protect arduino pins from high and negative voltages with single supply opamp

Using Arduino Audio
1

i am building a arduino based device which is powered by one single 9 volt batterie.
it receives analog and gate signals from synthesizers with its on board analog/digital convertors and digital pins and outputs signals via one mcp4921 dac and on board digital pins.
i want to buffer, protect and maybe scale signals of the dac and adc with LM358 single supply opamps.
i could find plenty of examples for audio modules with +/- supply's
and how to protect microcontroller inputs from negative and to high voltages but nothing for single supply devices.

thanks in advance for any help and hints

2

but nothing for single supply devices.

That is because on a single supply device running at the same voltage as the computer there is no voltage outside the range of the computer to be protected from.

However if you run the op amp of 9V and your arduuino is only 5V then you do need to protect the inputs. There are two ways to do it, a series resistor and rail clamping diodes, or a series resistor and a 5V1 zenner diode.

http://www.thebox.myzen.co.uk/Tutorial/Protection.html