TLC085 Op Amps

Big_Valven

Member
2007-12-09 6:27 am
Hi all, my first post on the forums and a question.

I am putting together my own car sound system and I am looking at designing a preamp for driving amplifiers and the like from the outputs of the rest of the circuit. I have found the following chips from TI:

http://focus.ti.com/docs/prod/folders/print/tlc085.html

I am particularly interested in these as they are single supply so easy to integrate in my current system, and high output (many car amps these days are capable of accepting up to 8 volts of input!) They also have a shutdown function which is important as it can integrate with the rest of my system's muting functions (avoiding pop and noise during power-up, shutdown and signal changeovers.)

A few application questions. How hard are these to build a circuit around? I am not extremely experienced with op-amps but would presume they are roughly similar to a traditional op-amp but with biasing circuitry built in to avoid external biasing when used with a single rail supply. Also, each op-amp has a + and - input but only a single output. I can only presume the - input is a reference or ground point when used in audio but not absolutely sure.

Finally, anyone who could point me in the right direction about any external componentry needed to get these running from a 12v supply (heavily filtered) will be infinitely rewarded :)

Thanks all,
Big_Valven
 
"Single supply" generally means the input common mode range reaches down to (or below) the negative supply rail, and the output voltage can get very close to the negative rail. Usually these are meant to be used in a +5V or +3.3V supply application. You'll still have to bias the inputs into the common mode range.

Otherwise they're generic op amps, very easy to design a circuit around. TI has some great downloadable books on op amp design.

Those are some interesting specs, and that family should do nicely for automotive applications. Be aware that the +12V in a car is generally +14V when running, and that it's a very noisy bus. Definitely put some overvoltage protection so you don't fry the chips - 16V max isn't a lot of margin for error.

I suggest the TLC084 instead because the '085 has a non-standard pinout.