How to Build a Low Power Audio Amplifier

Operational amplifier integrated circuits are packaged in dual-inline packaging, such as these microchips.

Audio amplifiers are used to increase the power of an audio AC signal. When amplifying the input signal, it is important that the amplifier does not introduce distortion into the output signal. This can be a challenge in a low-power application, because some efficient amplifier circuits, such as the class-B amplifier, are prone to crossover distortion.



One way to create a low-power amplifier circuit is to use an audio-quality operational amplifier circuit. An operational amplifier integrated circuit -- or "op-amp" for short -- may be used with a low-power DC power supply and provides a high-fidelity output signal.

Things You'll Need

• One LM158 operational amplifier integrated circuit
• One 10-kiloohm resistor
• One 1-kiloohm resistor
• Electrical wire
• Electrical pliers
• Electronic solder
• Soldering iron
• Two ring terminals
• Six-volt DC power supply

Instructions

1. Cut five pieces of wire, and strip 1/2-inch of insulation from each wire end. Place one of the ring terminals over one end of the first wire, and solder the terminal to the wire. Place the other ring terminal over one end of the second wire, and solder the wire to the terminal.

2. Twist together one of the leads from the 10-kiloohm resistor together jointly with the output terminal on the op-amp, and with the free end of the first wire. Solder this connection.

3. Twist together the free lead from the 10-kiloohm resistor together jointly with the op-amp inverting input terminal, and with one of the leads from the 1-kiloohm resistor. Solder the electrical connection.

4. Twist together the free end of the second wire with the op-amp non-inverting input terminal, and solder the connection.

5. Solder one end of the third wire with the op-amp "V+" terminal. Solder one end of the fourth wire to the op-amp "GND" terminal.

6. Twist together one end of the fifth wire with the free end of the 1-kiloohm resistor, and solder the connection. Twist together the free ends of the fourth and fifth wires, and attach the wire pair to the negative lead on the power supply. Attach the free end of the third wire to the positive lead on the power supply.

Tips & Warnings

• The ring terminal at the end of the second wire serves as the input lead. The ring terminal at the end of the first wire is the output lead.

• Check the op-amp schematic to determine the op-amp terminal lead assignments.

References

• Georgia State University: Op-Amp Varieties
• National Semiconductor: LM158/LM258/LM358/LM2904 Low Power Dual Operational Amplifiers