Chapter 9:Multi stage Amplifiers¶
Example 9.1 Page no.305¶
In [1]:
#Given
A1=30 #voltage gain 1
A2=50 #voltage gain 2
A3=80 #voltage gain 3
#Calculation
import math
A=A1*A2*A3 #overall Voltage Gain
Adb=20*math.log10(A) #Voltage Gain in dB
# Result
print " The overall Voltage Gain of the Multistage Amplifier Adb = ",round(Adb,2),"dB"
Example 9.2 Page no.312¶
In [1]:
Vcc=30.0 #V, collector bias junction voltage
Vi=1.4 #V, input voltage
Vbe=0.7 #V. base emitter voltage
B=300 #Beeta, gain factor
R1=27000.0 #Ohms, given resistance
R2=680.0 #Ohms given resistance
R3=24000.0 #Ohms
R4=2400.0 #Ohms
#Calculation
Ve=Vi-Vbe #V, voltage at emitter terminal
Ie1=Vbe/R2 #A, emitter current at 1st stage
Ic1=Ie1 #A, collector current
Vc1=Vcc-round(Ie1,3)*R1 #collector voltage at 1st stage
Vb2=Vc1 #V, base voltage at 2nd stage
Ve2=Vb2-Vbe #V emitter voltage at 2nd stage
Ie2=Ve2/R4 #A, emitter current at 2nd stage
Ic2=round(Ie2,3) #A collector current at 2nd stage
Vc2=Vcc-Ic2*R3
Vo=Vc2
#Displaying The Results in Command Window
print " The Voltage at the Output Terminal of Two Stage Direct Coupled Amplifier, Vo = ",Vo,"V"
Example 9.3 Page no.319¶
In [8]:
A=100 #voltage gain
f1=400 #Hz, frequency 1
f2=25*10**3 #Hz, frequency 2
f3=80 #Hz, frequency 3
f4=40*10**3 # Hz, frequency 4
#Calculation
import math
Adb=20*math.log10(A)
Adbc=Adb-3 #Lower by 3dB
# Result
print " The Gain at Cutoff Frequencies is, Adb (at Cutoff Frequencies) = ",Adbc,"dB"
#plot
from pylab import *
f1=[80,400,25000,40000]
Adb1=[37,40,40,37]
a=plot(f1,Adb1)
xlim(0,40000)
xlabel("$f(Hz)$")
ylabel("$AdB$")
ylim(0,50)
show(a1)
Example 9.4 Page no 325.¶
In [2]:
#all the quantities of R are resistances
R1=5600.0 #Ohms
R2=56000.0 #Ohms
R3=1100.0 #Ohms
#Calculation
Zi=R1*R2*R3/(R1*R2+R2*R3+R3*R1)
#Result
print " The Input Impedance, Zi = ",round(Zi/10**3,3),"kohm"
#(b) Calculate output Impedance
Ro1=3300.0 #Ohms
Ro2=2200 #Ohms
#Calculation
Zo=Ro1*Ro2/(Ro1+Ro2)
#Result
print " The Output Impedance, Zo = ",Zo/10**3,"kohm"
#(c) voltage gain
hfe=120 #current amplification factor
hie=1100.0 #Ohms, dynamic input resistance
R1=6800.0 #Ohms
R2=56000.0 #Ohms
R3=5600.0 #Ohms
R4=1100.0 #Ohms
#Calculation
Rac2=Ro1*Ro2/(Ro1+Ro2)
A2=-hfe*Rac2/hie
Rac1=R1*R2*R3*R4/(R1*R2*R3+R2*R3*R4+R1*R3*R4+R1*R2*R4)
Rac1=round(Rac1,0)
A1=-hfe*Rac1/hie
A1=round(A1,2)
A=A1*A2 #Overall Gain
#Result
print " The Overall Gain, A = ",round(A,0)
Example 9.5 Page no. 326¶
In [3]:
Rl=10000.0 #Ohms, resistance
Rg=470000.0 #Ohms dynamic input resistance
Cs=100*10**(-12) #F Capacitance
u=25 #amplification factor
rp=8000.0 #Ohms
Cc=0.01*10**(-6) #F, capacitance
#Calculation
import math
gm=u/rp #transconductance
Req=rp*Rl*Rg/(rp*Rl+Rl*Rg+Rg*rp) #equivalent resistance
Avm=(u/rp)*Req #voltage gain
Avmd=Avm**2 # Voltage Gain of Two Stages
Rd=(rp*Rl/(rp+Rl))+Rg
f1=1/(2*math.pi*Cc*Rd) #Lower Cutoff Frequency
f1d=f1/math.sqrt(math.sqrt(2)-1) #Lower Cutoff Frequency of Two Stages
Req =(rp*Rl)/(rp+Rl) #approximately
f2=1/(2*math.pi*Cs*Req) #Upper Cutoff Frequency
f2d=f2*math.sqrt(math.sqrt(2)-1) #Upper Cutoff Frequency of Two Stages
BW=f2d-f1d
#Bandwidth
# Result
print " The Voltage Gain of Two Stages, Avmd = ",round(Avmd,2)
print " The Bandwidth, BW = ",round(BW/10**3,0),"KHz"