Hi, We are trying here to detect and amplify EMG-sginals 65-150 Hz, the detection and amplification is working good. The problem we have is envelope detector and schmitt trigger, to detect and A/D conversion. Our Lower threshold= 0.2V Upper threshold= 0.8V everything in between is none of interest. We are using uA741 OpAMp, diode: 1N4148. P.S. envelope detector is working as a standalone but not when it's connected to schmitt trigger. See the attachment pic. I also attached the whole circuit that you can simulate on www.docircuits.com. All help are appreciated. Thank you in advanced.