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TL431 as an audio amplifier fed by 1.2v?

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neazoi

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Hello, there are a few circuits on the net for the TL431 used as an audio amplifier. I wonder, is that possible for it to work also in low voltage 1.2-1.5V with reasonable gain, so that it can be combined with a TA7642?
Any ideas/schematics would be useful.
 

It has a minimum operating voltage of 2.5V so no, it can't be used on anything lower than that. Also note that 2.5V is the lowest voltage it can regulate at so it you are feeding audio into the reference pin, the output will not go below 2.5V, the most voltage you can get out of it is the difference between supply and 2.5V. It will only operate at low current so don't expect much volume.

Brian.
 
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    neazoi

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It has a minimum operating voltage of 2.5V so no, it can't be used on anything lower than that. Also note that 2.5V is the lowest voltage it can regulate at so it you are feeding audio into the reference pin, the output will not go below 2.5V, the most voltage you can get out of it is the difference between supply and 2.5V. It will only operate at low current so don't expect much volume.

Brian.

Thanks Brian.
 

Hi,

Hello, there are a few circuits on the net for the TL431 used as an audio amplifier.
Maybe because of April 1st. TL431 is a voltage reference.

For sure you may mistreat a shunt regulator as amplifier.
... with all it´s drawbacks..

By why not use a voltage reference as voltage reference and an audio amplifier as audio amplifier.
They both are designed and optimized for their purpose.

Klaus
 

Hi,


Maybe because of April 1st. TL431 is a voltage reference.

For sure you may mistreat a shunt regulator as amplifier.
... with all it´s drawbacks..

By why not use a voltage reference as voltage reference and an audio amplifier as audio amplifier.
They both are designed and optimized for their purpose.

Klaus

That's because it works great, if high gain is desired and if distortion is not an issue. It can amplify crystal sets in 8R speaker volume in a single stage, without oscillations and with a tiny footprint. No other reason, it just works!
 

At first, I also thought this was an April Fool's joke.

Alas no. The web is full of TL431s used as audio amps. There are even regenerative radio circuits.

I may even breadboard it one day, just out of sheer curiosity.
 
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    neazoi

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They do work, but rather like an op-amp that can't manage better than 2.5V from it's supply rails. LM317 works just as well and at higher power but is equally inefficient.

Brian.
 

Hi,

OK, high gain, but no output power.
What´s the maximum ouput voltage?
--> 100mA peak, in class A. means +/- 50mApeak (at best case, with "ideal" 0mV saturation voltage, at the edge to clipping)
at 8 Ohms --> +/- 0.4V peak. --> 20mW peak. --> 10mW sine audio power.

Some circuits show a 68 Ohms pullup at 6V. Thus the peak voltage (@8 Ohms speaker) can be 0.6V only (=5.6mW).
But they draw 80mA..which means 0.5W power consumtion.. continously. = 1% efficiency. independent of whether there is signal or not.
Not suitable for battery operations.

But I admit: it works.

***
It works, too: 230V AC input battery charger:
* Use a 230V incandescent lamp
* and a solar cell.
Simple circuit.

Klaus
 

TLV431 is an example of a lower voltage TL431 for 1.24V....have fun.

I admit I'm a TL431 fan have have used and concepted them into tons of things but was unaware audio was one of their applications.
 

They do work, but rather like an op-amp that can't manage better than 2.5V from it's supply rails. LM317 works just as well and at higher power but is equally inefficient.

Brian.

It would be interesting to see sometime a two stage AF amp with TL431 and LM317 :)
 

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