For me, this IC is an essential classic. It behaves almost exactly like a regular op-amp, you can have lots of fun experimenting with it. The two clamping diodes on the output protect the output transistors against glitches caused by complex load (speaker sets). The Boucherot's cell on the output is typical for power amps.
Generally speaking, this IC is slow, which means both higher THD and no problems with oscillations. The bad news: it's got audible noise on the output.
Aside of the original TDA2030, there's the TDA2030A, supposedly featuring higher power rating and lower distortion.
This IC only seems to be commonly available in some parts of the world. In others it's not. Reportedly, it can be replaced with an LM1875 by National Semiconductor. This chip has much lower noise, somewhat higher power rating (remember you won't be able to utilize that in the original circuit unless you're able to raise the rail voltage), lower distortion and is faster (which may potentially mean trouble in case of real poor PCB design). It doesn't need external clamping diodes, as these are already present on the chip. Actually, with its parameters, it's more likely a replacement for the TDA2040.
This note has been kindly contributed by someone called Noel, from Perth, Australia.