The biggest one I hit was some bad crossover distortion, which we "solved" = with a pullup resistor on the output. Some other info: https://www.electro-tech-online.com/threads/a-strange-problem-with-lm324.20= 769/ See post by Papabravo https://e2e.ti.com/support/amplifiers/etc_amplifiers__other_linear/f/18/t/6= 27753?LM324-Surprising-behavior-of-a-simple-amplifier " Also it should be mention that the LM324 family is unstable and may produ= ce a phase reversal if the input go under -300mV." https://www.edaboard.com/showthread.php?209783-LM324-opamp-gain-instability https://electronics.stackexchange.com/questions/341843/adding-a-resistor-to= -reduce-crossover-distortion-in-an-lm324-lm358 https://electronics.stackexchange.com/questions/341843/adding-a-resistor-to= -reduce-crossover-distortion-in-an-lm324-lm358/341853 https://www.edaboard.com/showthread.php?333332-HELP-OP-AMP-Using-LM324 -----Original Message----- From: piclist-bounces@mit.edu On Behalf Of Jason = White Sent: Tuesday, July 10, 2018 12:06 PM To: Microcontroller discussion list - Public. Subject: Re: [EE] LM124 Slew Rate vs Temperature? (-55C to 125C) Hello David, Can you outline the potential weaknesses of the LM324? I am perhaps a bit n= aive 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@backcount= ryaccess.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=20 > of them." > > I'd agree, it has "issues". > > > -----Original Message----- > From: piclist-bounces@mit.edu On Behalf Of=20 > Sean Breheny > Sent: Tuesday, July 10, 2018 9:09 AM > To: Microcontroller discussion list - Public. > 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=20 > the > LM324 family which is only really ever used now in either ultra cost=20 > sensitive devices or legacy designs. Except for cost, there are many=20 > op-amps which are better in every regard. > > I think you are right to be concerned. Slew rate depends on internal=20 > capacitances, resistances, and current magnitudes. All of those are=20 > temperature dependent AND manufacturing dependent. I would not be=20 > comfortable assuming this part can do 0.2V/us unless either the=20 > datasheet specified a minimum slew rate of more than that over all=20 > temperatures and manufacturing variation OR if the typical value were=20 > at least 10x the necessary value (2V/us). > > Sean > > > On Tue, Jul 10, 2018 at 10:29 AM, Jason White <=20 > 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=20 > > rate 0.2V/us). > > > > The LM124DT has a "typical" slew rate of 0.4V/us at 25C. A minimum=20 > > 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=20 > > might change over temperature. Additionally I'd like to get some=20 > > opinions as to whether 0.2V/us could be too fast for the LM124. > > > > Thanks, > > Jason White > > -- > > http://www.piclist.com/techref/piclist PIC/SX FAQ & list archive=20 > > View/change your membership options at=20 > > http://mailman.mit.edu/mailman/listinfo/piclist > > > -- > http://www.piclist.com/techref/piclist PIC/SX FAQ & list archive=20 > View/change your membership options at http://mailman.mit.edu/=20 > mailman/listinfo/piclist > > -- > http://www.piclist.com/techref/piclist PIC/SX FAQ & list archive=20 > View/change your membership options at=20 > http://mailman.mit.edu/mailman/listinfo/piclist > -- Jason White -- http://www.piclist.com/techref/piclist PIC/SX FAQ & list archive View/chang= e your membership options at http://mailman.mit.edu/mailman/listinfo/piclis= t --=20 http://www.piclist.com/techref/piclist PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist .