How to Make a Simple Audio Amplifier

Operational amplifier integrated circuits come in an 8-pin package similar to these microchips.

Audio amplifiers are used to amplify sound waves that have been converted into electrical signals. An audio amplifier must amplify the input signal without introducing signal distortion.

One simple type of audio amplifier can be constructed using an integrated circuit called an operational amplifier. An operational amplifier (also known as an "op-amp") serves as the active component in the audio amplifier circuit.

Things You'll Need

• LM-158 operational amplifier
• One 6V battery
• One 5KΩ resistor
• One 1KΩ resistor
• Electrical wire
• Electrical pliers
• Electronic (rosin core) solder
• Soldering iron

Instructions

1. Cut five lengths of wire, and strip 1/2 inch of insulation from the ends of each wire. Twist together one of the leads from the 5KΩ resistor with one end of the first wire, and solder the twisted wire pair to the op-amp output pin (pin 1).

2. Twist together the free lead on the 5KΩ resistor to one of the leads on the 1KΩ resistor, and solder this wire pair to the op-amp inverting input (pin 2). Solder one end of the third wire to the non-inverting input (pin 3).

3. Solder one end of the fourth wire to the "V+" input pin (pin 8) on the op-amp. Attach the other end of the fourth wire to the positive battery terminal. Solder one end of the fifth wire to the "GND" pin (pin 4) on the op-amp. Twist together the free ends of the third and fifth wires, and attach the twisted wire pair to the negative battery terminal.

4. Attach the audio input source to the free lead of the 1KΩ resistor, and attach the output device (such as a speaker) to the free end of the first wire.

References

• Georgia State University: Op-Amp Varieties
• National Semiconductor: LM158/LM258/LM358/LM2904 Low Power Dual Operational Amplifiers
• Electronic Devices; Thomas Floyd; 1996

Resources

• Read this Article in Spanish