SNAS545C May 2004  – May 2017 LM386

PRODUCTION DATA. 

  1. Features
  2. Applications
  3. Description
  4. Revision History
  5. Pin Configuration and Functions
  6. Specifications
    1. 6.1Absolute Maximum Ratings
    2. 6.2ESD Ratings
    3. 6.3Recommended Operating Conditions
    4. 6.4Thermal Information
    5. 6.5Electrical Characteristics
    6. 6.6Typical Characteristics
  7. Parameter Measurement Information
  8. Detailed Description
    1. 8.1Overview
    2. 8.2Functional Block Diagram
    3. 8.3Feature Description
    4. 8.4Device Functional Modes
  9. Application and Implementation
    1. 9.1Application Information
    2. 9.2Typical Application
      1. 9.2.1LM386 with Gain = 20
        1. 9.2.1.1Design Requirements
        2. 9.2.1.2Detailed Design Procedure
          1. 9.2.1.2.1Gain Control
          2. 9.2.1.2.2Input Biasing
        3. 9.2.1.3Application Curve
      2. 9.2.2LM386 with Gain = 200
        1. 9.2.2.1Design Requirements
        2. 9.2.2.2Detailed Design Procedure
        3. 9.2.2.3Application Curve
      3. 9.2.3LM386 with Gain = 50
        1. 9.2.3.1Design Requirements
        2. 9.2.3.2Detailed Design Procedure
        3. 9.2.3.3Application Curve
      4. 9.2.4Low Distortion Power Wienbridge Oscillator
        1. 9.2.4.1Design Requirements
        2. 9.2.4.2Detailed Design Procedure
        3. 9.2.4.3Application Curve
      5. 9.2.5LM386 with Bass Boost
        1. 9.2.5.1Design Requirements
        2. 9.2.5.2Detailed Design Procedure
        3. 9.2.5.3Application Curve
      6. 9.2.6Square Wave Oscillator
        1. 9.2.6.1Detailed Design Procedure
        2. 9.2.6.2Application Curve
      7. 9.2.7AM Radio Power Amplifier
        1. 9.2.7.1Design Requirements
        2. 9.2.7.2Detailed Design Procedure
        3. 9.2.7.3Application Curve
  10. 10Power Supply Recommendations
  11. 11Layout
    1. 11.1Layout Guidelines
    2. 11.2Layout Examples
  12. 12Device and Documentation Support
    1. 12.1Device Support
      1. 12.1.1Development Support
    2. 12.2Documentation Support
    3. 12.3Related Links
    4. 12.4Receiving Notification of Documentation Updates
    5. 12.5Community Resources
    6. 12.6Trademarks
    7. 12.7Electrostatic Discharge Caution
    8. 12.8Glossary
  13. 13Mechanical, Packaging, and Orderable Information

Package Options

Refer to the PDF data sheet for device specific package drawings

Mechanical Data (Package|Pins)
  • D|8
  • P|8
  • DGK|8
Orderable Information

Application and Implementation

NOTE

Information in the following applications sections is not part of the TI component specification, and TI does not warrant its accuracy or completeness. TI’s customers are responsible for determining suitability of components for their purposes. Customers should validate and test their design implementation to confirm system functionality.

Application Information

Below are shown different setups that show how the LM386 can be implemented in a variety of applications.

Typical Application

LM386 with Gain = 20

Figure 10 shows the minimum part count application that can be implemented using LM386. Its gain is internally set to 20.

LM386 lm386_typapp1.gif Figure 10. LM386 with Gain = 20

Design Requirements

Table 1. Design Parameters

DESIGN PARAMETEREXAMPLE VALUE
Load Impedance4 Ω to 32 Ω
Supply Voltage5 V to 12 V

Detailed Design Procedure

Gain Control

To make the LM386 a more versatile amplifier, two pins (1 and 8) are provided for gain control. With pins 1 and 8 open the 1.35-kΩ resistor sets the gain at 20 (26 dB). If a capacitor is put from pin 1 to 8, bypassing the 1.35-kΩ resistor, the gain will go up to 200 (46 dB). 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) from pin 1 to ground.

Additional external components can be placed in parallel with the internal feedback resistors to tailor the gain and frequency response for individual applications. For example, we can compensate poor speaker bass response by frequency shaping the feedback path. This is done with a series RC from pin 1 to 5 (paralleling the internal
15-kΩ resistor). For 6 dB effective bass boost: R ~= 15 kΩ, the lowest value for good stable operation is R = 10 kΩ if pin 8 is open. If pins 1 and 8 are bypassed then R as low as 2 kΩ can be used. This restriction is because the amplifier is only compensated for closed-loop gains greater than 9.

