Here is an interesting op-amp circuit which - it is claimed - can be used to help your sound card last longer.

Here is the idea behind this circuit.  First of all, it seems to be an absolutely useless circuit because the output is - theoretically - exactly equal to the input.  What could you use a circuit like that for?  Here's the answer.

• You want to use the sound card function generator.
• You don't want to fry your sound card.
• You use this circuit.
• Instead, if things don't pan out, you fry an op-amp.
• The op-amp costs around 25 cents.
• The sound card costs much more than that.
• If anything is going to be fried, it's better that it's an op-amp.

• Construct the circuit above.
• Determine whether or not the output voltage equals the input voltage.
• Determine if the sound card output voltage drops when the circuit is attached.
• Determine the output resistance (TEC resistance) of the circuit.
• In your report comment on whether eliminating the possibility of frying the sound card is the only interesting aspect of this circuit.