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-   -   TDA7293 as output stage (http://www.diyaudio.com/forums/solid-state/137613-tda7293-output-stage.html)

lumanauw 30th January 2009 01:35 PM

TDA7293 as output stage
 
TDA7293 can be used as a stand alone buffer power amp (G=1). It can be pararelled too, without using ballast resistor for each chip.
Anybody has use this chip, only using the output section? For example for making non-global feedback power amp.

ashok 30th January 2009 01:56 PM

The application note says the output stage can be paralled with the first chip which would have nfb on it. That would bring all other paralled stages into the nfb loop.
They don't seem to mention the behaviour of the output stage on its own. Can it function normally without the input stage ?
Paralled output stages still use the input stage of the first chip !
Without the input stage does it still have dc current bias and how about the stability of the output dc level ?
Maybe it's on the block diagram but I don't have it in front of me right now so it's just a thought that occured to me .
Cheers.

lumanauw 30th January 2009 02:36 PM

2 Attachment(s)
The simplified schematic can be seen on it's family, TDA7294. But this chip cannot be used as a standing alone output stage. TDA7293 can.

It's interesting because the connection from the front stage to the power stage is only 1 line (pin 11). I would assume this single connection means that the output section can manage it's distortion by itself.

The output stage is not openloop. It has an opamp block (in the simplified diagram) that controls the output stage. But from the datasheet, it can work as a buffer, G=1

ashok 30th January 2009 02:51 PM

Yes the circuit does show more but does it show dc conditions completely ?
Has anyone actually checked this out ? Output stage conditions without any connection to the input stage or any other chip ?
It is an interesting idea.
I do have a TDA7293 but it's hard right now to check this out myself. Maybe by next week ! I have a wired TDA7294 which doesn't have this capability. A pity.
By the way TDA7294's are much easier to come. I've tried to get TDA7293's since middle of last year and still have not been able to get them locally. 7294's are available easily.
Is it the same globally ?

Cheers.

lumanauw 30th January 2009 04:18 PM

Yes, it's harder to find TDA7293 than TDA7294. TDA7293 is newer than TDA7294. I hope I can test it soon, whether it works as a power buffer or not. Not many power buffer (G=1) out there. BUF634 can only give 250mA. Other chipamps are design to have G=10x minimum.


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