Hello Denny, I've talked some more with the customer today and curiously the "effective" operating temperature range has been reduced to -40C to 70C. That makes my life quite a bit easier. I suspect I will still be sticking with 324 type part if I can. -Jason White On Tue, Jul 10, 2018 at 3:02 PM, Denny Esterline wrote: > Fair point - there's also the OPA211AID series that's "only" rated to 150= C > But even the $7-$8 a piece is far more dear than the $0.28 your budgeting= .. > > I don't know what you're building, or what market segment it has to sell > in, > but - to me at least - the temperature range you specified and the idea o= f > balking at $0.28 parts does _not_ belong in the same project. > > > > > > Personally, I found it quite amazing that there are parts rated to operat= e > above the melting temperature of solder... > > On Tue, Jul 10, 2018 at 11:14 AM, Jason White < > whitewaterssoftwareinfo@gmail.com> wrote: > > > Hello Denny, > > > > I didn't mention it but actually the effective operating temperature is > > "around ~110C" I am actually more concerned with the -55C operating > > specification. If what you say is true then the slew rate would slow at > low > > temperatures. > > > > I suppose I will have to reduce the peak-to-peak voltage of my 25kHz > > triangle wave to 1V to lower the slew rate requirement to ~1/10th the > rated > > slew rate. > > > > I like the specifications on the OPA211 but I suspect price ($77 per ch= ip > > vs $0.28/chip) may a limiting factor here. > > > > -Jason White > > > > On Tue, Jul 10, 2018 at 12:24 PM, Denny Esterline > > wrote: > > > > > Interesting question. Unfortunately all I have is wild speculation. > > > A brief glance at the datasheet shows a bipolar output stage. > > > In general, bipolar passes more current and has higher leakage at > > > elevated temperatures. Into a fixed load, I would expect that to > > > increase slew rate. > > > Part of the problem is that the load and all the other parameters > > > have temperature dependencies as well. The combined effect is > > > very unpredictable. Be fun to build a test fixture and measure > > > it though..... > > > > > > The other thing I noticed in the datasheet is that the part is spec'd > > > to an absolute maximum junction temperature of 125 C. Effectively > > > that means you cannot use it at an ambient temperature of 125 C > > > as it wouldn't be able to dissipate any heat. That may or may not be > > > a problem for you, depending on whether the 125C is a real spec > > > or a "marketing spec". > > > > > > I don't really know your application and design constraints, but a bi= t > of > > > research found this one: > > > http://www.ti.com/product/OPA211-HT > > > Which has a slew rate of 27V / uS and is specified to a high temp of > > > 210 C !!! (holy s*!t) > > > > > > > > > > > > > > > On Tue, Jul 10, 2018 at 7:29 AM, Jason White < > > > whitewaterssoftwareinfo@gmail.com> wrote: > > > > > > > In my current design the operating temperature range is rather larg= e: > > > -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 rat= e > > > > 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 mig= ht > > > > 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 > > > > -- > > > > http://www.piclist.com/techref/piclist PIC/SX FAQ & list archive > > > > View/change your membership options at > > > > http://mailman.mit.edu/mailman/listinfo/piclist > > > > > > > -- > > > http://www.piclist.com/techref/piclist PIC/SX FAQ & list archive > > > View/change your membership options at > > > http://mailman.mit.edu/mailman/listinfo/piclist > > > > > > > > > > > -- > > Jason White > > -- > > http://www.piclist.com/techref/piclist PIC/SX FAQ & list archive > > View/change your membership options at > > http://mailman.mit.edu/mailman/listinfo/piclist > > > -- > http://www.piclist.com/techref/piclist PIC/SX FAQ & list archive > View/change your membership options at > http://mailman.mit.edu/mailman/listinfo/piclist > --=20 Jason White --=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 .