CHAPTER 20 LINEAR OP-AMP CIRCUITS

Example 20-1, Page 741

In [4]:
Rf=100.0                             #feedback path resistance Rf (KOhm)
R1=100.0                             #inverting input resistance R1(KOhm)
R2=1.0                               #inverting input  & drain resistance R2(KOhm)

Av1=(Rf/(R1**-1+R2**-1)**-1)+1          #maximum voltage gain
Av2=(Rf/R1)+1                           #minimum voltage gain

print 'maximum voltage gain = ',Av1
print 'minimum voltage gain = ',Av2

maximum voltage gain =  102.0
minimum voltage gain =  2.0

Example 20-2, Page 747

In [1]:
R1=1.2                                #inverting input resistance R1(KOhm)
R2=91.0                               #feedback resistance R2(KOhm)

Av1=-R2/R1                              #maximum voltage gain
Av2=0                                   #minimum voltage gain

print 'maximum voltage gain = ',round(Av1,2)
print 'minimum voltage gain = ',Av2

maximum voltage gain =  -75.83
minimum voltage gain =  0

Example 20-3, Page 747

In [6]:
R=1.5                                 #inverting input resistance R1(KOhm)
nR=7.5                                #feedback resistance(KOhm)

n=nR/R                                  #max. limit of voltage gain 
rf=nR/(n-1)                             #fixed resistor (KOhm)

print 'maximum positive voltage gain = ',n
print 'other fixed resistor = ',rf,'KOhm'

maximum positive voltage gain =  5.0
other fixed resistor =  1.875 KOhm

Example 20-4, Page 757

In [10]:
R1=1.0                                   #inverting input resistance R1(KOhm)
R2=100.0                                 #feedback resistance R2(KOhm)
R=10.0                                   #resistor of opamp in seconnd stage(KOhm)
Vin=10*10**-3                            #input voltage(V)
Vin_CM=10                                #common mode input voltage(V)
T=0.0001                                 #tolerance of resistor  

Av=(R2/R1)+1                             #preamp voltage gain
Av_CM=2*T                                #common mode voltage gain of 2nd stage
Vout=-Av*Vin                             #output siganl voltage(V)
Vout_CM=Av_CM*Vin_CM                    #output siganl voltage for common mode signal(V)

print 'output siganl voltage for common mode signal Vout(CM) = ',Vout_CM,'V'
print 'output siganl voltage Vout = ',Vout,'V'

output siganl voltage for common mode signal Vout(CM) =  0.002 V
output siganl voltage Vout =  -1.01 V

Example 20-5, Page 759

In [2]:
Rf=6.0                                   #feedback path resistance Rf (KOhm)
R1=1.0                                   #inverting input resistance R1(KOhm)
R2=2.0                                   #inverting input resistance R2(KOhm)
R3=3.0                                   #non-inverting input resistance R3(KOhm)
R4=4.0                                   #non-inverting input resistance R4(KOhm)
R5=5.0                                   #non-inverting input resistance R5(KOhm)

Av1=(-Rf/R1)                             #voltage gain1
Av2=(-Rf/R2)                             #voltage gain2
Av3=(1+(Rf/((R1**-1+R2**-1)**-1)))*(((R4**-1+R5**-1)**-1)/(R3+((R4**-1+R5**-1)**-1)))            #voltage gain3
Av4=(1+(Rf/((R1**-1+R2**-1)**-1)))*(((R3**-1+R5**-1)**-1)/(R4+((R3**-1+R5**-1)**-1)))            #voltage gain4

print 'Voltage gain channel-1 Av1 = ',Av1
print 'Voltage gain channel-2 Av2 = ',Av2
print 'Voltage gain channel-3 Av3 = ',round(Av3,2)
print 'Voltage gain channel-4 Av4 = ',round(Av4,2)

Voltage gain channel-1 Av1 =  -6.0
Voltage gain channel-2 Av2 =  -3.0
Voltage gain channel-3 Av3 =  4.26
Voltage gain channel-4 Av4 =  3.19

Example 20-6, Page 762

In [16]:
D0=1                           #digital input0 (binary)
D1=0                           #digital input1 (binary)
D2=0                           #digital input2 (binary)
D3=1                           #digital input3 (binary)
Vref=5                         #reference voltage(V)
N=4                            #no. of inputs

BIN=(D0*2**0)+(D1*2**1)+(D2*2**2)+(D3*2**3)   #decimal equivalent BIN
Vout=-((2*Vref*BIN)/2.0**N)                   #output voltage of converter(V)

print 'decimal equivalent BIN = ',BIN
print 'output voltage of converter Vout = ',Vout,'V'

decimal equivalent BIN =  9
output voltage of converter Vout =  -5.625 V

Example 20-7, Page 764

In [23]:
R2=51                               #feedback path resistance (KOhm)
R1=1                                #inverting input resistance R1(KOhm)
Bdc=125                             #current gain
Zout=75                             #open loop output impedance(Ohm)
AVOL=100000                         #741C voltage gain

Av=-R2/R1                          #closed loop voltage gain
B=R1/(R1+R2)                       #feedback fraction
Zout_CL=Zout/(1+(AVOL*B))          #closed loop output impedance(Ohm)
Isc=25.0/1000                      #shorted current for 741C op-amp(A)
Imax=Bdc*Isc                       #maximum load current(A)

print 'closed loop output impedance Zout(CL) = ',Zout_CL,'Ohm'
print 'maximum load current Imax = ',Imax,'A'

closed loop output impedance Zout(CL) =  75 Ohm
maximum load current Imax =  3.125 A

Example 20-8, Page 768

In [25]:
Vin=1.0                            #input voltage(V)
VCC=15                             #supply voltage(V)
R=10                               #inverting input resistance(KOhm)
Vin2=10.0                          #larger input(V)

iout=Vin/R                         #output current(mA)
RL_max=R*(VCC/Vin2-1)              #Maximum load resistance(KOhm) 

print 'Output current iout = ',iout,'mA'
print 'Maximum load resistance RL(max) = ',RL_max,'KOhm'

Output current iout =  0.1 mA
Maximum load resistance RL(max) =  5.0 KOhm

Example 20-9, Page 768

In [32]:
Vin=3.0                            #input voltage(V)
VCC=15                             #supply voltage(V)
R=15                               #inverting input resistance(KOhm)
Vin2=12.0                          #larger input(V)

iout=-Vin/R                         #output current(mA)
RL_max=(R/2.0)*(VCC/Vin2-1)         #Maximum load resistance(KOhm) 

print 'Output current iout = ',iout,'mA'
print 'Maximum load resistance RL(max) = ',RL_max,'KOhm'

Output current iout =  -0.2 mA
Maximum load resistance RL(max) =  1.875 KOhm

Example 20-10, Page 771

In [3]:
R2=47                                   #feedback path resistance (KOhm)
R1=1.0                                  #inverting input resistance R1(KOhm)
R3=100                                  #non-inverting input resistance R3(KOhm)
rds1=0.050                              #ohmic resistance of JFET (KOhm)
rds2=120.0                              #ohmic resistance of JFET (KOhm)

Av1=((R2/R1)+1)*(rds1/(rds1+R3))      #minimum voltage gain
Av2=((R2/R1)+1)*(rds2/(rds2+R3))      #maximum voltage gain

print 'Maximum voltage gain Av = ',round(Av2,2)
print 'Minimum voltage gain Av = ',round(Av1,3)

Maximum voltage gain Av =  26.18
Minimum voltage gain Av =  0.024
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