Small Low-Voltage High Quality Audio Amplifier



LM386 is one of my favorite small audio amplifier integrated circuit chip. The LM386 is a power amplifier designed for use in low voltage consumer applications. The inputs are ground referenced while the output automatically biases to one-half the supply voltage. The gain is internally set to 20 to keep external part count low, but the addition of an external resistor and capacitor between pins 1 and 8 will increase the gain to any value from 20 to 200. The quiescent power drain is only 24 milliwatts when operating from a 6 volt supply, making the LM386 ideal for battery operation.

LM386 can be used in Applications such as: Portable tape player amplifiers, AM-FM radio amplifiers, Intercoms, Line drivers, TV sound systems, Ultrasonic drivers, Power converters, or Small servo drivers. The key features of this integrated circuit chips are:

  • Minimum external parts
  • Wide supply voltage range: 4V–12V or 5V–18V
  • Battery operation
  • Low quiescent current drain: 4mA
  • Voltage gains from 20 to 200
  • Ground referenced input
  • Low distortion: 0.2% (AV = 20, VS =6V,RL =8?,PO =
  • 125mW, f = 1kHz)
  • Available in 8 pin MSOP package
  • Self-centering output quiescent voltage

Figure 1. Minimum Parts LM386 Amplifier Circuit Schematic

Minimum component count can be implemented in circuit shown in figure 1. For higher gain, we just need to add few more parts as shown in figure 2.

Figure 2. Higher Gain LM386 Audio Amplifier Circuit

Finally, to make our amplifier boost the bass frequency range, the circuit can be constructed as shown in the schematic/diagram shown in Figure 3.

Figure 3. Bass-Boost LM386 Audio Amplifier Circuit

The output power of this amplifier is between 250 mW and 1000 mW, depending on the type used. For LM386N-1, LM386M-1, LM386MM, the suitable supply voltage is 6V, with loudspeaker impedance 8? can give total harmonics distortion about 10% at power output 250-325 mW. For LM386N-3, the power source voltage is 9V with speaker impedance 8? can give total 10% harmonic distortion at 500-700 mW output power. For LM386N-4, power supply voltage is 16V and with speaker impedance 32? gives 10% total harmonic distortion at 700-1000 mW output power.