Product Overview
56W class-AB monolithic power amp IC for Gainclone and hi-fi builds
Condition
Unused, NOS – New Old Stock. Excellent condition with nothing out of the ordinary noted. Visual inspection OK. Part of our ongoing recovery from legacy electronics supply chains.
Ships same business day. Reliable parts since 1999. Honest pricing, no nonsense.
Product Overview
National Semiconductor LM3875T is a high-performance monolithic audio power amplifier from the Overture series. Supplied in the TO-220-11 straight-lead package, it is designed for through-hole mounting and external heatsinking. This IC is widely used in "Gainclone" amplifier builds for its ability to deliver strong output power with a minimal external parts count. With integrated SPiKe protection and class-AB architecture, it combines output capability and built-in fault management in a single device.
Key Features
- Brand: National Semiconductor
- Model: LM3875T
- Package: TO-220-11 (non-isolated tab, straight leads)
- Continuous output power: 56W into 8Ω at ±35V
- Continuous output power: 40W into 4Ω at ±28V
- THD+N: 0.06% typical (20Hz–20kHz)
- Slew rate: 11 V/µs
- Signal-to-noise ratio: >95dB typical
- Quiescent current: 30mA typical
- Integrated SPiKe protection (overvoltage, overload, thermal)
Applications
- DIY Gainclone stereo amplifiers
- High-fidelity home audio power stages
- Active speakers and studio monitor builds
- Compact integrated amplifiers
- Audio lab test amplifiers and bench setups
- Restoration of legacy Overture-based amplifier designs
Frequently Asked Questions
What package is the LM3875T?
The "T" version is supplied in a TO-220-11 package with straight leads for vertical PCB mounting. The metal tab is not isolated.
Is the tab electrically isolated?
No. The tab is internally connected to the negative supply (V-). An insulating pad and shoulder washer are required if mounting to a grounded heatsink.
How much power can it deliver?
It can deliver up to 56W into 8 ohms with ±35V supplies and 40W into 4 ohms with ±28V supplies, within specified operating conditions.
Does it include protection circuitry?
Yes. It features National Semiconductor's SPiKe protection system, which monitors safe operating area and protects against overload, short circuit, and thermal events.
Are there design constraints?
The device is internally compensated for a closed-loop gain of 10 or higher. Proper supply bypassing and PCB layout are critical to prevent oscillation.
A single-chip amplifier that helped define a generation of DIY hi-fi. Give it a solid power supply and clean layout, and it will do the rest.
