Favorite Cheap and Useful Part? Lemme know.

[John Larkin]

Then it becomes the world's only open-emitter opamp!

Back in the Motorola days (I don't know if ON Semi has changed it),
their LM324 had the *worst* crossover distortion known to man. I
actually blacklisted Motorola as an LM324 vendor when I was with
GenRad.

Even with better vendors I always biased the output stages as class-A
when used in active filters.

...Jim Thompson

All 324's have very asymmetric output pullup/pulldown currents and
slow, asymmetric slew rates, too. Cheap and worth it.

John

 

[John Larkin]

The 324 has *no* crossover distortion when used as intended,
and works as good as any 1MHz GBW opamp. Read the schematics.
ICs are *not* black boxes.

How do you mean "as intended"? National's original datasheet (9 sheets
of it!) shows lots of examples where the output is DC unloaded, and
will have lots of crossover distortion.

With a large-signal frequency range of 5 KHz, it's nowhere near "as
good as any 1MHz GBW opamp".

John

 

[Winfield Hill]

Jim Thompson wrote...

Even with better vendors I always biased the output
stages as class-A when used in active filters.

Accckk, LM324 and active filters in the same sentence?!
Have you no shame?

Thanks,
- Win

whill_at_picovolt-dot-com

 

[John Woodgate]

I read in sci.electronics.design that Winfield Hill

Used as an ordinary opamp with split +/- supplies and loads to
ground, the LM324 has serious crossover distortion at moderate
frequencies, as John says. But used in a distinctly single-
supply fashion, e.g. with Vee at ground, AND with a resistive
load to ground, the LM324 will have no crossover distortion,
just as Russell asserted.

The output stage can be biased up to prevent crossover distortion with
split supplies as well as with single-ended supplies.

 

[John Popelish]

Jim Thompson wrote...

Accckk, LM324 and active filters in the same sentence?!
Have you no shame?

Why? At sub hertz frequencies they do very nicely.

 

[Jim Thompson]

Jim Thompson wrote...

Accckk, LM324 and active filters in the same sentence?!
Have you no shame?

Thanks,
- Win

whill_at_picovolt-dot-com

I'm dating myself (as if I haven't already)... remember 300- and
1200-baud modems ?

...Jim Thompson

 

[John Larkin]

Why? At sub hertz frequencies they do very nicely.

A 324 output looks like hell at 60 Hz. I tried using them in
electronic AC power meters and they weren't anywhere near up to the
task.

John

 

[Keith R. Williams]

I'm dating myself (as if I haven't already)... remember 300- and
1200-baud modems ?

Umm, do you mean 300 and 1200bps? Yes, I remember 110 and 134.5
too. It's not like Lincoln was in the Whitehouse then. ;-)

 

[John Woodgate]

I read in sci.electronics.design that John Larkin <jjlarkin@highlandSNIP
techTHISnologyPLEASE.com> wrote (in <i9n000h8iroodgpf5d40rpu3dr5dkg6n36@
4ax.com>) about 'Singing the praises of the LM324', on Sat, 10 Jan 2004:

A 324 output looks like hell at 60 Hz. I tried using them in
electronic AC power meters and they weren't anywhere near up to the
task.

Oh, come on! You're as bad as Bill about the 741. Of course it's not the
world's best hi-fi device, but I've used it in Sallen and Key filters
and as a straight audio amplifier up to 6 kHz without any serious
problems.

No, I wouldn't use it in an electric power meter if it had to meet the
tough specs that they normally have to.

 

[Ben Bradley]

Here are some 'hot' parts that I like using (mostly because they are
real cheap). Anybody got any favorites?

http://members.cox.net/berniekm/Hot_Parts.html

No one mentioned the 555? I admit I haven't used one in a lot of
years, but it's been quite popular.
For just one (old) application, the Apple ][ used a quad version
combined with software for a/d converters for game paddle position.

 

[N. Thornton]

Looks like John may be getting mixed-up with some other amp...

The 324 is often criticised for this. It can crossover distort
depending on how its used. Adding a pullup R on the output is a simple
way to put it into class A mode. However I've also used them without
that and had good results.


Regards, NT

 

[Jorge Omar]

Using discrete components?
Yes, I do!

Jorge

 

[Product developer]

Jim Thompson wrote...

Accckk, LM324 and active filters in the same sentence?!
Have you no shame?

Thanks,
- Win

whill_at_picovolt-dot-com

LM324? Is this guy stranded on an island with only a Radio Shack and a coconut tree?

 

[Costas Vlachos]

LM324? Is this guy stranded on an island with only a Radio Shack and a

coconut tree?


For those using the LM324, it's worth checking out the LT1014 from Linear
Technology. It's an expensive part, but much better than the LM324, pin
compatible, and a direct replacement in most cases. Typical offset voltage
of 50uV, up to 44V supply voltage, excellent CMRR/PSRR. A very fine part
IMHO for single-supply applications.

Costas
_________________________________________________
Costas Vlachos Email: [email protected]
SPAM-TRAPPED: Please remove "-X-" before replying

 

[Winfield Hill]

jdurban
wrote...

Winfield Hill wrote ...

LM324? Is this guy stranded on an island with only a
Radio Shack and a coconut tree?

It's been known to happen. In a strange city with
little time and only a Radio Shack at hand, it can
be amazing what one can accomplish.

Thanks,
- Win

whill_at_picovolt-dot-com

 

[Stefan Heinzmann]

jdurban
wrote...



It's been known to happen. In a strange city with
little time and only a Radio Shack at hand, it can
be amazing what one can accomplish.

And there are applications where cost is all that matters. Or does
anyone know of a quad opamp that is cheaper than the LM324?

There's a function generator of far-east brand on my bench that is built
using a fair number of 324s, discretes and CD4051s. It goes up to 10MHz,
although above 1MHz the results aren't very convincing. Still, kudos to
the designers for squeezing this out of such a poor device.

Cheers
Stefan

 

[DJ]

10K 1/4W 1%

dj

 

[N. Thornton]

about 'Singing the praises of the LM324', on Sat, 10 Jan 2004:

The LM324 is a basic spec part, but is very useful nonetheless. It
does a very wide range of jobs, and at a price thats just silly.

It does go above 6kHz, and well above. 6kHz is the max frequency at
which its rated to give full V swing out, due to slew rate. It does
20kHz quite happily, as long as your output magnitude _at that freq_
is well below full whack. It is thus good for audio.


Regards, NT

 

[Bill Sloman]

I read in sci.electronics.design that John Larkin <jjlarkin@highlandSNIP
techTHISnologyPLEASE.com> wrote (in <i9n000h8iroodgpf5d40rpu3dr5dkg6n36@
4ax.com>) about 'Singing the praises of the LM324', on Sat, 10 Jan 2004:
Oh, come on! You're as bad as Bill about the 741. Of course it's not the
world's best hi-fi device, but I've used it in Sallen and Key filters
and as a straight audio amplifier up to 6 kHz without any serious
problems.

No wonder you don't gag at the 741. But I do wonder what you *would*
rate as a "serious problem".

No, I wouldn't use it in an electric power meter if it had to meet the
tough specs that they normally have to.

There may be places in an electric power meter where the LM324 might
be useful - I've used them (in menial jobs) in quite high-tech
instruments.

 

[Jim Thompson]

LM324? Is this guy stranded on an island with only a Radio Shack and a coconut tree?

I was using LM324's in the 1977-1987 time frame. I had three basic
ICs that I used, LM324, LM339 and TL084, plus logic. I could build
*anything* ;-)

...Jim Thompson