CHAPTER 10 : SINGLE STAGE TRANSISTOR AMPLIFIERS¶
Example 10.2 : page number 243-244¶
In [1]:
from math import pi
#Variable declaration
f_min=2.0; #Minimum frequency of operation of amplifier, kHz
f_max=10.0; #Maximum frequency of operation of amplifier, kHz
RE=560.0; #Emitter resistor, тДж
#Calculations
#X_CE(Emitter capacitor's capacitive reactance)
#X_CE=1/(2*pi*f_min*CE)=RE/10
#From the above equation.
CE=1/(2*pi*f_min*1000*(RE/10)); #Emitter capacitor, F,
CE=CE*10**6; #Emitter capacitor, ЁЭЬЗF
#Results
print('The value of the emitter capacitor = %.2f ЁЭЬЗF'%(CE));
Example 10.5: Page number 252-253¶
In [3]:
%matplotlib inline
import matplotlib.pyplot as plt
#Variable declaration
VCC=15.0; #Collector supply voltage in V
VBE=0.7; #Base-emitter voltage, V
R1=10.0; #Resistor R1, kтДж
R2=5.0; #Resistor R2, kтДж
RC=1.0; #Collector resistor, kтДж
RE=2.0; #Emitter resistor, kтДж
RL=1.0; #Load resistor, kтДж
#Calculation
#(i)
#For d.c load line, from the equation: VCE=VCC-IC*(RC+RE),
#VCE is maximum when IC=0 and IC is maximum when VCE=0.
VCE_max=VCC; #Maximum collector-emitter voltage, V
IC_max=VCC/(RC+RE); #Maximum collector current, mA
#plot
VCE_plot=[i for i in range(0,(int)(VCC+1))]; #Plot variable for V_CE
IC_plot=[((VCC-i)/(RC+RE)) for i in (VCE_plot[:])]; #Plot variable for I_C
plt.subplot(211)
plt.xlim(0,20)
plt.ylim(0,6)
plt.plot(VCE_plot,IC_plot);
plt.xlabel("VCE(V)");
plt.ylabel("IC(mA)");
plt.title("d.c load line");
#(ii)
#For operating point:
#Assuming VCC drops almost completely across R1 and R2,
V2=VCC*R2/(R1+R2); #Voltage across resistor R2, V
IE=(V2-VBE)/RE; #Emitter current, mA
IC=IE; #Collector current, mA
VCE=VCC-IC*(RC+RE); #Collector-emitter voltage , V
print("The operating point: VCE=%.2fV and IC=%.2fmA."%(VCE,IC));
#(iii)
#For a.c load line
RAC=(RC*RL)/(RC+RL); #a.c load, kтДж
VCE_ac_max=VCE+IC*RAC; #Maximum collector-emitter voltage, V
IC_ac_max=IC+VCE/RAC; #Maximum collector current, mA
print("Maximum v_CE=%.2fV and maximum i_C=%.2fmA"%(VCE_ac_max,IC_ac_max));
#plot
vCE_plot=[0,VCE_ac_max]; #Plot variable for V_CE
iC_plot=[IC_ac_max,0]; #Plot variable for I_C
plt.subplot(212)
plt.xlim(0,10)
plt.ylim(0,20)
plt.plot(vCE_plot,iC_plot);
plt.xlabel("vCE(V)");
plt.ylabel("iC(mA)");
plt.title("a.c load line");
Example 10.6: Page number 253-254¶
In [5]:
%matplotlib inline
import matplotlib.pyplot as p
#Variable declaration
RC=10; #Collector resistor, kтДж
RL=30; #Load resistor, kтДж
VCC=20; #Collector supply voltage, V
IC=1; #Collector current, mA
VCE=10; #Collector-emitter voltage, V
#Calculations
#For d.c load line:
#From the equation: VCE=VCC-IC*(RC+RE),
#When VCE=0, IC is maximum.
