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Old 7th November 2013, 10:26 PM   #1
sohan is offline sohan  United States
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Default LME49810/11/30 without transistors?

Not sure if its a stupid question

Is there anyway to use any of those chips without any output transistors to build a 1 or 2w amp? or even lower? in class A?

looking for a minimal circuit with those chips with low wattage
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Old 7th November 2013, 11:38 PM   #2
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If you check the DS for the LME49810 you'll see that the minimum supply voltage is +/-20V and the typical output drive current is 60mA. A load that takes 60mA when driven 20V works out to be 333ohms and the power available will be about 600mW by my estimation. But if you went to the maximum supply you'd need a 1667ohm load and would get 2.4W.

So your answer is 'yes' but it seems unlikely you'd have any speakers/headphones in the impedance range 333-1667 ohms. If you used an output transformer you could potentially match to a lower impedance speaker but that rather detracts from the simplicity of the idea.

If your aim is low wattage with fewest components, there are cheaper solutions than these chips but you'd not get class A operation without adding more parts.

PS - not a stupid question at all, an interesting idea
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Last edited by abraxalito; 7th November 2013 at 11:43 PM. Reason: corrected rounding error
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Old 7th November 2013, 11:53 PM   #3
AJT is offline AJT  Philippines
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a parafeed amp, an output transformer to reflect 8 ohms to 1667 ohms load, a 100uf cap in series with the opt primary....
the best advertisement for a good audio design is the number of diy'ers wanting to build it after all the years....never the say so of so called gurus....
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