THE LM383 STORY (discontinued part)

This is the story of how National reverse engineered SGS's (ST Micro Electronics) TDA2002 chip audio amplifier.

It gives details about the design and challenges the designers faced.

The design of the LM383 forced SGS to come up with the TDA2003.

http://www.idea2ic.com/LM383/

I'm having troubles believing National Semiconductor copied SGS. NS had 100's of patents back then; the late 1970's NS had leading edge audio power amplifier IC's, the LM379S I worked with.

I'm inclined to think the same way as prairiedog. NatSemi is/was my favourite analog IC manufacturer. It's sad to see them go the way of former industry giants like RCA, probably due to commercial pressures. Everyone finds inspiration in someone else's work at times, but actual reverse engineering for something like an audio amplifier?

Apparently, this page is/was maintained by the designer himself, so this is his story. I can see that an audio amplifier could get copied since car-audio must have been good business way back then.

Most, if not all companies carry out competitive engineering analysis. An euphemism for reverse-engineering a competitor's capabilities.

Of course, if something truly innovative is found during that analysis, most likely it will be patented.

Therefore engineers in the company doing the reverse engineering must decide whether:
1- copy it outright, risking litigation and penalties later.
2- put their brains to work and obtain the same feature via a new approach, which circumvents the patent. Sometimes the differences in approach are razor thin.
3- license the technology.

Just like the other posters, I believe that National at the time was an analog IC powerhouse, which had enough expertise and capabilities to follow the second option. I cannot believe they would copy a design outright.

From what I read is that they did not copy it outright but from examining the operation and voltages on the pins figured out the internal workings of the TDA2002. They have not opened it up as far as I can find. So it is not an exact copy but rather a cloned functional copy into a T0-220 package.

"Back in the day" there were multiple analog-deep semi
houses. You could find the "generic" op amps in the same
root number, different prefix, from National, Fairchild,
Motorola, others. Near enough copies that they could be
interchanged the same as 74xx logic.

Of course the differentiated parts sold for more although
to a narrower base that had to be cultivated.

I'd bet that present day Class D audio parts kicked this
poor old fellow to the curb.

I have National Semiconductor databooks and Audio Handbooks back to 1973.
Reviewing them, they discuss the IC's in 1975 leading up to LM377, LM378, LM379 with schematics and explanations of overcoming the lateral-PNP problem.

The limit in 1976 was power dissipation in the power DIP package, so the LM383 is nothing more than a jump to TO-220 5-pin package. Same internals as its predecessors.
Interesting story about the TDA2002, but SGS-Thomson only had the TO-220 5 pin package. National already had the IC technology years beforehand.

Present-day Class-D parts generate much EMI and have higher distortion at low levels, but much greater efficiency and power output.

Class-D avoids the use of heatsinks in many instances.

That, plus the fact that nowadays all the cool gadgets are becoming "portable" (read: battery-powered), spelled doom for the class-AB audio amps.

Even if the device is AC-line powered, the higher efficiency afforded by class-D has allowed much more powerful devices.
For instance, in the 1970s an entry level PA system would be 100 to 200 watts per channel, nowadays for a similar price you can get easily 1000 or more watts per channel.