Chapter11-Power Amplifiers

Ex1-pg371

In [2]:
##Ex11_1
import math
VCC = 20.##collector voltage
RL = 12.##load resistance
print'%s %.2f %s'%("VCC = ",(VCC),"V")
print'%s %.2f %s'%("RL = ",(RL),"ohm")
Pi_dc = (VCC**2)/(2.*RL)##input power
print'%s %.2f %s'%("Pi(dc) = (VCC^2)/(2*RL) = ",(Pi_dc),"W")
Po_ac = (VCC**2)/(8.*RL)##output power
print'%s %.2f %s'%("Po_ac = (VCC^2)/(8*RL) = ",(Po_ac),"W")
eta = Po_ac/Pi_dc##efficiency
print'%s %.2f %s'%("eta = Po_ac/Pi_dc = ",(eta*100.),"%")


## note : has modifed variables:
##        using Po_ac instead of Po(ac)
##        and   Pi_dc instead of Pi(dc).

## note: there is a misprinting in the above problem given in the textbook 
##       author want to ask for efficiency instead of frequency.

VCC =  20.00 V
RL =  12.00 ohm
Pi(dc) = (VCC^2)/(2*RL) =  16.67 W
Po_ac = (VCC^2)/(8*RL) =  4.17 W
eta = Po_ac/Pi_dc =  25.00 %

Ex2-pg371

In [3]:
##Ex11_2
import math
Po_ac = 64.##output power
eta = 0.3##efficiency
Pi_dc = Po_ac/eta##input power
print'%s %.2f %s'%("Po_ac = ",(Po_ac),"W")
print'%s %.2f %s'%("eta = ",(eta),"")
print'%s %.2f %s'%("Pi_dc = Po_ac/eta = ",(Pi_dc),"W")
power_losses = Pi_dc - Po_ac##power losses
print'%s %.2f %s'%("Power losses = Pi_dc - Po_ac = ",(power_losses),"W")

## note : has modifed variables:
##        using Po_ac instead of Po(ac)
##        and   Pi_dc instead of Pi(dc).

Po_ac =  64.00 W
eta =  0.30 
Pi_dc = Po_ac/eta =  213.33 W
Power losses = Pi_dc - Po_ac =  149.33 W

Ex3-pg372

In [4]:
##Ex11_3
import math
VCEmax = 18.## highest value for collector emitter voltage
VCEmin = 2.## lowest value for collector emitter voltage
VQ = 9.##operating point voltage
print'%s %.2f %s'%("VCEmin = ",(VCEmin),"V")
print'%s %.2f %s'%("VCEmax = ",(VCEmax),"V")
print'%s %.2f %s'%("VQ = ",(VQ),"V")
D2 = ((1./2.)*(VCEmax + VCEmin) - VQ)/(VCEmax - VCEmin)*100.##second harmonic distortion
print("D2 = ((1/2)*(VCEmax + VCEmin) - VQ)/(VCEmax - VCEmin)*100")
print'%s %.2f %s'%("   =",(D2),"%")

## note : for above problem there is a misprint for the formula given in solution in the textbook

VCEmin =  2.00 V
VCEmax =  18.00 V
VQ =  9.00 V
D2 = ((1/2)*(VCEmax + VCEmin) - VQ)/(VCEmax - VCEmin)*100
   = 6.25 %

Ex4-pg372

In [5]:
##Ex11_4
import math
##according to the given eqution for output current, we have:
I1 = 5.0
I2 = 0.9
I3 = 0.6
I4 = 0.3
I5 = 0.01
D2 = I2/I1## second harmonic distortion
D3 = I3/I1##third harmonic distortion
D4 = I4/I1##fourth harmonic distortion
D5 = I5/I1##fifth harmonic distortion
print'%s %.2f %s'%("I1 = ",(I1),"A")
print'%s %.2f %s'%("I2 = ",(I2),"A")
print'%s %.2f %s'%("I3 = ",(I3),"A")
print'%s %.2f %s'%("I4 = ",(I4),"A")
print'%s %.2f %s'%("I5 = ",(I5),"A")
print'%s %.2f %s'%("D2 = I2/I1 = ",(D2),"")
print'%s %.2f %s'%("D3 = I3/I1 = ",(D3),"")
print'%s %.2f %s'%("D4 = I4/I1 = ",(D4),"")
print'%s %.2f %s'%("D5 = I5/I1 = ",(D5),"")
D = ((D2**2.)+(D3**2)+(D4**2.)+(D5**2))**(1/2.)##total harmonic distortion
print'%s %.2f %s'%("D = [(D2^2)+(D3^2)+(D4^2)+(D5^2)]^(1/2) = ",(D*100),"%")

