Hello, i wonder if anyone has an idea or mb a schematic of whats under the hood of a tda2030a...
I'm thinking can these chips (and others) be biased into class a by adding a current load between output and one of the supply rails like with opamps.
Any input is appreciated! Thank you.

 

I think you might be correct. They certainly run as class AB I believe under normal operation. I think their outputs are just a complimentary pair of power transistors. Did you see the datasheet? It may not show that much detail so really nobody can know for sure.

 

I would have thought not?, there's a specific reason that method works on one particular type of opamp - it's not going to work on a power amplifier, or indeed other opamps.

In any case, the 2030 is already a fairly decent performer, why do you want to alter it?.

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well there was a sell out thing at one of my local stores and they sold tda2030a with about 0.3$ so i bought a bag full of them . I was just curious if it can be done... thinking mb i could use it as a class a headphone amp or in tri-amping for those high freq.
Nigel i find it curious why u say that the method only works on one type of opamp... do u mean the lm324?
i found the internal schematic of the tda2040... could it be somehow similar?
in this case couldnt the output stage be forced to work single ended?

Attached Images

tda2040 internal.JPG (35.1 KB, 14 views)

 

You need to consider what the external resistor does on an LM324 - essentially it's a pullup resistor, so that provides the current rather than the other transistor. This is only possible because of the low output current it provides - for a power amp, assuming it could be done?, it would require a VERY low value resistor, which would destroy the bottom transistor.

But I'll say again, why not just use them 'as is' they are pretty respectable devices, 0.1% distortion at 8W into 8 ohms.

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You are right... but i can afford experimenting
and i think resistors can be replaced with an active load? i remember i've seen it done on opamps with some cascode with fets... if u keep the bias curent at bay could it still be dangerous for the device?
Thx for ur help!

 

The mod for the LM324 is to remove the excessive cross-over distortion in the chip, the problem doesn't apply to the TDA2030. I don't see how an active load would help?, it would only be worse than a resistor.

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I see well then its settled.. thanks a bunch!

 

Man, you got a good deal $0.3 each? Does he have anymore and will he ship them?

 

hmm i got'em from a store... dont know if they will ship but i live in Romania so shiping to US will probably cost more than the ics...
Cheers!

 

The fanatics at the headphones amplifier forum added a class-A load to the OPA2134 opamps they use, to reduce the 0.00008% distortion!!!

Attached Images

OPA2134 details.PNG (17.2 KB, 6 views)

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