Now I show the perfect low distortion sinewaves at the output of my circuit
3 problems with that.
- Heartbeats are not perfect sinewaves; and certainly not 1kHz sinwaves. They are a mismash of frequencies ranging between ~10Hz and ~1000Hz; all mixed together.
- Your graphs -- I assume -- are the output waveforms; showing roughly 7V peak to peak; but the input stages of the phone are expecting the input from an unamplified electret mic. That's why everything is being clipped. Your circuit is designed to drive the 8 or 16 ohm input of a pair of headphones or speakers, not the input stages of smartphones.
- Smart phones need to see an impedance of 800+ ohms(*)to recognise that an external mic is plugged in.
Further evidence:
Last edited: