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Topic: op amp (Read 3765 times) previous topic - next topic

engelx

Hi!
i don't know wich op amp i can use (really i don't understand the op amps, and what they do XD)

the thing is... i'm trying to do a DAC to drive sounds from arduino to a speaker

the op amp used in the schematic is TS922, but i cant find that ones in my city (no, i cant buy it on internet for reasons)
my problem is... wich one i can use as substitute :s

i see that they (the store) have this (maybe they have others too)
TL081, TL082, TL084, LM741, LM3900, LM358, LM324, , LM311 , LM351 , LM339, OP07

thnx

btw i'm trying to do something like this...

CrossRoads

I think TL084 and maybe OP07 are lower noise op amps. Not sure if they are single supply capable, or if dual supplys are needed.
Search www.ti.com for spec sheets, do some reading.
Designing & building electrical circuits for over 25 years.  Screw Shield for Mega/Due/Uno,  Bobuino with ATMega1284P, & other '328P & '1284P creations & offerings at  my website.

engelx

CrossRoads: tnx :) the thing is, that i see the datasheets of the most... but i donĀ“t know what i looking for, i see a lot of values in which some looks more than TS922 than other (for example the TL082) but i really don't know if that values are the important ones for what i doing D: what i must look for?

CrossRoads

You want low noise inputs, single supply.
TL082 is 2 op amps, TL084 is same op amp but 4 in a package.
Designing & building electrical circuits for over 25 years.  Screw Shield for Mega/Due/Uno,  Bobuino with ATMega1284P, & other '328P & '1284P creations & offerings at  my website.

pito

#4
Jul 15, 2013, 09:14 pm Last Edit: Jul 15, 2013, 09:22 pm by pito Reason: 1
OP07 and TL084 are not good replacement for it. If you look at the TS992 datasheet (did you ??) the most important stuff for you is following to see:

Quote
TS922 .. rail-to-rail dual BiCMOS operational amplifiers optimized and fully specified for 3 V and 5 V operation ... high output currents which allow low-load impedances to be driven. The devices are stable for capacitive loads up to 500 pF


So you have to look for similar devices. Google "rail-to-rail high output current single supply"

engelx

CrossRoad: ok! now i know what i can start looking for...

pito: yeah XD i see the data sheep, but i think i was looking for the table of values... i was comparing numbers to the opthers op amp, thnx with that i think i can find something more specific :P ... i hope to find something i can buy in my city... D:!



CrossRoads

Yes, good call on the output current, I hadn't considered that.
Designing & building electrical circuits for over 25 years.  Screw Shield for Mega/Due/Uno,  Bobuino with ATMega1284P, & other '328P & '1284P creations & offerings at  my website.

Magician

You better to find LM386, not an OPA - just PA to drive a speaker.

engelx

ok! i have the LM386, i use as amplifier to the microphone... but how i use as low pass filter and current follower?

because what someone explain to me is that: it's going to sound pretty bad beacause the output signal isn't filtered, etc...


here what i'll get, and what i must have



i'm still not experimenting, but i'm try without the op amp and see how bad it sound...

CrossRoads

Need a low pass filter to take out the high frequency switching.
Can be simple R/C, or it could be an active filter, op-amp based, that would allow a sharper rolloff in frequency.
http://sim.okawa-denshi.jp/en/Fkeisan.htm
Designing & building electrical circuits for over 25 years.  Screw Shield for Mega/Due/Uno,  Bobuino with ATMega1284P, & other '328P & '1284P creations & offerings at  my website.

Magician

There is not much a filter, only 1-st order LPF. See 3k resistor and 0.01 uF cap? Put them in front of LM386.
Or you can borrow design from this page:
http://interface.khm.de/index.php/lab/experiments/arduino-dds-sinewave-generator/
That is about 5 times sharper compare to RC

engelx

i thought about to do that XD but i think that op amp was essencially for this! :P i'll try!

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