Monday, October 12, 2009

LM386 circuit audio amplifier

LM386 circuit audio amplifier

The LM386 circuit is a audio amplifier designed for use in low voltage consumer applications. 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 inputs are ground referenced while the output automatically biases to one-half the supply voltage. The quiescent power drain is only 24 milliwatts when operating from a 6 volt supply, making the LM386 ideal for battery operation.

LM386 circuit features

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

LM386 circuit applications

  • AM-FM radio amplifiers
  • Portable tape player amplifiers
  • Intercoms
  • TV sound systems
  • Line drivers
  • Ultrasonic drivers
  • Small servo drivers
  • Power converters

LM 386 series output power (Pout)

  • LM386N-1, LM386M-1 at VS = 6V, RL = 8ohms, THD = 10% is 250-325 mW
  • LM386N-3 at VS = 9V, RL = 8ohms, THD = 10% is 500-700 mW
  • LM386N-4 at VS = 16V, RL = 32ohms, THD = 10% is 700-1000 mW.

LM 386 amp circuit 20dB gain

LM386 Audio Amplifier with Gain = 20 and minimum part count.

LM386 audio amp 50dB gain

LM386 amplifier 200dB gain

LM 386 bass boost circuit

To make the LM 386 a more versatile audio amplifier, 2 pins ( pin 1 and 8 ) are provided for gain control. With pins 1 and 8 open the internal 1.35k resistor sets the gain at 20 (26 dB). If a capacitor is placed between pin 1-8, bypassing the built-in 1.35k resistor, the gain will go up to 200.

If a resistor is placed in series with the capacitor, the gain can be set to any value from 20 to 200. Gain control can also be done by capacitively coupling a resistor or FET transistor from pin 1 to the ground.


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