LM324 - Again but in more detail

The quad is nearly twice as fast as the dual which I wouldn't have supposed.

It's still a great chip for very cost-constrained applications, this little "toy" analog synthesizer aside from the battery boost IC, uP, and digital delay IC the analog audio path is all '324s and discrete transistors.

That really is a remarkable app note.

John

The really great (would that all be as well written!) app note points out that only on the quad die does the chip get close to the capacitance specs...

John :-#)#

Yikes. The 324 shows visible crossover distortion at 60 Hz!

But then, some people like distortion.

Full schematic of the original toy, this one didn't even have a uP. Audio output is a "TPA611A2DR."

The outputs of the two sections that carry actual audio signal rather than acting as control voltage processors/buffers look to be thoughtfully terminated to ground rather than the mid-point so those sections are always sourcing current and there isn't a cross-over problem.

'visible' isn't a measure of distortion.

-3 points, units.

Seriously, you DO know that class B is better for battery power, but class AB or A for distortion? Add that to the fact that class B has lower component precision requirements, and we have a niche winner!

If I can see it on an oscilloscope, it's a lot of distortion.

I know that there are modern RRIO opamps that are faster, use less power, and have no crossover distortion.

The LM324 is 45 years old. Did Widlar design the 324?

We met Widlar's girlfriend at the bar at the Washington Square Bar and Grille, while he was living in Mexico. She was amazed that anyone had heard of him. She didn't know what he did, but had interesting stories.

seems unlikely, the LM324 was released in 1972, Widlar wasn't working for National at the time (unless it was a off-the-record contractor kind of deal)

not exactly a lot of "genius" to the LM324 circuit, it's the kind of design that makes you wonder why it took until even '72 for anyone to make that in a quad.

Not exactly off the record.

The GF said that they had a kitchen table with a heavy oilcloth tablecloth. There were drawings of chips under it, and she was never allowed to see them. He was paranoid about that. A couple of times a year, he'd roll them up, fly up to National, and revolutionize linear IC design again.

She was worried about his drinking.

What year was this?

Regis McKenna apparently said Widlar and Talbert were responsible for everything National did in the 70s but he left National in '69 according to my history books so how the f*ck would he know.

my guess is by the mid-late 70s Widlar's best work was behind him he was too into the booze to be "revolutionizing" anything. if it was all off-the-record stuff though then who knows. can anyone confirm anything Widlar did for them for sure from 74-81 other than the LM10?

Well if he did the LM324 I can see why he wouldn't want his name attached to it. It's definitely meatloaf, not filet mignon.

Meatloaf is okay sometimes.

Wasn't he the one who died in his Porche? Compare that to Bob Pease dying in his Beetle. I believe Bob actually died of an aneurysm which made him crash.

The references on wikipedia said Widlar died of a heart attack in Mexico while jogging or something. possibly related to his (former?) alcoholism.

Never heard anything about extenuating circumstances in Pease's death the ME would be able to determine that I would imagine though? idk if those records are available to the public at this point. area it happened was a treacherous piece of road, swing-axle rear ends were easy to lose control of, he was distraught and not focusing on his driving in a difficult car even in the best of times. and it understeered right out from under him. Overconfidence caught up would be my guess with no further info.

The Volt has a tendency to understeer also and I've nearly lost it a couple times on sharp curves when I wasn't paying full attention but with the computer's help the car was able to correct. 45 mph head first into the woods is a very bad day but probably survivable in a modern car with 12 airbags and a seatbelt but in a Bug without wearing a belt, nah.

I drove a late 70s Superbeetle one time even that thing was nuts, like putting around in a clown car from the circus. you could never pay me enough to take that jalopy out on the open road regularly. But I'm not "of the era"

A "type" of engineer. Building the future on the job, but then on their free time wanna drive 50 year old jalopys and use flip-phones from 20 years ago. ????????

Widlar wrote at length about his designs, and they were all about clever circuit and fab tricks, which added plenty of complexity, to get special performance. There's no sign of any of that in the LM324. It doesn't have the Widlar look.

That was James Dean?

Gerhard

LM324 was revolutionary in its time. As was the bandgap voltage reference. Ditto the Widlar current mirror.

I agree it lacks Widlar's flair, somehow I always thought of Dobkin but I could be mistaken. I thought the LM324 and it's derivative LM339 were progressions from the 1971 LM311 which may have been the first to use PNP input stage once they managed to fab half decent monolithic PNP ?

piglet