[sdiy] Op amp slew in audio circuits - sims vs. real life

[Neil Johnson]

Hi Justin,

> I'm assuming most of us throw the TL072 or similar at most of our audio
> circuit op-amp requirements right?

For general non-critical spots then yes the TL072 is a good go-to
op-amp.  The one thing it is good at is price :)

> Can any of you give some examples of where you specified an op amp with
> better/faster slew specs because standard op-amps weren't fast enough?

There's no such thing as a "standard" op-amp.  You can classify them
into groups, but even then those groups change.  Some time ago the 741
would have been the go-to standard op-amp.

You generally choose a fast op-amp if you need lots of gain and/or
wide bandwidth.  Then you're into video bandwidth op-amps, and heading
off into current-feedback op-amps.

> Asking because I'm working on a pulse output circuit (frequency up to 20KHz)
> that I'd like to shave every last µSec out of in order to get the sharpest
> response

Ah, so this is NOT an op-amp question, but an output driver question.
What are the signal levels involved?  If you just want a fast output
driver then grab a hex buffer or inverter and wire them up in parallel
- that'll get you nanosecond transition times.  CMOS will get you the
most dynamic range, either 0-15V or for bipolar use a couple of
voltage regulators to give you +/-5V.

Neil
--
http://www.njohnson.co.uk