H03F 3/181
Low-frequency amplifiers
Official title: Low-frequency amplifiers, e.g. audio preamplifiers
H03F3/181 (Low-frequency amplifiers) appears on 2,007 US grants and 2,104 published applications in this corpus.
Search patents in H03F- Granted patents
- 2,007
- Published applications
- 2,104
- Assignees
- 655
- Inventors
- 2,816
- Latest grant
- 6 Oct 2026
Filings by year
| Year | Granted patents | Published applications |
|---|---|---|
| 1976 | 8 | 0 |
| 1977 | 13 | 0 |
| 1978 | 5 | 0 |
| 1979 | 6 | 0 |
| 1980 | 9 | 0 |
| 1981 | 13 | 0 |
| 1982 | 6 | 0 |
| 1983 | 5 | 0 |
| 1984 | 9 | 0 |
| 1985 | 12 | 0 |
| 1986 | 7 | 0 |
| 1987 | 2 | 0 |
| 1988 | 4 | 0 |
| 1989 | 2 | 0 |
| 1990 | 4 | 0 |
| 1991 | 2 | 0 |
| 1992 | 4 | 0 |
| 1993 | 3 | 0 |
| 1994 | 2 | 0 |
| 1995 | 3 | 0 |
| 1996 | 9 | 0 |
| 1997 | 8 | 0 |
| 1998 | 9 | 0 |
| 1999 | 5 | 0 |
| 2000 | 11 | 0 |
| 2001 | 8 | 0 |
| 2002 | 7 | 9 |
| 2003 | 6 | 11 |
| 2004 | 8 | 17 |
| 2005 | 10 | 24 |
| 2006 | 23 | 23 |
| 2007 | 16 | 30 |
| 2008 | 22 | 43 |
| 2009 | 21 | 45 |
| 2010 | 32 | 35 |
| 2011 | 40 | 57 |
| 2012 | 50 | 62 |
| 2013 | 52 | 59 |
| 2014 | 54 | 77 |
| 2015 | 68 | 115 |
| 2016 | 126 | 124 |
| 2017 | 153 | 150 |
| 2018 | 151 | 135 |
| 2019 | 150 | 148 |
| 2020 | 175 | 186 |
| 2021 | 131 | 119 |
| 2022 | 140 | 147 |
| 2023 | 129 | 149 |
| 2024 | 95 | 135 |
| 2025 | 101 | 106 |
| 2026 | 78 | 98 |
By publication year. Applications have been published since 2001. 2026 runs to 8 Oct.
Subgroups
Granted patents
Recent patents
- Digital-to-analog converter, chip, and electronic device6 Oct 2026US 12,756,402 B2Sg Micro Corp
- Auto-recovery overcurrent protection for audio notification appliance circuit in fire protection system6 Oct 2026US 12,756,974 B2Tyco Fire & Security GmbH
- Method for adaptively adjusting start-up time of audio amplifier and associated system on chip29 Sep 2026US 12,750,016 B2Elite Semiconductor Microelectronics Technology Inc.
- Semiconductor device and electronic apparatus15 Sep 2026US 12,739,580 B2Seiko Epson Corporation
- Systems and methods for synchronizing and rendering audio signals via an auxiliary synchronization back channel8 Sep 2026US 12,732,752 B2Lenbrook Industries Limited
- Speaker System8 Oct 2026US 2026/0313277 A1
- Amplifier system with output stage24 Sep 2026US 2026/0291444 A1Harman International Industries, Incorporated
- Zero-common-mode modulation with digital feedback to damp common-mode resonance and suppress cross-over distortion24 Sep 2026US 2026/0291447 A1Monolithic Power Systems, Inc.
- Switching amplifiers27 Aug 2026US 2026/0254416 A1Cirrus Logic International Semiconductor Ltd.
- Switching amplifiers27 Aug 2026US 2026/0254417 A1Cirrus Logic International Semiconductor Ltd.
Most cited
By later US patents
- Bypassing amplification301US 8,063,698 B2Bose Corporation · 2011
- Acoustic signatures in a playback system187US 8,930,005 B2Sonos, Inc. · 2015
- Monolithic class D amplifier170US 5,973,368 A1999
- Load impedance detector for audio power amplifiers161US 4,549,147 AVictor Company of Japan, Ltd. · 1985
- RF amplifier architecture and related techniques141US 8,824,978 B2Eta Devices, Inc. · 2014