided for general information and reference only.
Patent data carries inherent limitations: recent filings (typically the most recent 18–24 months) are under-counted due to standard publication lag; counts may be reported at either a patent-family or a patent-record basis and are not always directly comparable; classification, applicant-name, and citation data may contain errors, duplicates, or omissions; and the underlying search query defines and constrains the scope shown. As a result, the analysis may be incomplete or inaccurate and may not reflect the full technology landscape.
Nothing on this page constitutes an exhaustive prior-art, novelty, freedom-to-operate, or validity search, nor does it constitute legal, financial, investment, or professional advice, and it should not be relied upon as such. Any patent, commercial, or strategic decision should be verified independently and reviewed with qualified patent, legal, and domain professionals. Patsnap makes no warranties, express or implied, as to the accuracy, completeness, or fitness for any particular purpose of the information presented.
Machine translation. Assignee and organisation names originally recorded in Chinese, Japanese or Korean have been rendered into English by an AI translation step so that the tables stay readable. These renderings are best-effort and may not match a company’s registered English name; the original name is what the underlying patent record carries, and it is what any Eureka query launched from this page uses.