op-amp suggestions - 20MHz, 30mA, hi-z output

You should be asking yourself, and answering, this question before you go off into a drug induced dreamland over the composite circuit configuration, bit head.

In article , Jim Thompson wrote: [...]

No, not you. The questions were aimed at the OP. I was partly pointing out that you were having to assume stuff that may not be true.

As for charge injection: it depends on how long the circuit has to recover.

That's correct, it's merely a muscular opamp, like I said.

Sorry Win, not AD815. I used that one a few years ago in a calibrator and it doesn't have tri-state unless my age-enfeebled mind is worse than I thought!

steve

Yes. "In the shutdown mode, the output looks like a 40pF capacitor and the supply current is typically 100uA." A nice part, I added it to my table. I like the LT1206CT7's TO-220 package, with its 5 C/W thermal resistance. One possible issue, it's a current-mode opamp.

part f_T Vsupply Iout slew tristate number manuf MHz max max V/us output? comments ------ ----- --- ----- ---- ---- ------- ------------ LT1206 LTC 120 36V 500mA 900 yes current mode CLC431 NSC 120 33V 60mA 2000 yes G = 2 min CLC411 NSC 200 36V 70mA 2300 yes +/-6V Vout max

And one huge advantage for the LT1206 over the CLC parts, it's not discontinued! In stock at DigiKey for $5.42 qty 25, $4.35 qty 1k. That's a pretty reasonable price.

Thanks for the suggestions but budget pricing for these is $30+ so doesn't meet the cheap requirement.

The LT1206 suggestion was a good one, $4.83 to buy off LT so should be cheaper in quantity. I should have thought to check LT. I did look at NSC and TI but couldn't get search to return anything useful (in budget and in spec).

My apologies to all for not replying earlier but as someone pointed out I am in UK and have to sleep sometimes, plus I pressed the wrong button (reply by email not post to newsgroup) so this is another day late.

I've got a discrete solution working now (well simulating anyway). A couple of transistors and unbuffered cmos gates as amplifier (was using those anyway). I expect I'll stick with that as it is the cheapest solution and one that is easy to simulate. BTW it is not quite the same as a Hi-Z op-amp but effectively a hi-z op-amp with dc offset (single side drive). I can live with that as I have tuned transformer output stage.

Thanks to all who replied (except the impolite one with the drug comment - why bother to post if all you can contribute is white noise!).

And there's the LT1207, which is a dual LT1206 in a 16-pin soic. BTW, both the LT1206 and LT1207 have thermal shutdown circuits.

In article , Winfield Hill wrote: [....]

Go back a level for the table.

The LT1206 also drives reactive loads, capacitive and inductive, without going silly. A lot of parts that drive capacitive loads ok have trouble with inductive loads.