[sdiy] IC Temperature

Mattias Rickardsson mr at analogue.org
Wed Aug 5 23:15:18 CEST 2020


On Tue, 4 Aug 2020 at 23:16, Mike Beauchamp <list at mikebeauchamp.com> wrote:

> On 8/3/20 8:11 AM, Mattias Rickardsson wrote:
> > ...
> > Btw, TL064s are hardly visible in the heat camera - they pull so little
> > current. Applying TL064 op-amps where noise & slewrate aren't critical
> > factors is an important trick in designs where power & heat & cost are.
> > ...
>
> Thanks Matthias, I appreciate the reply and reassurance. Interesting
> about the TL064, I've never heard of the chip before.


Oh, I thought the "precision" TL05x series were the unknown ones in the
family. :-) (Does anybody use them?) The TL06x are the low-power ones, and
the TL07x & TL08x are the twins separated at birth that nobody seems to
know if they are identical or not.


> It might be useful
> in some CV-summing and other non-audio sections, although taking a squiz
> at the datasheet it can only handle within +/-4V of each rail? (so +/-
> 8V on your case with the 12V bipolar supply?).


You must be referring to the Common Mode Voltage spec?
And it seems you're looking at the Recommended Operating Conditions, where
they for some reason exaggerate things from the Electrical Characteristics
section a bit.

Ordinary inverting op-amp stages have zero common mode voltage, so it's
normally not a problem. But in voltage followers it's important that the
common mode voltage doesn't reach close to the negative supply, or the
op-amp will show phase-reversal and possibly latch-up. Note though that
this is the same for TL07x, so you already have the issue there - check out
the datasheet! :-)


> It's easy enough to drop
> in on my PCB to see. I don't need to reduce the current and temperature
> now that I am no longer worried about it, but it would be nice to be a
> bit easier on the power supply. I am using TL074's pretty much
> everywhere to keep my BOM simple, and I have hundreds of them on-hand.
> But clearly they use a lot more power than I expected!
>

It's a bit annoying that op-amps often need much more current just to
function internally than they deliver to the outer world even at full force
and heavy load in our typical synth circuits. :-)

/mr
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