Re: Why was the LM3900 and LM3909 discontinued ?

[Michael Black]

Anybody knows why National discontinued the LM3900 ? It seems
reasonably popular and, even today, many resellers carry the TI
version. Obsolete fab process ?

It served really no purpose.

I can remember when it came out, and it was born with a big datasheet
or application note that was loaded with things you could do with it.
But, most of it was novelty, "oh look, here's an LED flasher but you
can do all kinds of other things with it".

It got press early on, but it was rarely used in constructin articles
in the hobby magazines, unless someone used one of those novelty applications.
You had to add a whole IC just to flash an LED? The sorts of things where
it might be really useful, as a very low current LED indicator, you wouldn't
want to devote the space to.

I don't remember it as being particularly available, it must have been but
it never saw the saturation in places that sold to hobbyists that would
indicate it was a popular part.

I've never seen one in any piece of commercial equipment I've taken apart,
which does seem to be an indicator of how little use it saw in commercial
products.

It lasted for decades, but never really served much purpose.

ONe of the odd things is how long a lot of ICs have lasted. In the early
days there was so much turnover, as logic family A was replaced with logic
family B and so on, and as op-amps evolved until they got good. In
retrospect, it's a surprise that a lot of ICs did last so long, because
then the expecation seemed to be that something better would come along
soon to replace anything; after all that had already happened.

A lot of ICs have come and gone, often far more useful or interesting
than the 3909. I can't really fathom why the 3909 lasted so long.

Michael

 

[Michael Black]

Michael Black ([email protected]) writes:
Oops, ignore this, I read "3909" (the flasher) instead of "3900" (the
norton amplifier).

Michael

 

[mc]

It served really no purpose.

I can remember when it came out, and it was born with a big datasheet
or application note that was loaded with things you could do with it.
But, most of it was novelty, "oh look, here's an LED flasher but you
can do all kinds of other things with it". ....
A lot of ICs have come and gone, often far more useful or interesting
than the 3909. I can't really fathom why the 3909 lasted so long.

Whoa. LM3909 = low-voltage LED flasher. LM3900 = quad Norton amplifier.
Both are discontinued.

The LM3909 was useful -- it would flash a red LED from a 1.5-volt source, if
I recall correctly. At one point I reverse-engineered it and designed a
discrete-component substitute.

The LM3900 -- well, I couldn't see what it could do that an op-amp couldn't.

 

[Glenn Gundlach]

It served really no purpose.

I can remember when it came out, and it was born with a big datasheet
or application note that was loaded with things you could do with it.
But, most of it was novelty, "oh look, here's an LED flasher but you
can do all kinds of other things with it".

It got press early on, but it was rarely used in constructin articles
in the hobby magazines, unless someone used one of those novelty applications.
You had to add a whole IC just to flash an LED?  The sorts of things where
it might be really useful, as a very low current LED indicator, you wouldn't
want to devote the space to.

I don't remember it as being particularly available, it must have been but
it never saw the saturation in places that sold to hobbyists that would
indicate it was a popular part.

I've never seen one in any piece of commercial equipment I've taken apart,
which does seem to be an indicator of how little use it saw in commercial
products.

It lasted for decades, but never really served much purpose.

ONe of the odd things is how long a lot of ICs have lasted.  In the early
days there was so much turnover, as logic family A was replaced with logic
family B and so on, and as op-amps evolved until they got good.  In
retrospect, it's a surprise that a lot of ICs did last so long, because
then the expecation seemed to be that something better would come along
soon to replace anything; after all that had already happened.

A lot of ICs have come and gone, often far more useful or interesting
than the 3909.  I can't really fathom why the 3909 lasted so long.

  Michael

Useless tidbit. Phase Linear used the LM3900 in the model 1000
autocorrelator in the notch filters. It was an interesting alternative
to the Burwen noise reducing box. IIRC Burwen had a sliding corner
lowpass while Phase used 3 broad notch filters / gated by program
material in the respective band. The Phase Linear worked better after
removing the RC4136 (?) opamp and replacing it with a TL075.

GG

 

[RST Engineering \(jw\)]

I disagree. Its gain-bandwidth product is 3 MHz., triple the gbw of the
venerable LM324, which is why I designed it into (and still use it) in the
RST-523 Aircraft Navigation Receiver, still in production.

Jim

 

[xmeshman]

3900 discontinued ?

I recently ordered newly manufactured LM3900's.

After a close to 15 years of absence in electronic engineering
I skimmed the market for products to eventually start again.

My field was to a great part power supplies, and I've seen not much
real development, merely phasing in of circuits to single chips

I mainly applied the 3900 as a voltage regulator, 0.24 volt in volt out
at 12 volts / 120 amperes per IC, essentially ripple free with a 1 uf capacitor
at the output at full load. That due to it's high gain-bandwidth product.
They were often paralleled up to what I know, 600 amperes output by five
units without any externally applied current sharing, and frequently
used to start cars without any car/start battery mounted.

Not one single error or breakdown on any of several thousand delivered
power supply units.

O.K. LM359 is an alternative now, but it's more expensive per op amp
and only two per package, and with for my application not needed bandwidth.

So I today, see no application replacement available from the OP amp stock
of "regular" non Norton IC's

I can only look at some of the comments of the LM3900 with a broad smile.
and cite......
"Wovon man nicht sprechen kann, darüber muß man schweigen." inEng
"What we cannot speak of we must pass over in silence"