#Emitter resistor is neglected, assuming it as negligible
IC_max=VCC/RC; #Maximum collector current, mA
#And, when IC=0, VCE is maximum
VCE_max=VCC; #Maximum collector-emitter voltage, V
#plot
p.subplot(211)
p.xlim(0,20)
p.ylim(0,5)
VCE_plot=[0,VCE_max]; #Plot variable for V_CE
IC_plot=[IC_max,0]; #Plot variable for I_C
p.plot(VCE_plot,IC_plot);
p.xlabel("VCE(V)");
p.ylabel("IC(mA)");
p.title("d.c load line");
#For a.c load line:
RAC=(RC*RL)/(RC+RL); #a.c Load resistor, kтДж
VCE_ac_max=VCE+IC*RAC; #Maximum collector-emitter voltage, V
IC_ac_max=IC+ VCE/RAC; #Maximum collector current, mA
#plot
p.subplot(212)
p.xlim([0,25])
p.ylim([0,5])
vCE_plot=[0,VCE_ac_max]; #Plot variable for V_CE
iC_plot=[IC_ac_max,0]; #Plot variable for I_C
p.plot(vCE_plot,iC_plot);
p.xlabel("vCE(V)");
p.ylabel("iC(mA)");
p.title("a.c load line");
Example 10.7 : Page number 254-255¶
In [6]:
%matplotlib inline
import matplotlib.pyplot as p
#Variabe declaration
VCE_Q=8.0; #Q-point collector emitter voltage, V
IC_Q=1; #Q-point collector current, mA
ic_positive_peak=1.5; #Collector current at positive peak of signal, mA
ic_negative_peak=0.5; #Collector current at negative peak of signal, mA
vce_positive_peak=7; #Collector emitter voltage at positive peak of signal, V
vce_negative_peak=9; #Collector emitter voltage at negative peak of signal, V
#Plot
vce_plot=[vce_positive_peak,vce_negative_peak]; #Plot variable of vce
ic_plot=[ic_positive_peak,ic_negative_peak]; #Plot variable of ic
p.xlim(0,10)
p.ylim(0,2)
p.plot(vce_plot,ic_plot);
p.xlabel("vCE(V)");
p.ylabel("iC(mA)");
p.title("a.c load line");
p.grid();
Example 10.8 : Page number 256¶
In [7]:
#Variable declaration
VCC=10.0; #Collector supply voltage, V
RC=2.0; #Collector resistor, kтДж
Rin=1.0; #Input resistance, kтДж
beta=60.0; #Base current amplification factor
RL=0.5; #Load resistor, kтДж
#Calculation
RAC=(RC*RL)/(RC+RL); #a.c load resistor, kтДж
Av=beta*(RAC/Rin); #Voltage gain
#Results
print("Voltage gain= %d."%Av);
Example 10.9 : Page number 256¶
In [8]:
#Variable declaration
V_in=1.0; #Input voltage , mV
RC=10.0; #Collector resistor, kтДж
Rin=2.5; #Input resistance, kтДж
beta=100.0; #Base current amplification factor
RL=10.0; #Load resistor, kтДж
#Calculations
RAC=(RC*RL)/(RC+RL); #Effective load, kтДж
Av=beta*(RAC/Rin); #Voltage gain
V_out=V_in*Av; #Output voltage, V
#Results
print("Output voltage= %dmV."%V_out);
Example 10.10 : Page number 256-257¶
In [9]:
#Variable declaration
change_in_IB=10.0; #Change in base current, ЁЭЬЗA
change_in_IC=1.0; #Change in collector current, mA
change_in_VBE=0.02; #Change in Base-emitter voltage, V
RC=5.0; #Collector resistor, kтДж