Input Biasing

The schematic shows that both inputs are biased to ground with a 50 kΩ resistor. The base current of the input transistors is about 250 nA, so the inputs are at about 12.5 mV when left open. If the dc source resistance driving the LM386 is higher than 250 kΩ it will contribute very little additional offset (about 2.5 mV at the input, 50 mV at the output). If the dc source resistance is less than 10 kΩ, then shorting the unused input to ground will keep the offset low (about 2.5 mV at the input, 50 mV at the output). For dc source resistances between these values we can eliminate excess offset by putting a resistor from the unused input to ground, equal in value to the dc source resistance. Of course all offset problems are eliminated if the input is capacitively coupled.

When using the LM386 with higher gains (bypassing the 1.35 kΩ resistor between pins 1 and 8) it is necessary to bypass the unused input, preventing degradation of gain and possible instabilities. This is done with a 0.1 μF capacitor or a short to ground depending on the dc source resistance on the driven input.

Application Curve

LM386 lm386_d001.gif
Figure 11. Supply Current vs Supply Voltage

LM386 with Gain = 200

LM386 lm386_typapp2.gif Figure 12. LM386 with Gain = 200

Design Requirements

Table 2. Design Parameters

DESIGN PARAMETEREXAMPLE VALUE
Load Impedance4 Ω to 32 Ω
Supply Voltage5 V to 12 V

Detailed Design Procedure

The Detailed Design Procedure can be found in the Detailed Design Procedure section.

Application Curve

LM386 lm386_d001.gif
Figure 13. Supply Current vs Supply Voltage

LM386 with Gain = 50

LM386 lm386_typapp3.gif Figure 14. LM386 with Gain = 50

Design Requirements

Table 3. Design Parameters

DESIGN PARAMETEREXAMPLE VALUE
Load Impedance4 Ω to 32 Ω
Supply Voltage5 V to 12 V

Detailed Design Procedure

The Detailed Design Procedure can be found in the Detailed Design Procedure section.

Application Curve

LM386 lm386_d001.gif
Figure 15. Supply Current vs Supply Voltage

Low Distortion Power Wienbridge Oscillator

LM386 lm386_typapp4.gif Figure 16. Low Distortion Power Wienbridge Oscillator

Design Requirements

Table 4. Design Parameters

DESIGN PARAMETEREXAMPLE VALUE
Load Impedance4 Ω to 32 Ω
Supply Voltage5 V to 12 V

Detailed Design Procedure

The Detailed Design Procedure can be found in the Detailed Design Procedure section.

Application Curve

LM386 lm386_d001.gif
Figure 17. Supply Current vs Supply Voltage

LM386 with Bass Boost

LM386 lm386_typapp5.gif Figure 18. LM386 with Bass Boost

Design Requirements

Table 5. Design Parameters

DESIGN PARAMETEREXAMPLE VALUE
Load Impedance4 Ω to 32 Ω
Supply Voltage5 V to 12 V

Detailed Design Procedure

The Detailed Design Procedure can be found in the Detailed Design Procedure section.

Application Curve

LM386 lm386_d010.gif
Figure 19. Voltage Gain vs Frequency

Square Wave Oscillator

LM386 lm386_typapp6.gif Figure 20. Square Wave Oscillator

Table 6. Design Parameters

DESIGN PARAMETEREXAMPLE VALUE
Load Impedance4 Ω to 32 Ω
Supply Voltage5 V to 12 V

Detailed Design Procedure

The Detailed Design Procedure can be found in the Detailed Design Procedure section.

Application Curve

LM386 lm386_d001.gif
Figure 21. Supply Current vs Supply Voltage

AM Radio Power Amplifier

LM386 lm386_am_radio_power_amplifier.gif Figure 22. AM Radio Power Amplifier

Design Requirements

Table 7. Design Parameters

DESIGN PARAMETEREXAMPLE VALUE
Load Impedance4 Ω to 32 Ω
Supply Voltage5 V to 12 V

Detailed Design Procedure

The Detailed Design Procedure can be found in the Detailed Design Procedure section.

Application Curve

LM386 lm386_d001.gif
Figure 23. Supply Current vs Supply Voltage