Interesting link

[Gus]

Something I found looking for something else
http://www.edn.com/design/components-and-packaging/4368741/Build-an-op-amp-with-three-discrete-transistors

Might be fun to try

[dwmorrin]

I've run across that article before.  Nearly every comment tears it up, pointing out over and over that it's not an op amp, the OL gain isn't a million, "why not just use an op amp?" etc...
It's less convenient to use 3 transistors than an op amp... and the main benefit of discrete op amps (from what I've read) is the ability to run them beyond the +/-15 (maybe up to +/-20) of typical op amps.
But maybe you were thinking, "hey, wonder if there's a cool fuzz pedal I can make out of that?" That's what I thought when I first saw it.  Never tried it though.  Putting it back on my "to breadboard" list.

[Gus]

I posted this because it is not a more perfect opamp like you can buy.  And guitar effect distortion is about generating distortion not being clean.

It is shown in an inverting opamp configuration.

It also is shown with 9VDC

So I thought I wonder how it might sound clipped.  Drop R1 to 10K for a gain of 100 from a perfect voltage source. 
Maybe drop R1 to 1K and drive this direct from a PASSIVE guitar or bass.  The passive guitar or bass is now part of the gain setting R2/(R1, C1 plus the RLC of the passive guitar/bass) along with the openloop gain.

D1 looks like it will add noise being a zener

[dwmorrin]

Totally agree about wondering about it as a guitar pedal.

From my limited knowledge of discrete transistor design, I see a 3 transistor amplifier with global shunt feedback, RC coupled.
So, from just a curiosity/knowledge-seeking stand point, is it "correct" to call this circuit "transistors in an inverting op amp configuration?"

I don't know where to look up "the official" op amp definition... but I think the ability to dc couple the signal is a requirement for the "operational" title.  This circuit could not be dc coupled... right?

Here's a cool breadboard discrete op amp:
http://www.allaboutcircuits.com/vol_6/chpt_5/17.html

[mac]

As a fuzz pedal looks interesting. I'll try it.

As an opamp I don't know. If you're looking for a discrete opamp I found this one,
http://www.sm0vpo.com/begin/opamp00.htm

mac