OPA2228 what can it be used for

[Nordic]

I made the mistake of ordering some opa2228 chips in stead of opa2227, which is unity stable and therefore much easier to integrate.

Its not a bad chip, and if I understood the application docs, TI suggests using opa2227 for input impedance of under 10k, opa2228 from 10k to 100k, and opa2132 above that. SO, its simply a matter of horses for courses I guess.

Anyhow, I hate to let stuff go to waste, so I tried the chip in my cmoy, but it sounded awefully thin. Then I saw in the datasheet is a circuit for 2x gain (ps how do I convert that to db?) and one for 1/2 x gain (dunno what one would do with that).

I build the 2x gain circuit and it sounds very smooth very likeable.

I just tested with headphones but it didn't play terribly loudly. Possibly due to slightly under power battery I used to test it with... Oh well datasheet says it works fine vrom 5V upwards.. I suppose fine for other things, less fine for audio...

Can I put 2 of these 2x gain stages in series for 4x gain, or would that still not be worth it as a preamp stage for a GC?. My main source puts out nearly 2V full scale so I have gain to burn I think...

What would the synergy be like combining it with a valve based cathode follower as output stage.?

[lineup]

OPA2227 OPA2228 OPA227 OPA228 OPA4227 OPA4228
are variants of the same OP amp circuit.
High Precision, Low Noise Operational Amplifiers

they are all excellent for audio
-------------

OPA2228 is a dual of OPA228.
As you say, unity gain stable variant.
This means you can use it for gain= +1 or -1 and any other normal gain you like,
without adding any compemsation caps for stability.

Just like any normal Op-Amp.
Like OPA2134 or whatever.

You can use each one of the two for x4 or x10, if you like.
So getting 2 channel stereo left-right preamplifier with your desired needed gain.
As both channels are in same package, you can get preamp very compact at a small PCB.

These Op-Amps are so good, you need a well regulated supply
for utilizing best performance.
LM317 + LM337, as usual for Op-amps will do very well.
High CMRR = 120dB!!!
Which tells us this device will suppress ripple & noise from power supply to a very high degree.


You may use these chips for most anything within highest quality hifi audio.

Congratulations, Nordic.
Audio Op-amps do not come very much better than this.
Than this OPA circuit:
OPA2227 OPA2228 OPA227 OPA228 OPA4227 OPA4228
Product Page, info and datasheet
at Texas Instruments
http://focus.ti.com/docs/prod/folder...t/opa2228.html


lineup

[Nordic]

Thanks, so its not just my imagination, it was much more pleasant than opa2132/4

[Dominique]

Hi Nordic,

Your mentioned Opa 2134 (which has a fet input) has a higher input impedance than Opa2228, but I guess that will only be an advantage in a few cases...

The OPA228 could be externally compensated for gains lower than 10, but it's only a hint for the future, I wouldn't really do that 'cause it's already available as OPA227.
I like these chips a lot, they're very good performance, as lineup stated. Also, whenever I switched several op-amps in the same circuit, they were always among the best behaving, so they're rather easy to use!

Cheers,
Dominique