Op-amp differential amplifier

On a sunny day (Mon, 2 Mar 2015 04:33:35 -0800 (PST)) it happened Patrick Chung wrote in :

As a general statement that makes no sense whatsoever.

You really didn't expect it to?

Many decades ago this configuration was carelessly called a differential amplifier, a name that was originally applied to an entirely different kind of amplifier (no pun intended). But quickly the proper name for this configuration was arrived at long ago: Difference Amplifier.

Surely an argument that "a wider range of input signals" is possible with "opamps" cannot in general hold. However, difference amplifiers made in ICs employ laser-trimmed matched resistors, and benefit from reduced wiring capacitance, so they can in principle outperform discrete circuits. But they're not cheap, and sadly the parts offered don't cover the full range of requirements (for wide bandwidth, etc.) that we're likely to need. Precision matched resistor sets help to solve this problem, allowing for high-performance discrete circuits.

Your webpages need re-writing. Besides reviewing the scene, reading datasheets, etc., I suggest you wait for AoE-III to come out in a few weeks, and read the Difference Amplifier section in Chapter 5, Precision Circuits, before rewriting your pages. BTW, as long as you've brought up the issue, Chapter 8 shows several examples of discrete and hybrid designs out-performing ICs.

Chung is a spammer--he never answers anybody, just posts his announcements. SED is widely mirrored on the web, so it's one way to get traffic to his site.

Cheers

Phil Hobbs

These days we have the FDA, Fully Differential Amp:

I think the comment about wider range of input refer to those super high VCM jobs using precision matched large input attenuation ratios.

On a sunny day (Thu, 5 Mar 2015 09:11:36 -0800 (PST)) it happened snipped-for-privacy@gmail.com wrote in :

^^^^^^^ ??????

mm professional audio engineers...

OK, I have been using the CA3028 in the late sixties or was it early seventies.. diff in, diff out.

It is not buffered out,... OK

And the CA3020 had power output transistors, also diff out, was my audio output amp for a radio, goes to 8 MHz though.