OPA2156: slew rate stability across operating temperature range

Hi Bart,

I checked the original OPA2156 characterization data and it was accomplished at TA = 25°C only. The 40 V/us slew rate is specific to the conditions listed, VS = ±18 V, G = –1 V/V, with a 10-V step. That is a slew boosted condition.

In general for op amps, especially ones where their operating current remains relatively constant over temperature such as the OPA2156 the slew rate doesn't change radically over their operating temperature range. The OPA2156 operating current changes only a small amount across temperature (see datasheet Figure 39 - Quiescent Current vs Temperature) so the slew rate change should be small as well - a few percent at most.

Regards, Thomas

Precision Amplifiers Applications Engineering

Morning Bart, 

Tom is correct that there is rarely overtemp AC characterization done - including slew rate. Low tempco Icc certainly narrows the range of slew rate over temp., however at a fundamental level, there is a room temp range that is rarely specified - typical only has become standard. 

We used to try and deliver a lot more info on this and other AC specs in some of the BurrBrown high speed datasheets. I formatted those with columns of overtemp limits over  different temp ranges - that was a lot of sim work and fell out of favor over time. Those are slowly getting reformatted to simplify, but the OPA2677 still shows that approach. 

And then, is there any ATE data on slew rate at 25C outgoing screen? Most of the TI parts make no attempt at this, but most of the other vendors used a different ATE platform that offered this feature (including some of the older national high speed parts). I would consider this as not so much parametricly very accurate, just screening out broken parts. This of course is never attempted on the precision devices. 

And then, how you use slew rate in a design flow is a bit confusing. For instance, your external configuration plays a large role in whether slew limiting response will be encountered. Tried to step through some of these issues here - the next one higher speed devices (with true slew enhancement - I could not find in the OPA2156 any mention of slew enhancement ) will get into those for 2nd order edges. I am always checking what a linear response will ask for in peak dV/dT and then compare that to stated slew rate - or usually a guardbanded margin to that. For instance, once I estimate the peak output dV/dT for the application, I will screen parts to offer a min 1.5X that number - this is trying to account for how uncertain that number is over process and temp. Incidentally, trimmed supply current parts will have a tighter 25C slew range. 

https://www.planetanalog.com/separating-linear-from-slew-limited-performance-in-amplifiers-part-1-of-2-the-signal-sped-up-insight-14/