AD843 - pre/headphone amp

[lordearl]

I've read so many good things about this opamp, yet given it is so fussy, no-one seems to have designed an amplifier based solely around it.

Has anyone seen a decent circuit using this chip?

[gootee]

Here is the product page, at analog.com:

AD843 | 34 MHz, CBFET Fast Settling Op Amp | Military/Aerospace | Other Products | Analog Devices

Here is the datasheet:

http://www.analog.com/static/importe...eets/AD843.pdf

Maybe it's a little too "hot" for typical audio circuits, with its 10 ns rise time and 250 V/us slew rate. But I see no overriding reason that you couldn't try it, at least just to see what happens, if you pay some attention to the datasheet's circuit recommendations.

[stratus46]

Originally Posted by lordearl

I've read so many good things about this opamp, yet given it is so fussy, no-one seems to have designed an amplifier based solely around it.

Has anyone seen a decent circuit using this chip?

When I did video design I looked into this amp and while it was passable for standard definition, it won't cut it for hi def. Audio wise its a little noisy and a little low on drive current. The 'fussiness' has more to do with its speed. I.E. you'd have similar concerns with any 250 V/uS amp, not the 843 in particular.

You need good grounds and stiff power supplies when dealing in high speed. It's generally 'safer' to run somewhat lower impedances with high speed amplifiers. Feedback resistors in the 1-10K range rather than 30-50K. Ground plane PCBs are preferred rather than a ground 'trunk' snaking its way around the board.

There are opamps a little better tailored for audio than the 843 but by all means try it. It certainly isn't bad but then again I AM biased towards Analog Devices products.

G²

[Nisbeth]

Some notes: Notes on Audio Op-Amps


/U.

[Dr.EM]

Is such high bandwidth ever required for audio applications? Surely an audio specific op-amp (AD797, LM4562, even OPA2134) will give better performance in audio applications? The audio specific design of these op-amps gives them lower noise and THD whilst maintaining plenty adequate bandwidth.