LM358 Audio Amplifier

Single-supply non-inverting op-amp drives a small speaker from a 3.5 mm jack.

Difficulty: Breadboard. Estimated build time: about 30 minutes. Estimated parts cost: about US$1.75. 11-part bill of materials with live supplier pricing. A single-supply audio amplifier using one half of an LM358 dual op-amp in a non-inverting configuration.