Electret Microphone & PGA or Differential Amplifier?

Discussion in 'General Electronics Chat' started by Berek, Jun 18, 2011.

  1. Berek

    Thread Starter New Member

    Jun 18, 2011
    Hi guys, I have the next problem and I hope some of you could help me in this or give me some advice! (excuse my english btw)

    I'm working in a digital stethoscope with the dsPIC30F, for the sensor I'm going to use an electret microphone. For the first amplification I was thinking about using a PGA (MCP6SX from Microchip).

    The thing about stethoscopes is that you need to get only the heart sounds (those are in the frequencies of 50 - 200 Hz.), isolate the ambient noise, and try to get the mic in the bell.

    According to the application notes of the Microchip and of Instrumentation Electronics at a Juncture, the advantages of using the PGA is that you get the possibility of using more sensors while reducing hardware. However, this is for local sensing.

    For remote sensing, they suggest to use a differential amplifier, for the high CMRR or an instrumentation amplifier

    About the remote or local sensor, they say this:

    The thing is that I'm going to use the mic in a separate PCB that is with the bell of the stethoscope in a distance of 15-30 cm of the main PCB (with the power supply)

    So I'm not really sure what should be the best component for reducing the noise in this part, the PGA or using a differential amplifier/IA for the high CMRR?

    After this first phase I will use an anti-aliasing filter for the A/D conversion.

    Any other ideas or suggestions for reducing the noise?