From Nu-FAST Karachi

1. 1
TABLE OF CONTENTS
Introduction 2
Objective 2
Block Diagram 2
Chemical Etching 2
Schematics 3
PCB Top Layout 4
PCB Back Layout 4
Components List 5
Components Working 6
Applications 9
Trouble Shooting 10

2. 2
Introduction:
The LM386 IC is a low voltage audio power amplifier with a default voltage gain of 20, which
can howeverbe increased to any value between 20 and 200 by simply placing an external series
RC circuit between pins 1 and 8.So pin 1 and 8 are gain controlling pins. In the amplifier circuit,
the output AC power is clearly larger than the input AC power reflecting the voltage, and thus
power, gain. The increase in AC power in going from the input terminals of the amplifier to the
output terminals are provided by the DC voltage source biasing the circuit. In the case of the
LM386 IC, the operating DC power source must have a voltage between 4V and 12V and supply
a current of 100 mA. So I provide it a power supply of 9 volt and 220 mA. These values of DC
voltage and current are readily provided by a battery so that an audio amplifier based on the
LM386 IC is very much amenable to battery operation.
Objective:
The purpose of the present experiment is to introduce the audio amplifiers using the popular
audio amplifier integrated circuit (IC) LM386 and then measuring the amplifier performance,
including its gain.How we control the gain and remove the noises by using LM386.
Block Diagram:
Chemical Etching:
There are two methods of making PCB
By CNC Machine
By Chemical Etching
The CNC Machine of NU_FAST University is out of order so I made PCB by Chemical Etching.

3. 3
The Method of Chemical Etching is given below.
Take a print of PCB layout and paste it on PCB board with Iron. After 5 minutes remove the
print of PCB layout then the traces will be combining on the Board. Put some quantity of Ferret
Chloride in a plastic box then mix it into water. Then put the board into the mixture of Ferret
Chloride. After 5 hours all the copper remove except traces because Ferret Chloride does not
react with Black carbon.
Now made holes in PCB board and put the components with the help of soldering wire and iron.
Schematic:

4. 4
PCB Top Layout:
PCB Bottom Layout:

5. 5
COMPONENTS LIST:
S.NO. COMPONENT VALUE/MODEL QTY. PRICE
1 Low Voltage Audio power IC LM386 1
2 Voltage regulator IC LM7809 1
3 Transformer 12-0-12 1 70
4 Speaker 8 ohm 1 70
5 Bridge rectifier IC KBL406G 1 15
6 Variable Resistor 10k , 5K 2 30
7 Capacitors 10uF/25V 4 5 x 4
8 Capacitor 100uF 1 2
9 Capacitor 2200uF/35V 1 10
10 Non-polar Capacitor 1uF 1 10
11 Non-polar Capacitor 100nF 1 2
12 Non-polar Capacitor 1nF 1 2
13 Non-polar Capacitor 47nF 1 2
14 Diode 1N4001 1 2
15 Resistor 1.2k 1 1
16 Resistor 10 ohm 1 1
17 Resistor 470 ohm 1 1
18 Wire --- 1 20
19 Switch --- 1 15
20 Audio Jack Male Connector Stereo 2 40
21 Audio Jack Female Connector Stereo 2 40
22 PCB Board --- 1 20
23 Heat sink --- 1 5
24 Jumper Wires --- --- 10
25 Soldering Wire --- 1 80
26 Soldering iron --- 1 150
27 Casing Material --- --- 100
28 Battery 9V 1 20

6. 6
Components Working:
LM386 IC:
The LM386 is a power amplifier IC 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.So pin 1
and 8 are gain controlling pins. I give input to pin no 3(positive) so out is non-inverting. If I give
input to pin no 2 the output will be out of phase.
LM7809 IC:
Voltage regulator gives constant voltage. In this project I used LM7809 IC which gives constant
9v. So I obtained 9V DC signal at output of Voltage Regulator IC.
Bridge Rectifier IC:
Bridge rectifier converts AC signal into DC signal. So this rectifier took 24v from transformer
and converted it into full wave pulsating DC signal.
Transformer:

7. 7
In this project center tapped transformer is used. I do not use the center ground wire I used
only (+12,-12). Step down transformer decreased the given voltage. It converts 220v into
24v. Remember that it does not convert AC signal to DC signal. It only gives 24v AC signal
to Bridge Rectifier.
Speaker:
It is used to hear the sound of audio signal. It is of 8 ohm and 3 watt.
Battery
It is used to give 9v DC voltage.
Variable Resistor:
It is used to give variable resistance to input signal. By increasing or decreasing the resistance by
variable resistor we can control the amount of input signal. In this circuit we control input signal
in such a way that output signal controlled automatically. I also used it as a gain controller
Capacitors:
It stores the charges. It also uses as a filter and reduces the ripple of DC. In Amplifier it is also
used to reduce the noises of sounds.

8. 8
Diode:
It is used in the circuit for safety purpose. It is reverse biased in circuit. If we even connected the
circuit in opposite direction it saves the others component from destroying.
Switch:
It is used to ON/OFF the amplifier. In this amplifier is used SPDT switch. SPDT stands for
single pole double through. In mid state the amplifier is OFF when I push the botton on left side
the amplifier beagan to work with DC battry and when I push the button on right side it will
began to work with DC power supply.
Audio Jack Male Connector:
Audio jack male connector is used to give or receive the input or output signal.
Audio Jack Female Connector:
Audio jack Female connector is used to give or receive the input or output signal.
PCB Board:
It is used to made traces for components. We connect the components with the help of traces on
this board. Its surface is made of copper. So by chemical etching only traces left on PCB.
Heat Sink:
It is used to cool down the IC. It takes heat from ICS and leave it in environment. In this way
ICS become safe from damaging due to heat.

9. 9
Jumper Wires:
Jumper wires are used to connect the PCB to those Components which are placed in casing such
as transformer,switch, speaker and LEDs.
Soldering Wire:
It is used to join the Pins of components on PCB with the help of soldering wire.
Soldering Iron:
It is used to join the pins of components on PCB with the help of soldering wire.
Casing:
To make a suitable casing for PCB of amplifier is much difficult. I worked very hard to make it.
It was much difficult to place the external components for example variable resistor and button
etc. in the casing. I made casing with wood material.
Applications:
The use of this amplifier is given below
 It is used as Computer speakers.
 It is used as Mobile speakers.
 It is used in radio.

10. 10
 Portable consumer products (toys, games, etc.
 Used as a AM/FM amplifiers
 Used as a Dc power supply of 9 v.
Trouble Shooting:
First of all I made Circut on Bread Board and check the working of amplifier. Some of noises
produced in the sound. I remove this noise by putting a capacitor and resistor between pin 1 and
8. When my circuit began to work completely then I put my circuit on PCB board after making
PCB layout and Chemical Etching. In the end I complete my project it was not working. I was so
worried and began to trouble shot the circuit. Finally I found the error of the circuit , the 1 uF
capacitor was short interlay because of giving lot of heat during soldering.
When I was checking my project I face a 220V shock from the input wires of transformer. One
of my cousins immediately switches off the AC voltage.