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- LM1875
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- Last added
- 2012-05-08
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National Semiconductor LM1875 20W Audio Power Amplifier Datasheet
The LM1875 is a monolithic power amplifier offering very low distortion and high‑quality performance for consumer audio applications. It delivers 20 W into a 4 Ω or 8 Ω load on +25 V supplies and can exceed 30 W with an 8 Ω load at +30 V. The device includes internal current limiting and thermal shutdown for overload protection.
Key features include up to 30 W output power, THD of 0.015 % at 1 kHz, a wide supply range of 16 V‑60 V, high current capability of 4 A, 90 dB gain, 70 kHz power bandwidth, and a TO‑220 plastic package. Application hints cover PCB layout, stability, distortion control, thermal management, and recommended heat‑sink specifications.
National Semiconductor LM1875 specifications
| Maximum Output Power | Up to 30 W |
|---|---|
| THD (1 kHz, 20 W) | 0.015 % |
| Supply Voltage Range | 16 V‑60 V |
| High Current Capability | 4 A |
| Open‑Loop Gain | 90 dB |
| Power Bandwidth | 70 kHz |
| Ripple Rejection | 94 dB |
| Package | TO‑220 (plastic) |
Source: National Semiconductor LM1875 20W Audio Power Amplifier Datasheet
All National Semiconductor LM1875 documents by type
Ratings, dimensions and ordering codes, for selection and design work.
Questions answered in these manuals
How does the LM1875 protect against overheating?
It shuts down when the die reaches 170 °C and restarts when the temperature falls to about 145 °C, with a secondary shutdown at 150 °C if the rise continues.
From: National Semiconductor LM1875 20W Audio Power Amplifier Datasheet
What heat‑sink thermal resistance is required for a 50 V supply and 8 Ω load?
The total junction‑to‑ambient thermal resistance must be less than 4.2 °C/W; with a lubricated mica interface this means the heat sink itself must be under about 0.6 °C/W.
From: National Semiconductor LM1875 20W Audio Power Amplifier Datasheet
What is the maximum supply voltage for the LM1875?
The absolute maximum supply voltage is 60 V.
What is the typical THD at 20 W output?
Typical THD is 0.015 % at 1 kHz when delivering 20 W.