The following PDF shows the TL431 used as an integrator in the feedback loop of a power supply:
How's that possible, when all the TL431 datasheets I've seen have the inverting input connected to the internal voltage reference, and the noninverting input brought out to a pin?
NM, it's because of the output transistor. Take the output from a pull up resistor and it inverts.
As the article suggests, just consider the TL431 as an op-amp, with the
+ve input internally connected to a voltage reference.I've seen other circuits using the TL431 as an integrator to maintain overall stability.
Incorrect! The TL431 is NOT an integrator, it is NOT used as an integrator, and NO SUCH THING is said in the article. Be VERY careful concerning the 431. The STM TS431, the National LMV431 the LM431, and the TL431 are all for the same purpose, but one seems to stand out as a variant on voltage referred to cathode or to anode. Better find out which does what and if the particular variant you are ACTUALLY using will even work for you...
Excited? Can be used as integrator, one of the app note circuits clearly has a cap between ref and cathode, feeding a Darlington to make a regulator.
It's cute ;) Wonderful. Ubiquitous. PCs wouldn't work without it, some PC power supplies use several! For example the mag-amps and SB5V.
Fairchild makes one too, FAN431! But tell us, which one is upside down? That could be handy.
Isn't that a bit like saying an op-amp isn't an integrator. It isn't but can be made one by placing a capacitor between the inverting input and the output.
I think you'll find adding a capacitor between the sense input and output turns the TL431 into an integrator, there's oodles of gain in the device to make a pretty good one as well.
Yep, I did it in all the GenRad portable tester switchers. ...Jim Thompson
Been years..i think it was the STM part.
Yes; an op-amp is NOT an integrator..only the full circuit is the integrator.
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