I1 =  5.00 A
I2 =  0.90 A
I3 =  0.60 A
I4 =  0.30 A
I5 =  0.01 A
D2 = I2/I1 =  0.18 
D3 = I3/I1 =  0.12 
D4 = I4/I1 =  0.06 
D5 = I5/I1 =  0.00 
D = [(D2^2)+(D3^2)+(D4^2)+(D5^2)]^(1/2) =  22.45 %

Ex5-pg373

In [6]:
##Ex11_5
import math
VCC = 9.##collector voltage
Vp = 5.##output peak voltage
VQ = VCC##operating point
VCEmax = VQ + Vp## maximum value of collector emitter voltage
VCEmin = VQ - Vp## minimum value of collector emitter voltage
print'%s %.2f %s'%("VCC = ",(VCC),"V")
print'%s %.2f %s'%("Vp = ",(Vp),"V")
print'%s %.2f %s'%("VQ = VCC = ",(VQ),"V")
print'%s %.2f %s'%("VCEmax = VQ + Vp = ",(VCEmax),"V")
print'%s %.2f %s'%("VCEmin = VQ - Vp = ",(VCEmin),"V")
eta = 50.*((VCEmax - VCEmin)/(VCEmax + VCEmin))##amplifier efficiency
print'%s %.2f %s'%("eta = 50*[(VCEmax - VCEmin)/(VCEmax + VCEmin)] = ",(eta),"%")

VCC =  9.00 V
Vp =  5.00 V
VQ = VCC =  9.00 V
VCEmax = VQ + Vp =  14.00 V
VCEmin = VQ - Vp =  4.00 V
eta = 50*[(VCEmax - VCEmin)/(VCEmax + VCEmin)] =  27.78 %

Ex6-pg373

In [7]:
##Ex11_6
import math
VCC = 20.##collector voltage
RL = 10.##load resistance
print'%s %.2f %s'%("VCC = ",(VCC),"V")
print'%s %.2f %s'%("RL = ",(RL),"ohm")
Pi_dc = (VCC**2)/(RL)##input power
print'%s %.2f %s'%("Pi(dc) = (VCC^2)/(RL) = ",(Pi_dc),"W")
Po_ac = (VCC**2)/(2.*RL)##output power
print'%s %.2f %s'%("Po_ac = (VCC^2)/(2*RL) = ",(Po_ac),"W")
eta = Po_ac/Pi_dc##efficiency
print'%s %.2f %s'%("eta = Po_ac/Pi_dc = ",(eta*100.),"%")


## note : has modifed variables:
##        using Po_ac instead of Po(ac)
##        and   Pi_dc instead of Pi(dc).

VCC =  20.00 V
RL =  10.00 ohm
Pi(dc) = (VCC^2)/(RL) =  40.00 W
Po_ac = (VCC^2)/(2*RL) =  20.00 W
eta = Po_ac/Pi_dc =  50.00 %

Ex7-pg373

In [8]:
##Ex11_7
import math
RL = 3.6*10**3##output impedence of power amplifier
RL_dash = 4.##resistance of speaker
n = (RL/RL_dash)**.5##turns ratio
print'%s %.2f %s'%("RL = ",(RL),"ohm") 
print'%s %.2f %s'%("RL_dash = ",(RL_dash),"ohm") 
print'%s %.2f %s'%("n = RL/RL_dash = ",(n),"") 
print("trun of ratio")
print(  "30 :  1")

RL =  3600.00 ohm
RL_dash =  4.00 ohm
n = RL/RL_dash =  30.00 
trun of ratio
30 :  1

Ex8-pg373

In [9]:
##Ex11_8
import math
VCC = 15.##collector voltage
Vp = 12.##output peak voltage
print'%s %.2f %s'%("VCC = ",(VCC),"V")
print'%s %.2f %s'%("Vp = ",(Vp),"V")
eta = 78.5*(Vp/VCC)##amplifier efficiency
print'%s %.2f %s'%("eta = 78.5*(Vp/VCC) = ",(eta),"%")

