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

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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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.
astroboy907 (author)  steveastrouk6 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...

Try it.

Steve
astroboy907 (author)  steveastrouk6 years ago
in bridge?
No,keep it simple

NachoMahma6 years ago
. According to the datasheet, a TDA2822 will output (Io) up to 1.5 A.
astroboy907 (author)  NachoMahma6 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....
astroboy907 (author)  astroboy9076 years ago
Also what would the output voltage be (so i can determine correct resistor value for leds)
. I dunno. Since the supply voltage is 15V, it has to be below that. Read the datasheets.
astroboy907 (author)  NachoMahma6 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 :)
astroboy907 (author)  astroboy9076 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 :) )

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