RL=10.0; #Emitter resistor, kтДж
#Calculations
#(i)
beta=(change_in_IC*1000)/change_in_IB; #Base current amplification factor
#(ii)
Rin=(change_in_VBE/change_in_IB)*1000; #Input impedance, kтДж
#(iii)
RAC=round((RC*RL)/(RC+RL),1); #a.c load, kтДж
#(iv)
Av=beta*RAC/Rin; #Voltage gain
#(v)
Ap=beta*Av; #Power gain
#Results
print("Beta= %d."%beta);
print("Input impedance=%d kтДж."%Rin);
print("a.c load=%.1f kтДж."%RAC);
print("Voltage gain= %d."%Av);
print("Power gain=%d."%Ap);
Example 10.11 : Page number 257¶
In [10]:
#Variable declaration
beta=50.0; #Base current amplification factor
RC=3.0; #Collector resistor,kтДж
RL=6.0; #Load resistor, kтДж
Rin=0.5; #Input impedance, kтДж
Vin=1; #Input voltage, mV
#Calculation
RAC=(RC*RL)/(RC+RL); #a.c load, kтДж
Av=beta*RAC/Rin; #Voltage gain
Vout=Vin*Av; #Output voltage, V
#Results
print("Output voltage=%dmV"%Vout);
Example 10.12 : Page number 257-258¶
In [11]:
#Variable declaration
VT=6.0; #Collector potential, V
R1=1.0; #Resistor R1, kтДж
R2=2.0; #Resistor R2, kтДж
VB_found=4.0; #Measured base voltage, V
#Calculations
VB=(VT*R1)/(R1+R2); #Theoretical base voltage, V
if(VB_found==VB):
print("The circuit is operating properly.");
else:
print("The circuit is not operating properly.");
Example 10.13 : Page number 258-259¶
In [12]:
#Variable declaration
VCC=10.0; #Collector supply voltage, V
R1=40.0; #Resistor R1, kтДж
R2=10.0; #Resistor R2, kтДж
RC=6.0; #Collector resistor, kтДж
RE=2.0; #Emitter resistor, kтДж
beta=80; #Base current amplification factor
VBE=0.7; #Base emitter voltage, V
#Calculations
V2=(VCC*R2)/(R1+R2); #Voltage across resistor R2, V
VE=V2-VBE; #Emitter voltage, V
IE=VE/RE; #Emitter current, mA
re=25/IE; #a.c emitter resistance, тДж
#Results
print("a.c emitter resistance= %.2f тДж."%re);
Example 10.14 : Page number 262-263¶
In [13]:
#Variable declaration
VCC=20.0; #Collector supply voltage, V
VBE=0.7; #Base-emitter voltage, V
R1=150.0; #Resistor R1, kтДж
R2=20.0 #Resistor R2, kтДж
RC=12.0; #Collector resistor, kтДж
RE=2.2; #Emitter resistor, kтДж
#Calculations
V2=round(VCC*R2/(R1+R2),2); #Voltage across R2, V
VE=round(V2-VBE,2); #Voltage across emitter resistor, V
IE=round(VE/RE,2); #Emitter current, mA
re=round(25/IE,1); #a.c emitter resistance, тДж
#(i)
#CE(emitter capacitor) connected in the circuit:
Av=(RC*1000)/re; #Voltage gain for emitter capacitor connected.
print("(i)Voltage gain= %d."%Av);
#(ii)
#CE(emitter capacitor) removed from the circuit:
Av=(RC*1000)/(re+RE*1000); #Voltage gain for emitter capacitor removed.
print("(ii)Voltage gain= %.2f."%Av);
#Note: The answer in the text book has been approximated to 5.38 but it's actually coming 5.37.
