Battery Powered (3V) Signal Detector.

I need to find/develop a circuit that runs off a 3V battery, uses very little current and detects the presence of an 8Khz sine wave looking signal. The signal runs from 10uv to 100mv. I need to detect when this signal is present and use this detection to generate an input to a microcontroller. The length of time that the signal is on needs to be accurate to 100usec.

Any help will be greatly appreciated. Thanks.

You could build a band-pass 80kHz active-filter and amp using micropower op amps such as this. After amplification you can rectify the signal and use it to trip a comparator to detect the presence of the signal.

"Very little current" does not mean much. If 5 mA does not bother you, this Fig. 7 shows capable of working at 3V.
---> http://www.datasheetcatalog.org/datasheets/105/233297_DS.pdf

Unsure if a LM567 would go that low also. Check its data sheet.

The length of time which signal needs to be on ? The one to detect or the detected output ?