Op amp for fairly high speed

John, The AD829 should do the job. What is your power supply voltage? What is your load impedance? With +/- 5V supplies and a 50 Ohm load, the nominal output voltage swing capability of the AD829 is only +/- 1.4V. Another problem may be that you don't know how to spell your first name :) Regards, Jon

I have +/- 12 and I've seen the output go to 10 V or so, but that was with the output going to a scope, not the equipment. I'm not too sure of the impedance; most of the gear is connected by 50 ohm coax. I may revert to an inverting config so I can have 50 ohm input impedance.

I'll work on the spellling,

jahn

Ok, so the maximum criteria is:

- 5us shortest rise/fall time (pretty slow as things go, FYI :)

- 10V (p-p?) output

- 100kHz maximum rate ?

10V in 5us is 2V/us slew rate. Even the lowly 741 does 5V/us, IIRC. (Oh nevermind- it's a tenth of that! Well, discrete circuits I've built easily handle this.) Well, the LM833 does >5V/us, anyway.

First of all, what is your signal, and what is your goal with it?

If you just want straightforward *amplification* of a trapezoidal wave (that is to say, square shaped pulses or whatever, but with sluggish rise and fall time slope), a reasonable speed op-amp wired for a gain of 10 or so will do it right there. If you want to *generate* the slopes, accurately, from a relatively square signal source, you need to look at slew-rate-limited amplifiers. There was a discussion on this a few months ago IIRC.

Tim

--
Deep Fryer: a very philosophical monk.
Website: http://webpages.charter.net/dawill/tmoranwms

John,

If you have the 50 Ohm termination, you just can't get +/-10V output swing out of the 829. Actually you can't get +/-10V at 2K if your power is +/-12 V, at least you will not be guaranteed to get it. You can see all this stuff well documented in the graphs of the 829. You would have to look into the compensation, choose the non-trivial one (I do not remember its name now, it is explained in the application text of the data sheet, basically a much lower cap than otherwise between compensate output and inverting input).

Dimiter

------------------------------------------------------ Dimiter Popoff Transgalactic Instruments

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P.S. I do love the 829, I have been using it since 1991 and still there is no better replacement for most of the applications I have designed it in.... :-).

jj wrote:

Yes, just amplification, and per Dimeter, I'm looking at adding a follower to drive a 50 ohm load. What is bugging me the most is the lack of linear amplification. It is almost like I have a comparator that puts out one of two levels depending on the gain (at the rail, or somewhere lower, jumping suddenly as the feedback value is changed).

Thanks for the advice.

John

Dimiter,

Thanks for the help. I'll look at a follower to drive the load.

John