Example 10.15 : Page number 263¶
In [14]:
#Variable declaration
RC=6.0; #Collector resistor, kтДж
RL=12.0; #Load resistor, kтДж
re=33.3; #a.c emitter resistance, тДж
#Calculations
RAC=RC*RL/(RC+RL); #a.c effective load, kтДж
Av=RAC*1000/re; #Voltage gain
#Result
print("Voltage gain= %d."%Av);
Example 10.16 : Page number 263-264¶
In [15]:
#Variable declaration
VCC=9.0; #Collector supply voltage, V
VBE=0.7; #Base-emitter voltage, V
R1=240.0; #Resistor R1, kтДж
R2=30.0 #Resistor R2, kтДж
RC=20.0; #Collector resistor, kтДж
RE=3.0; #Emitter resistor, kтДж
#Calculations
#(i)
V2=round(VCC*R2/(R1+R2),1); #Voltage across R2, V
VE=round(V2-VBE,1); #Voltage across emitter resistor, V
IE=round(VE/RE,1); #Emitter current, mA
re=25/IE; #a.c emitter resistance, тДж
#(ii)
Av=RC*1000/re; #Voltage gain
#(iii)
V_C_in=V2; #d.c voltage across input capacitor, V
V_C_E=VE; #d.c vooltage across emitter capacitor, V
#Results
print("(i) a.c emitter resistance=%d тДж."%re);
print("(ii) Voltage gain =%d."%Av);
print("(iii) d.c voltage across input capacitor= %dV and emitter capacitor=%.1fV."%(V_C_in,V_C_E));
Example 10.17 : Page number 264-265¶
In [16]:
#Variable declaration
VCC=15.0; #Collector supply voltage, V
VBE=0.7; #Base-emitter voltage, V
R1=40.0; #Resistor R1, kтДж
R2=10.0 #Resistor R2, kтДж
RC=2.0; #Collector resistor, kтДж
RE=1.0; #Emitter resistor, kтДж
RL=1.0; #Load resistor, kтДж
beta=100; #Base current amplification factor
#Calculation
#(i) D.C bias levels
V2=VCC*R2/(R1+R2); #Voltage across R2, V
VE=round(V2-VBE,1); #Voltage across emitter resistor, V
IE=round(VE/RE,1); #Emitter current, mA
IC=IE; #Collector current, mA
IB=IC/beta; #Base current, mA
VC=VCC-IC*RC; #Collector voltage, V
print("(i) D.C bias levels: V2=%dV, VE=%.1fV, IE=%.1fmA, IC=%.1fmA, IB=%.3fmA and VC=%.1fV."%(V2,VE,IE,IC,IB,VC));
#(ii)
Cin_V=V2; #Voltage across Cin capacitor, V
CE_V=VE; #Voltage across CE capacitor, V
CC_V=VC; #Voltage across CC capacitor, V
print("(ii) D.c voltage across: Cin=%dV and CE=%.1fV and CC=%.1fV."%(Cin_V,CE_V,CC_V));
#(iii)
re=round(25/IE,1); #a.c emitter resistance, тДж
print("(iii) a.c emitter resistance=%.1fтДж."%re);
#(iv)
RAC=round(RC*RL/(RC+RL),3); #Total a.c collector resistance, kтДж
Av=RAC/(re/1000); #Voltage gain
print("(iv) Voltage gain=%.1f."%Av);
#(v)
print("(v) VC>VE. Therefore, the transistor is in active state." );
Example 10.18 : page number 265¶
In [17]:
#Variable declaration
Av=132.0; #Voltage gain
beta=200.0; #Base current amplification factor
P_in=60.0; #Input power, ЁЭЬЗW
#Calculations
Ap=beta*Av; #Power gain
P_out=Ap*(P_in/10**6); #Output power, W
#Results
print("The power gain = %d and output power = %.3fW."%(Ap,P_out));
Example 10.19 : page number 265-266¶
In [18]:
#Variable declaration
IB=200.0; #Base current, microampere
IE=10.0; #Emitter current, mA
R1=27.0; #Resistor R1, kilo ohm
R2=13.0 #Resistor R2, kilo ohm
RC=4.7; #Collector resistor, kilo ohm
RE=2.2; #Emitter resistor, kilo ohm
#Calculations
#(i)
IC=IE-(IB/1000); #Collector current, mA
beta=IC/(IB/1000); #Current gain
print("(i) Current gain=%d"%beta);
#(ii)
#a.c emitter resistance is neglected, voltage gain=(collector resistor)/(emitter resistor)
Av=RC/RE; #Voltage gain
print("(ii) Voltage gain=%.2f"%Av);
#(iii)
Ap=round(beta*Av,0); #Power gain
#Results
print("(iii) Power gain=%d."%Ap);
Example 10.20 : Page number 266-267¶
In [19]:
#Variable declaration
VCC=30.0; #Collector supply voltage, V
VBE=0.7; #Base emitter voltage, V
R1=45.0; #Resistor R1, kтДж
R2=15.0 #Resistor R2, kтДж
RC=10.0; #Collector resistor,kтДж
RE=7.5; #Emitter resistor, kтДж
beta=200.0; #Base current amplification factor
#Calculations
V2=round(VCC*R2/(R1+R2),1); #Voltage across R2, V (Voltage divider rule)
VE=V2; #Voltage across emitter resistor(base-emitter voltage is neglected), V
IE=VE/RE; #Emitter current, mA (OHM's LAW)
re=25/IE; #a.c emitter resistance, ohm
Zin_base=(beta*re)/1000; #input impedance of transistor base,kтДж
R1_R2=(R1*R2)/(R1+R2); #Parallel resistance between R1 and R2, kтДж
Zin=((R1_R2)*Zin_base)/(R1_R2+Zin_base); #Input impedance of the amplifier circuit, kтДж
#Result
print("The input impedance of the amplifier circuit= %.2f kтДж."%Zin);
#Note: The input impedance of the amplifier circuit is approximated as 3.45 kтДж in the text book, but actually it's 3.46 kтДж.
