Opamp w/ Vsupply >36V

Here's something smilar, with an ISDN transformer to make 120 volts...

I'm using that one too (IRS2153D). I'll probably switch to the quicker one (IRS21531D) because it has 0.6 us dead time instead of 1.5 us. That will let me bump up the frequency and so halve the volt-seconds for a given output power.

The little ISDN transformers have leakage inductance below 0.1%.

Cheers

Phil Hobbs

Thanks.

What frequency do you drive it at?

Cheers

Phil Hobbs

Sure, as long as the LM317's output is enough to wake up the op amp. The output should be more or less an open circuit until the bias comes up, I think, so the 317's output follows its input till you start pulling current out of the resistor string or zener.

Cheers

Phil

Well what is this stuff about exceeding 36V??? Is it some kind of start-up overshoot?

I had a burn-in oven issue on a 5V part and 8V transorbs were fine. A lot depends on the chip design. Parts with large devices tend to do worse since the field created due to the excess voltage "seeks" a crystal defect. Lots of active area means more chances to find that defect. Most electromigration rules are generous enough that you don't see metal failure due to overvoltage. So the routing area doesn't count.

That part is bipolar on SOI. You would think the active circuitry would benefit from the insulator, but I have no first hand knowledge of that. [Usually a reversed bias diode is what fails in overvoltage.] But the part is cutting edge, so I can see the tolerances being tight.

Yeah I was going to add to the original thread that Apex opamp's need not apply :^) (too big and too expensive) There's that nice little LTC6090 that Fred Bartoli pointed to. (I should order some of them, to replace an Apex part.)

George H.

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able bias. The LM317's had too much drift and so I've now got a 10 Volt re ference gained up to 30V.

p overshoot?

Well I'm not exceeding 36 V. Just feeling that the design is a bit tight.. 30 Volt out with ~2V of head room at the top and the minus supply 2V below ground... And then worrying about the variation in parts. If I had, say 4

George H.

Hi George

Ask John Larkin if he can "dig" the schematic up again:

/Glenn

pushing the 36V supply limit and I?m a little worried. So I went looki ng for a similar opamp but with a bit more headroom.

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Hmm that link (whatever it is) doesn't work for me. But JL already posted a number of opamps. George H.

I think it was John's photo-MOS totem pole idea.

Cheers

Phil Hobbs

The FTP thing didn't work well, so I'm using Dropbox now. Here's the HV amp idea:

I actually did it once, for the atom probe project, and it worked fine.

What do you do with FB?

Whatever you like. What you do with feedback is application dependant.

Oh, those optos really deserve b-e resistors. That reduces CTR but increases speed and breakdown voltage.

Of course, but how? You must have had an equally clever way to isolate it.

Flooby Dust ?:-} ...Jim Thompson