Audio Amplifier with wit h Volume Volume Control and Gain Switch Sonali Mishra Vellore Vellore Institute of Technology,Vellore Technology,Vellore
[email protected] Abstract —The Aim of t his Project is to implement a low voltage audio amplifier with volume control knob and gain toggle switch using an !"#$ Audio %p& 'C b( Te)as 'nstruments* Keywords-component; Keywords-component; formatting; style; styling; insert (key words)
I.
I NTR!"#TIN
The $u%io am&lifier is %esigne% using an 'M()* au%io am&lifier I# manufacture% +y teas instruments an% test the out&ut on an )ohm S&ea-er ta-ing in&ut from an au%io source reuiring a (./mm ac- generic m&( &layer , mo+ile &hone etc.. The 'M()* 'M()* is a &o3er am&lifier %esigne% for use in lo3 voltage consumer a&&lications. The gain is internally set to 20 to -ee& eternal &art count lo3, lo3, +ut the a%%ition of an eternal resistor an% ca&acitor +et3een &ins 1 an% ) 3ill increase the gain to any value from 20 to 200. The I# is suita+le for +attery o&eration *4 12 Volts , has a lo3 uiescent current %rain of 5m$ , features lo3 %istortion of a+out 0.26 for an )ohm loa% an% gain of 20. The in&uts are groun% reference% an% the heat %issi&ate% %uring o&eration at *V is 0.2 7atts. II.
#IR# #IR#" "IT !I$8 !I$8R R$M
The circuit %iagram of the am&lifier is sho3n +elo3. The connections connections to &ins 1 an% ) are left o&en as they are sho3n in a se&arate image. These &ins %etermine the gain of the am&lifier. The The #irc #ircuit uit can +e easil easily y im&l im&leme emente nte% % on a sol%er sol%er4l 4les esss +rea%+oar% +rea%+oar% using connecting connecting 3ires. 3ires.
9igure 2: #ircuit !iagram
The %iagram a+ove sho3s the eternal &arts reuire% for gain togg toggle le.. In conf config igur urat atio ion n $ the the gain gain is set set 200 200 3hil 3hilee in configuration ; the gain is set to /0. $ toggle s3itch is use% for s3itching +et3een the 2 values. III.
=>"IR=! #M<N=NTS R =>"IR=!
A. LM 386 Audio Audio Amplifier Amplifier IC $ +rief intro%uction of the I# has alrea%y +een given. This sectio section n a%%res a%%resses ses the ty&ic ty&ical al electr electrica icall an%
•
&erating su&&ly Voltage : 5412 Volts
•
>uiescent #urrent at VS?*V , VIN ?0 : 54) m$
•
ut&ut
•
Voltage gain : 2* B 5* %;
•
Total Carmonic !istortion at V S?*V, R '?)Ω an% <"T ?125m7 : 0.26
9igure 1: #ircuit %iagram
•
•
In&ut Resistance R IN Ω IN : /0- Ω
The 8ra&h sho3s the variation of the uiescent current 3ith res&ect to the change in Su&&ly Voltage. The Maimum uiescent current reuire% is 5.*m$ at 12 Volt 3hich is an i%eal value for +attery o&eration
The 8ra&h sho3s the variation of Voltage gain%; 3.r.t change in freuency CD. The +an%3i%th of the am&lifier is (00-CD 3hich covers the hearing freuency range 20CD4 20-CD
The &am& has T.C.! G16 for &o3er out&ut G1.27atts. $fter that it increases ra&i%ly an% reaches a very high value H106 at 0.( 7atts
9or R'? ) ,Vs? *V, the maimum out&ut voltage across the loa% resistance is 5 Volts
The &o3er Ceat %issi&ate% +y the %evice at Vs? *V is a&&roimately 0.2 3atts. The & am& has very lo3 Total harmonic %istortion0.240./6 in the lo3 an% mi% freuency +an%. The %istortion goes to E0.)6 at high freuencies E10FhD
B. Other Components •
#1 B ;y&ass #a&acitor B 10u9
•
#2 B 8ain #a&acitor B 10u9
•
#( B ut&ut %ecou&ling #a&acitor B 220u9
•
#/ B #a&acitor B 5Jn9
•
R1 B Resistance B 10Ω
•
R2 B 8ain Resistance B 1.2 F Ω
•
R( B '=! resistance B 1.2 F Ω
•
R5 B
•
R/ B S&ea-er 4 ) Ω
•
8reen colour '=!
•
S3itches B 2
•
!# voltage su&&ly +attery +an- B *V
has t3o com&onents: $n $# com&onent, 3hich is the am&lifie% in&ut signal, &lus a !# com&onent of 1K2 Vs ? (V. This +iase% voltage cannot +e fe% %irectly to a s&ea-er. The 2/0u9 electrolytic ca&acitor filters out the !# com&onent an% the remaining $# goes to the s&ea-er. •
The 0.0/u9 ca&acitor an% 10 ohm resistor &air from &in / to groun% are use% to &revent high freuency oscillations.
•
$ small electrolytic or tantalum ca& of a 10 u9 from &in J to groun% 3ill isolate the high gain in&ut stage of the 'M()* from &o3er su&&ly noise, hum, transients, etc.
•
$nother ca&acitor of 100 u9 is connecte% +et3een the &o3er su&&ly an% groun% to %eal &o3er su&&ly noise unsta+le &o3er su&&ly.This ca&acitor -ee&s the in&ut !# voltage sta+le for sta+le out&ut. V.
•
IV.
7RFIN8 9 TC= #IR#"IT •
This am&lifier circuit uses an 'M()*4N 'o3 voltage au%io &4am& I# 3hose &in out %iagram is given here:
•
!=$'IN8 7ITC <7=R S"<<'L NIS=
$nother common 3ay of %ealing 3ith &o3er su&&ly noise is a%%ing a small %ecou&ling ca&acitor 100u9 net to the I# &o3er &ins B #/ In my e&erience, the &resence of these ca&acitors turne% out to +e %ecisive, es&ecially 3hen 3or-ing on a +rea%+oar%. #ou&le of other a&&roaches may also +e use% to re%uce the noise li-e4 $ Fee& all com&onents as close to the I# as &ossi+le ; Fee& all signal lines as short as &ossi+le.
$#FN7'=!8M=NT •
•
•
•
•
Sonali Mishra eten%s her sincere gratitu%e to the VIT "niversity for the +rilliant infrastructural facilities offere% to the stu%ents, the #hancellor of VIT "niversity for &rovi%ing her the o&&ortunity to realiDe $nalogue #ircuit !esign &ractically, an% Mr $run M. for +eing a constant &illar of su&&ort an% gui%ance. R =9=R=N#=S 1A
htt&:KKlo3voltage.3or%&ress.comK2011K05K2(Klm()*4au%io4am&lifierK : $n ;log a+out electronics, &rogramming an% &hotogra&hy. $ com&rehensive analysis of the 'M4()* am&lifier has +een &rovi%e%.
2A
htt&:KK 333.ti.comKlitK%sKsymlin-Klm()*.&%f : The !atasheet of the 'M4 ()* as &rovi%e% +y Teas Instruments. The %ata sheet &rovi%es the ty&ical &erformance gra&hs an% electric characteristics of the I#.
(A
Table +, -lectrical Characteristics
