# Chapter 3: Negative Feedback¶

## Example 3.1, Page 75¶

In [1]:
#Variable declaration
Aol=200;
f2_ol=10000;     # in Hz
B=0.04;

#Calculations&Results
Asp=Aol/(1+B*Aol);
print "Asp %.2f \n "%Asp;            #Result
print "Approximately Asp =1/B equal to %.0f \n"%(1/B);#result
S=Aol/Asp;
print "S =%.0f \n"%S;
f2_sp=f2_ol*S;
print "f2_sp %.0f Hz"%f2_sp;       #Result

Asp 22.22

Approximately Asp =1/B equal to 25

S =9

f2_sp 90000 Hz


## Example 3.2, Page 76¶

In [2]:
#Variable declaration
Asp1=20.
Asp=10**(Asp1/20);

#Calculations&Results
print "Asp =%.0f\n"%Asp;#Result
#Rf/Ri=Asp-1;
print "Rf/Ri=%.0f \n"%(Asp-1);#Result
print "Rf must be 9 times larger than Ri. \n There are many possibilities  ";#Result

Asp =10

Rf/Ri=9

Rf must be 9 times larger than Ri.
There are many possibilities


## Example 3.3, Page 82¶

In [3]:
#Variable declaration
Zin_ol=300*10**3;       #in Ohms
Zout=100;       #in Ohms
Aol=50000.;
Zout_ol=100.;
Asp=100;

#Calculations&Results
S=Aol/Asp;
print "S = %.0f"%S;#Result
Zin_sp=S*Zin_ol;
print "Zin_sp = %.0f Ohm"%Zin_sp;#Result
Zout_sp=Zout_ol/S;
print "Zout_sp = %.1f Ohm"%Zout_sp;#Result

S = 500
Zin_sp = 150000000 Ohm
Zout_sp = 0.2 Ohm


## Example 3.4, Page 88¶

In [4]:
#Variable declaration
R1=9000;        # in Ohm
R2=1000.;        #in Ohm

#Calculations&Results
B=R2/(R1+R2);
print "B is %.2f\n"%B;#Result
#Aps=1/B;
Aps=(R1+R2)/R2;
print "Aps = %.0f \n "%Aps;#Result

B is 0.10

Aps = 10