Design A Simple Low Voltage Audio

Amplifier

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O Lord!

Advance us in Pure Knowledge & Lead us to the Straight

Path.

(Ameen)

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Table of ContentsTable of Contents

SR.NO. CHAPTERS PAGE NO.

1. Abstract 04

2. Objectives 05

3. Introduction 06

4. Project description 07

4.1 Required components 07

4.2 IC LM386M-1 07

4.2(a) General description 07

4.2(b) Features 08

4.2(c) Applications 08

4.2(d) Equivalent schematic 09

4.3 Low voltage audio amplifier 09

4.3(a) circuit 09

4.3(b) PCB layout 10

4.3(c) Description 10

4.4 Pictures of project 11

5. References 12

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ABSTRACT

The main purpose of the present study is to design simple low cost

audio amplifier using IC LM386. There are different models of the

LM386 that have slightly different specifications such as LM 386N-1, LM

386N-3, LM 386N-4, LM 386M-1, LM 386MM-1. In this project we use

IC LM 386 M-1. This amplifier is suited for the low voltage amplification.

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OBJECTIVESTo be intuitative and innovative is the wit of soul and mind of human

being. This is what engineering demands from us that we must explore

new avenues and dimensions by tapping our in built capabilities. This

was the main motivating factor behind submitted project. The core

purpose behind this team work was to utilize the different brains in

order to create such a pragmatic innovation with the name of “LOW

VOLTAGE AUDIO POWER AMPLIFIER” using “IC LM 386 M-1”. We have

decided to go with the same spirit in the prospective times in order to

utilize our technical knowledge in the best possible manner. So that we

can prove ourselves to be the most utilitarian members of engineering

slot.

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INTRODUCTIONThis is a 0.125 milli watt mono amplifier module Kit using the LM386M-

1 IC. It will operate best from 4-18V DC and will work well from a

battery since the quiescent current drain is only 4 mA. It requires no

heat sink for normal use. The input and output are both ground

referenced. Maximum output will be obtained with a 18V power supply

and 8 ohm speaker. We also added LED parallel to the speaker, which

blinks with the bass of the music.

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PROJECT DESCRIPTIONRequired Components:

1μF non-electrolytic capacitor 1

1nF non-electrolytic capacitor 1

100μF electrolytic capacitor 1

10μF electrolytic capacitor 3

47nF non-electrolytic capacitor 1

10 ohm resistor (brown, black, black) 1

10k ohm potentiometer 1

IC: LM386M-1 Integrated Circuit 1

LED: Red LED 5

LED: Orange LED 5

9V dc-batteries 2

Printed Circuit Board 1

Mono audio pin 1

IC LM 386 M-1:

General Description:

The LM386 is a power 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 7

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 mill watts when operating from a 6 volt supply, making the

LM386 ideal for battery operation.

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

Applications:

AM-FM radio amplifiers

Portable tape player amplifiers

Intercoms

TV sound systems

Line drivers

Ultrasonic drivers

Small servo drivers

Power converters

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Equivalent Schematic and Connection Diagrams:

Fig 1 equivalent schematic and connection diagrams of LM 386M-1

LOW VOLTAGE AUDIO AMPLIFIER:

Circuit:

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Fig 2 Circuit of audio amplifier

PCB Layout:

Fig 3 PCB layout of audio amplifier circuit

Description:

There are only a few external components, the IC contains most of the

necessary circuitry.

1μF capacitor is the input coupling capacitor, which blocks any

DC that might be present on the input.

10μF capacitor between 1 and 8 pin of the IC, maintains DC bias

levels in the gain adjustment circuit (feed back bypass).

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10μF capacitor parallel to the battery, provides power supply

decoupling. A decoupling capacitor is a capacitor used

to decouple one part of an electrical network (circuit) from

another. Noise caused by other circuit elements is shunted

through the capacitor, reducing the effect they have on the rest

of the circuit.

100μF capacitor before the speaker is the output coupling

capacitor.

47nf capacitor 10Ω resistor act as a zobel network providing a

high frequency load to maintain stability where loud speaker

inductive reactance may become excessive.

10kΩ potentiometer provides adjustable input level attenuation.

Pictures of the project:

Following is the pictures of the project through different angles.

Fig 4 Implementation of PCB circuit on a PCB board

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Fig 5 components placed on a PCB board

Fig 6(a) finalizing of the project

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Fig 6(b) Final shape of the project

References

http://www.techlib.com/electronics/audioamps.html

http://www.biltek.tubitak.gov.tr/gelisim/elektronik/dosyalar/6/

LM386.pdf

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