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: -55=
C
> 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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