Example 10.21 : Page Number 268-269¶
In [20]:
#Variable declaration
VCC=10.0; #Collector supply voltage, V.
RC=1.5; #Collector resistor, kтДж.
R1=18.0; #Resistor R1, kтДж.
R2=4.7; #Resistor R2, kтДж.
RE1=300.0; #Emitter resistor 1, тДж.
RE2=900.0; #Emitter resistor 2, тДж.
VBE=0.7; #Base-emitter voltage, V.
beta=150.0; #Base current amplification factor.
#Calculations
V2=round(VCC*R2/(R1+R2),1); #d.c voltage across R2, V. (Voltage divider rule)
VE=round(V2-VBE,1); #d.c voltage across RE, V.
IE=round((VE/(RE1+RE2))*1000,2); #d.c emitter current, mA.(OHM'S LAW)
re=round(25/IE,1); #a.c emitter resistance, тДж.
Av=RC*1000/(re+RE1); #Voltage gain
Zin_base=(beta*(re+RE1))/1000; #Input impedance of transistor base, kтДж.
#Results
print("The voltage gain of the swamped amplifier= %.2f."%Av);
print("Input impedance of transistor base of the swamped amplifier= %.2f kтДж."%Zin_base);
#Note:In the textbook Av is approximated to 4.66and Zin_base to 48.22 kilo ohm, but the actual answers come as 4.67 and 48.21 kilo ohm.
Example 10.22 : Page number 269¶
In [21]:
#Variable declaration
RC=1.5; #Collector resistor, kтДж.
RE1=300.0; #Emitter resistor 1, тДж.
re=21.5; #a.c emitter resistance, тДж.
#Calculations
Av=round(RC*1000/(re+RE1),2); #Voltage gain.
Av_1=round(RC*1000/(2*re+RE1),2); #Voltage gain when re doubles.
change_in_gain=round(Av-Av_1,2); #Change in voltage gain.
change_percentage=change_in_gain*100/Av; #Change percentage
#Results
if(change_in_gain>0):
print("The percentage change from the original value= %.2f%%(decrease)"%change_percentage);
else:
print("The percentage change from the original value= %.2f%%(increase)"%change_percentage);
#Note: The percentage has been approximated in the text book as 6.22%, but the answer comes as 6.42%.
Example 10.23 : Page number 269-270¶
In [22]:
#Variable declaration
VCC=10.0; #Collector supply voltage, V
VBE=0.7; #Base emitter voltage, V
R1=10.0; #Resistor R1, kilo ohm
R2=2.2; #Resistor R2, kilo ohm
RC=4.0; #Collector resistor, kilo ohm
RE=1.1; #Emitter resistor, kilo ohm
beta=200.0; #Base current amplification factor
RE1=210.0; #Emitter resistor 1 of swamped amplifier, ohm.
RE2=900.0; #Emitter resistor 2 of swamped amplifier, ohm.
#Calculations
V2=round(VCC*R2/(R1+R2),1); #d.c voltage across R2, V. (Voltage divider rule)
VE=round(V2-VBE,1); #d.c voltage across RE, V.
IE=(VE/RE); #d.c emitter current, mA.(OHM'S LAW)
re=25/IE; #a.c emitter resistance, ohm.
#(i) Zin_base:
Zin_base_standard=(beta*re)/1000; #input impedance of transistor base for standard amplifier , kilo ohm.
Zin_base_swamped=(beta*(re+RE1))/1000; #input impedance of transistor base for swamped amplifier, kilo ohm.
