How Do You Connect Vcc+ and Vcc- in a TL072 OpAmp Circuit?

[rusty009]

Ok, sorry for this basic question, I am currently designing a sallen-key high pass filter using a TL072 opAmp, with the schematic shown below,

This circuit is connected to a piezo trasnducer whose signal I wnat to amplify. I was wondering, what do I connect to the Vcc+ and Vcc- pins of the op amp ? Should I connect a battery to each pin or is one of them (Vcc-) the ground ? I am aware this is a very basic question but I was just wondering. Also, say I put 18 volts into the amplifier, will this turn my amplified signal into 18 volts ? Thanks.

 

[vk6kro]

The simplest arrangement is to have two batteries with one battery's positive and the other battery's negative going to the opamp and the other battery connections going to ground.

You can also use one battery and put a voltage divider across it to get a ground point.
Like this:
[PLAIN]http://dl.dropbox.com/u/4222062/LM324.PNG

However, this does take extra current from the battery for the voltage divider.

And it means the input signal must vary around the half-battery-voltage point (not around ground) or be capacity coupled into the opamp.

The output of the opamp is limited by the supply voltages, but it will be equal to the size of the input signal (usually measured in peak to peak volts), multiplied by the gain of the amplifier.

If this comes to more than the supply voltage, then the signal output will get distorted.

 

[berkeman]

And keep in mind that the TL074 style opamps do not let their inputs get very close to the rails. For +/-15V power supplies, the input common-mode range is only +/-11V. So you have to keep your inputs at least 4V away from the rails, which often limits your design...

http://www.datasheetcatalog.org/datasheet/texasinstruments/tl074.pdf

You can look at more modern (and more expensive...) CMOS opamps -- some let you get the inputs and output very close to the rails.