Low cost LM358 op-amp Audio Amplifier Circuit Diagram

This is the Low cost LM358 op-amp Audio Amplifier Circuit Diagram. The differential inputs give the amplifier excellent immunity to common-mode signals which are a common cause of amplifier instability. The dotted ground connection represents the wiring in a typical project illustrating how the ground sensing input can be connected to the ground at the source of the audio instead of at the amplifier where high currents are present.


Low cost LM358 op-amp Audio Amplifier Circuit Diagram

If the source is a power supply referenced signal then one of the amplifier inputs is connected to the positive supply. For example, an NPN common-emitter preamplifier may be added for very high gain and by connecting the differential inputs across the collector resistor instead of from collector to ground, destabilizing feedback via the power supply is greatly reduced.