Hello David,

Can you outline the potential weaknesses of the LM324? I am perhaps a bit
naive with regards to the history and relative performance of this part.

-Jason White

On Tue, Jul 10, 2018 at 11:13 AM, Van Horn, David <
david.vanhorn@backcountryaccess.com> wrote:

> I don't know if it's true, but I like the comment attribuited to Bob Peas=
e:
> https://www.avrfreaks.net/forum/ultrasonic-sensors
> "National Semiconductors makes lots of good Op-Amps. The 324 isn't one of
> them."
>
> I'd agree, it has "issues".
>
>
> -----Original Message-----
> From: piclist-bounces@mit.edu <piclist-bounces@mit.edu> On Behalf Of Sean
> Breheny
> Sent: Tuesday, July 10, 2018 9:09 AM
> To: Microcontroller discussion list - Public. <piclist@mit.edu>
> Subject: Re: [EE] LM124 Slew Rate vs Temperature? (-55C to 125C)
>
> Hi Jason,
>
> Is there a reason for using such an ancient op-amp? This is part of the
> LM324 family which is only really ever used now in either ultra cost
> sensitive devices or legacy designs. Except for cost, there are many
> op-amps which are better in every regard.
>
> I think you are right to be concerned. Slew rate depends on internal
> capacitances, resistances, and current magnitudes. All of those are
> temperature dependent AND manufacturing dependent. I would not be
> comfortable assuming this part can do 0.2V/us unless either the datasheet
> specified a minimum slew rate of more than that over all temperatures and
> manufacturing variation OR if the typical value were at least 10x the
> necessary value (2V/us).
>
> Sean
>
>
> On Tue, Jul 10, 2018 at 10:29 AM, Jason White <
> whitewaterssoftwareinfo@gmail.com> wrote:
>
> > In my current design the operating temperature range is rather large:
> > -55C to 125C.
> >
> > I am planning on using the LM124DT from ST in an analog PWM circuit.
> > My design uses a 0.5 to 4.5v triangle wave at 25kHz (required slew
> > rate 0.2V/us).
> >
> > The LM124DT has a "typical" slew rate of 0.4V/us at 25C. A minimum
> > slew rate is not specified and slew is not specified at other
> temperatures.
> > Other manufacturers such as TI don't seem to specify this either.
> >
> > I would like to get an intuitive sense of how (or if) slew rate might
> > change over temperature. Additionally I'd like to get some opinions as
> > to whether 0.2V/us could be too fast for the LM124.
> >
> > Thanks,
> > Jason White
> > --
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Jason White
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