I'd like to get audio (specifically a line out) from a Cortex-M4 10 bit DAC (LPC-4337). The dev board I'm using already has a 470 Ohm resistor in series with the DAC. Since I've never worked with sound I'll appreciate any advice on the following:

1) How should I bias the 0-3.3v DAC output to an AC wave centered at 0v?

2) Should I block DC with a polarized series capacitor at the output?

3) How could I electrically protect the mcu DAC pin?

I only have 5v, 3v3 and ground available, no negative voltage.

I suspect a single supply, unity gain op-amp with bias will do, but I've never used an op-amp for this application. An example will be very appreciated.

Thanks in advance!

  • 1
    \$\begingroup\$ The only issue really is how close your DAC output goes to the 0V rail. If it drops down there, use a rail to rail input and output op amp like the TLV2371. Configure it as a unity gain non inverting buffer- that is, positive input to DAC via the resistor, negative input connected directly to the op amp's output (full negative feedback), then whack a DC blocking capacitor on the output and take your own output from that. Job done. You don't need to bias the op amp. No reason to "protect" the MCU either, the op amp input is very high impedance. \$\endgroup\$ – Ian Bland Apr 30 '18 at 19:47
  • \$\begingroup\$ Is this question still relevant? \$\endgroup\$ – Harry Svensson May 28 '18 at 21:11

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