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//Example 3.4 //Determine the common mode rejection ratio(CMRR) of the difference amplifier
clc;
clear;
close;
Vcc = 10 ; // volt
Vee = -10 ; //volt
Iq = 0.8 ; //mA
Ie = 0.8 ; //mA
Rc = 12 ; //kilo-Ohm
Vt = 0.026 ; // volt
// Transistor parameter
beta = 100 ;
Rs = 0 ; //Ohm
Ro = 25 ; //kilo-Ohm
// The differential mode gain Ad
gm = (Ie/ 2*Vt) ;
// Ad = (gm*r*Rc/r+Rc) ; // where r is r-pi
// For Rb=0 , the differential mode gain is
Ad = (Ie/(2*Vt))*Rc;
//But
disp(' The differential mode gain Ad = ' +string(Ad)+ ' ' );
//The common mode gain Acm
// Acm = - (gm*Rc/1+2*gm*Re+2*Re/r)
Acm =-(Ad/(1+(((1+beta)*Ie*Ro)/(beta*Vt))));
disp(' The common mode gain Acm = ' +string(Acm)+ ' ' );
// The CMRR of difference amplifier is given as
Ad = Ad/2 ;
CMRR = abs(Ad/Acm);
disp(' The CMRR of difference amplifier is = ' +string(CMRR)+ ' ' );
// In decibel it can be expressed as
CMRRdb = 20*log10(CMRR);
disp(' In decibel CMRR is = ' +string(CMRRdb)+ ' ' );
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