VCC =  15.00 V
Vp =  12.00 V
eta = 78.5*(Vp/VCC) =  62.80 %

Ex9-pg374

In [10]:
##Ex11_9
import math
VCC = 25.##collector voltage
Vi = 9.##inout rms voltage
RL = 10.##load resistnce
Vi_peak = 1.414*Vi##input peak voltage
Vo = Vi_peak##output peak voltage
Po_ac = (Vo**2)/(2.*RL)##output power
Io = Vo/RL##output current
IC = (2./math.pi)*Io##collector current
Pi_dc = VCC*IC##input power
eta = Po_ac/Pi_dc##efficiency
print'%s %.2f %s'%("VCC = ",(VCC),"V")
print'%s %.2f %s'%("Vi = ",(Vi),"V")
print'%s %.2f %s'%("RL = ",(RL),"ohm")
print'%s %.2f %s'%("Vi_peak = (2^2)Vi = ",(Vi_peak),"V")
print'%s %.2f %s'%("Vo = Vi_peak = ",(Vo),"V")
print'%s %.2f %s'%("Po_ac = (Vo^2)/(2*RL) = ",(Po_ac),"W")
print'%s %.2f %s'%("Io = Vo/RL = ",(Io),"A")
print'%s %.2f %s'%("IC = (2/%pi)*Io = ",(IC),"A")
print'%s %.2f %s'%("Pi_dc = VCC*IC = ",(Pi_dc),"W")
print'%s %.2f %s'%("eta = Po_ac/Pi_dc = ",(eta*100.),"%")

VCC =  25.00 V
Vi =  9.00 V
RL =  10.00 ohm
Vi_peak = (2^2)Vi =  12.73 V
Vo = Vi_peak =  12.73 V
Po_ac = (Vo^2)/(2*RL) =  8.10 W
Io = Vo/RL =  1.27 A
IC = (2/%pi)*Io =  0.81 A
Pi_dc = VCC*IC =  20.25 W
eta = Po_ac/Pi_dc =  39.98 %

Ex10-pg375

In [11]:
##Ex11_10
import math
VCC = 18.##collector voltage
Vp = 15.##output peak voltage
RL = 12.##load resistnce
print'%s %.2f %s'%("VCC = ",(VCC),"V")
print'%s %.2f %s'%("Vp = ",(Vp),"V")
print'%s %.2f %s'%("RL = ",(RL),"ohm")
Ip = Vp/RL##output peak current
Idc = (2./math.pi)*Ip##input direct current
print'%s %.2f %s'%("Ip = Vp/RL = ",(Ip),"A")
print'%s %.2f %s'%("Idc = (2/%pi)*Ip = ",(Idc),"A")
Pi_dc = VCC*Idc##input power
print'%s %.2f %s'%("Pi_dc = VCC*Idc = ",(Pi_dc),"W")
Po_ac = (Vp**2.)/(2.*RL)##output power
print'%s %.2f %s'%("Po_ac = (Vp^2)/(2*RL) = ",(Po_ac),"W")
eta = Po_ac/Pi_dc##efficiency
print'%s %.2f %s'%("eta = Po_ac/Pi_dc = ",(eta*100.),"%")

VCC =  18.00 V
Vp =  15.00 V
RL =  12.00 ohm
Ip = Vp/RL =  1.25 A
Idc = (2/%pi)*Ip =  0.80 A
Pi_dc = VCC*Idc =  14.32 W
Po_ac = (Vp^2)/(2*RL) =  9.38 W
eta = Po_ac/Pi_dc =  65.45 %

Ex11-pg375

In [12]:
##Ex11_11
import math
Vop_p = 7.##peak to peap output voltage
Vip_p = 100.*10**-3##peak to peap input voltage
Av = Vop_p/Vip_p
print("Av = output voltage/input voltage")
print'%s %.2f %s'%("   = ",(Av),"")##voltage gain

Av = output voltage/input voltage
   =  70.00

Ex12-pg375

In [13]:
##Ex11_12
import math
Ai = 50.##current gain
Av = 70.##voltage gain
print'%s %.2f %s'%("Ai = ",(Ai),"")
print'%s %.2f %s'%("Av = ",(Av),"")
Ap = Ai*Av##power gain
print'%s %.2f %s'%("Ap = Ai*Av = ",(Ap),"")

Ai =  50.00 
Av =  70.00 
Ap = Ai*Av =  3500.00

Ex13-pg375

In [14]:
##Ex11_13
import math
vc = 9.##collector voltage
ic = 3.*10**-3##collector current
Pd = vc*ic##power dissipated at collector junction
print'%s %.2f %s'%("vc = ",(vc),"V")
print'%s %.4f %s'%("ic = ",(ic),"A")
print'%s %.2f %s'%("Pd = vc*ic = ",(Pd),"W")

vc =  9.00 V
ic =  0.0030 A
Pd = vc*ic =  0.03 W

Ex14-pg376

In [15]:
##Ex11_14
import math
Pac = 3.2*10**-3##output power
Pd = 27.*10**-3##power dissipated collector junction
P_eta = Pac/Pd##power efficiency
print'%s %.4f %s'%("Pac = ",(Pac),"W")
print'%s %.2f %s'%("Pd = ",(Pd),"W")
print'%s %.2f %s'%("P_eta = Pac/Pd = ",(P_eta*100),"%")

Pac =  0.0032 W
Pd =  0.03 W
P_eta = Pac/Pd =  11.85 %