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How many LED's would a TDA2822 op-amp drive? Answered

Hey- trying to make led's light up to music, and i need to know if a tda2822 amp will light up ~15 leds (maybe more). i will be splitting them into high-mids- and lows. highs 3 leds, mids 4, and lows 8 leds. Sorry this question is so sketchy but i am writing this quickly. Power supply and necessary parts are not a problem.
Thanks :)

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steveastrouk

Best Answer 7 years ago

I'm going to make some estimates and reckon you run red leds, on a 6V supply, so you want a 180 Ohm -ish load resistor. That looks like a 300Ohm resistor to the supply. 10 LEDs, and you're at 30 Ohms load to your amp.

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astroboy907steveastrouk

Answer 7 years ago

Wow. this is ending up being harder than it looks

I will be running different colors of leds. they are all rated between 3 and 3.6v

I looked at the datasheets again, and the TDA2822 can power a 32 ohms impedance speaker at 300mw (with a 9v supply)
there is also this (but it might not have relevance)
Vo, Quiescent Output Voltage
Vs = 3V 1.2


and it gets to 2.7v with a 6v supply

i dont know if that would power it, cause if i use an led calculator (http://led.linear1.org/led.wiz)
it says the total array will dissipate some 950mw of power.. more than the 300mw of power with a 32ohm speaker (headphone?) impedance

i could run it in a bridge configuration and get 1w out for a 32ohm speaker with a 9v supply

it just gets more and more confusing...

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NachoMahma

7 years ago

. According to the datasheet, a TDA2822 will output (Io) up to 1.5 A.

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astroboy907NachoMahma

Answer 7 years ago

and assuming output voltage is ~3-10V... 1500ma / 20ma (per led)
wow. thats a lotta leds :) 75 at maximum
how about an LM386? (actually the part i am looking at is a LM386L, but i think the l is added) ** upon more research, the think this is the lead free part #


i cant seem to find output current in my datasheets....

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astroboy907astroboy907

Answer 7 years ago

Also what would the output voltage be (so i can determine correct resistor value for leds)

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NachoMahmaastroboy907

Answer 7 years ago

. I dunno. Since the supply voltage is 15V, it has to be below that. Read the datasheets.

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astroboy907NachoMahma

Answer 7 years ago

But since the leds will have resistance, wont they be more than 4 ohms? Im guessing impedance and resistance are two very different things...
Will probably try with a high-wattage variable resistor and play with it.
Thanks :)

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astroboy907astroboy907

Answer 7 years ago

It says in the datasheet for a LM386

"The inputs are ground referenced while the output automatically
biases to one-half the supply voltage."

I am buying the basic model, with less output

So if i hook it up to my 12v source (im going off of 12v instead of the maximum) i can get at least .25w of power going out (with a speaker impedance of 8 ohms)
i think im just going to try it... it outputs around 1/4 of a TDA2822, so it should run about 18 leds, more than i would need :)

please- if there is anything wrong with this please notify me, otherwise i will order parts soon- Thanks for putting up with my questions (and incorrect datasheet searching- i finally found something :) also my version for the 2822 says only 1Amp maximum. Not sure why that is but I'll live :) )

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steveastroukastroboy907

Answer 7 years ago

The output voltage depends on how "loud" you make it, and what impedance your leds present to the amp. It'll drop ~1V with an infinite load, so a 12V supply would be 11V on the load, and it'll drop to 3.5 volts on a 12V supply, with a 4 Ohm load.

Steve