Recommended · for beginners
What is an op amp? Operational Amplifier tutorial & super spy microphone circuit
Why people recommend it
An introduction to op-amps that builds a sensitive microphone amplifier, linked by beginners replicating the circuit for audio and sensor projects.
Watch for: not designed to drive an 8 ohm speaker
In their words
I found a video on youtube where the author amplified a heartbeat and his cat purring (link).
Dov on electronics.stackexchange.com, Dec 2012. CC BY-SA.
Here's the youtube video about the LM324 since it wouldn't let me post more than two links.
Technically Artistic on electronics.stackexchange.com, Jun 2015. CC BY-SA.