#(ii) Zin:
#input impedance for standard amplifier circuit
Zin_standard=(((R1*R2)/(R1+R2))*Zin_base_standard)/(Zin_base_standard +((R1*R2)/(R1+R2))); #kilo ohm
#input impedance for standard amplifier circuit
Zin_swamped=(((R1*R2)/(R1+R2))*Zin_base_swamped)/(Zin_base_swamped +((R1*R2)/(R1+R2))); #kilo ohm
#Results
print("(i) input impedance of transistor base for standard amplifier= %d kilo ohm"%Zin_base_standard);
print(" input impedance of transistor base for swamped amplifier= %d kilo ohm"%Zin_base_swamped);
print("(ii) input impedance for standard amplifier= %.2f kilo ohm"%Zin_standard);
print(" input impedance for swamped amplifier= %.2f kilo ohm"%Zin_swamped);
Example 10.24 : Page number 270-271¶
In [23]:
#Variable declaration
RC=4.0; #Collector resistor, kilo ohm
re=25.0; #a.c emitter resistance, ohm (calculated in example 10.23)
RE_1=210.0; #Emitter resistor 1 of swamped amplifier,ohm
#Calculation
Av_standard=(RC*1000)/re; #Voltage gain of standard common emitter amplifier
Av_swamped=(RC*1000)/(re+RE_1); #Voltage gain of swamped amplifier
#Results
print("The voltage gain of standard amplifier=%d."%Av_standard);
print("The voltage gain of swamped amplifier=%d."%Av_swamped);
Example 10.26 : Page number 273-274¶
In [24]:
#Variable declaration
A_0=1000.0; #Open circuit voltage gain
R_in=2.0; #Input resistance, kilo ohm
R_out=1.0; #Output resistance, ohm
RL=4; #Load resistor across the output, ohm
I_2=0.5; #Output signal current, A.
#Calculations
#Since A_0*(I_1*R_in) = I_2*(R_out+RL)
I_1=I_2*(R_out+RL)/(A_0*(R_in*1000)); #Input current, A
V_1=I_1*(R_in*1000); #Input signal voltage, V
V_1=V_1*1000; #Input signal voltage, mV
print("The required input signal voltage =%.1fmV"%V_1);
Example 10.27 : Page number 274¶
In [25]:
#Variable declaration
A_0=1000.0; #Open circuit voltage gain
R_in=7.0; #Input resistance, kilo ohm
R_out=15.0; #Output resistance, ohm
RL=35.0; #Load resistor across the output, ohm
R_s=3.0; #Internal resistance, kilo ohm
E_s=10.0; #Input signal voltage, mV.
#Calculations
#(i)
I_1=E_s*(10**-3)/(R_s*1000+R_in*1000); #Input current, A
V_1=I_1*(R_in*1000); #Voltage across input resistance, V
#Since, A_v=V_2/V_1 = A_0*RL/(R_out+RL)
A_v=A_0*RL/(R_out+RL); #Voltage gain
V_2=A_v*V_1; #Outout voltage, V
#(ii)
P_2=V_2**2/RL; #Output power, W
P_1=V_1**2/(R_in*1000); #Input power, W
A_p=round(P_2/P_1,-6); #Power gain
#Result
print("The magnitude of output voltage = %.1fV"%V_2);
print("The power gain =%de-06."%(A_p/10**6));
Example 10.28 : Page number 274-275¶
In [26]:
#Variable declaration
A_v=80.0; #Voltage gain
V_2=1.0; #Output voltage, V
A_i=120.0; #Current gain
RL=2; #Load resistor, kilo ohm
#Calculation
V_1=(V_2/A_v)*1000; #Input signal voltage, mV
#Since, A_i=A0*R_in/(R_out+RL) and A_v=A0*RL/(R_out+RL)
#So, A_v/A_i=RL/R_in
R_in=RL*A_i/A_v; #Input resistance, kilo ohm
I_1=V_1/R_in; #Input current, ╬╝A
A_p=A_i*A_v; #Power gain
#Results
print("Necessary input signal voltage= %.1fmV"%V_1);
print("Input signal current =%.2f ╬╝A"%I_1);
print("Power gain = %d."%A_p);
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