I need a voltage sensing window comparator opamp subsitute for TLC272. Would you please advise an alternative. An LM386 will provide input from an electret mic. The application is a noise monitor for our elementary school cafeteria. Thank you.

 

The TLC272 is a CMOS operational amplifier that has a common mode input range to the negative rail.

Post your schematic as it now exists.

You would likely be better off going to a comparator (like a commonly available LM339) and add hysteresis.

 

I am inexperienced and am looking at a Forrest Mims circuit that uses the TLC272 that activates three led's, depending upon voltage input. I have been working at this project daily for two months without success. The voltage senser circuit is a new tack. I am hoping the output can be used as digital input to an Arduino for further data processing. Analog readings from an LM386 ("Physical Computing") are unstable, even after hysterisis, because the range is too narrow. Hopefully, the window comparator will be easier to calibrate. Any advise is very much appreciated.

 

Well, right now we have NOTHING to go on other than a very general description.

Having a schematic handy of how things are now, will help to determine in which direction you need to go in.

 

This is the circuit I would like to use with the voltage comparator:

http://www.tigoe.net/pcomp/code/category/arduinowiring/208

I should have been able to use the output of this circuit to enable LED's from the Arduino but failed time and again as the led's would jump about whenever values are close.

 

The LM386 circuit is missing some of the important parts recommended on the datasheet of the LM386.
There is supposed to be a 10 ohms resistor in series with a 0.05uF (0.047uf) capacitor at the output to ground to prevent oscillation.
There is supposed to be a supply bypass capacitor at the IC.

The author does not know what he is talking about. The output voltage of the LM386 is already +2.5V and the two 100k resistors do nothing. The +2.5V is changed by the signal to +1V to +4V.