What this amp is and where it fits
The STMicroelectronics TDA7850 is a Class AB quad-channel audio amplifier delivering 85W per channel into a 2 Ohm load. It runs directly off a standard 12V automotive electrical system — the 8V to 18V supply range means no extra regulator needed for car audio head units or external amp modules. The through-hole 25-Flexiwatt package with formed leads is serviceable with a soldering iron; no hot-air station required for a field swap. Built-in mute, standby, and short-circuit/thermal protection reduce external BOM count and protect the speaker load during fault conditions.
85W per channel at 2 Ohm — what that means for the install
The headline rating of 85W x 4 into 2 Ohm tells you this amp is designed for low-impedance automotive speakers or parallel-wired loads. At 4 Ohm (typical aftermarket coaxials) the output will be lower, but the 2 Ohm capability gives headroom for subwoofer or high-power midbass channels without clipping. The Class AB linear topology means clean audio but higher quiescent current than a Class D — budget for adequate heatsinking in a sealed enclosure.
Temperature range — under-hood or trunk, it survives
Rated for -55°C to 150°C junction temperature, this die can handle the thermal extremes of a car interior in summer, a trunk-mounted amp near the exhaust tunnel, or even under-hood locations in heavy-duty vehicles. The 150°C TJ max is the silicon limit, not the case temperature — the 25-Flexiwatt package needs a proper heatsink to keep the junction below that in continuous operation at 85W.