Chapter 6: Specialized Op Amps

Example 6.1, Page 176

In [7]:
#Variable declaration
R1=20000.;       #in Ohm
R2=400;         #in Ohm
Vinp=0.006;         #in V  (Vinp=Vin+)
Vinm=-0.006;         #in V   Vinp=Vin_)
Vh=0.010;         #in V

#Calculations&Results
Vad=Vinm*(1+R1/R2)-Vinp*R1/R2;          #------1 equation Va=0.606mV approx
print "Va = %f V"%Vad;
#for common mode
Vac=Vh*(1+R1/R2)-Vh*R1/R2
print "Va = %f V"%Vac;
Rf=50000;       #in Ohm
Ri=10000;         #in Ohm
Av=Rf/Ri;
print "Av = %.f"%Av;
Va=-0.606;       #V 
Vb=-Va;
Voutd=Av*(Vb-Va);
print "Desired differential input signal is Vb-Va= %.2f V"%Voutd;
Vout=(Vinp-Vinm)*(Rf/Ri)*(1+2*(R1/R2));
print "By using equation 6.1 given in book Vout =(Vinp-Vinm)*(Rf/Ri)*(1+2*(R1/R2))= %.2f V"%Vout;
CMRR=10**5;
Av=505;
Vincm=10*10**-3;
Voutcm=Vincm*Av/CMRR*10**6;
print "Vout(cm) = %.1f uV"%Voutcm
Va = -0.606000 V
Va = 0.010000 V
Av = 5
Desired differential input signal is Vb-Va= 6.06 V
By using equation 6.1 given in book Vout =(Vinp-Vinm)*(Rf/Ri)*(1+2*(R1/R2))= 6.06 V
Vout(cm) = 50.5 uV

Example 6.2, Page 180

In [11]:
#Variable declaration
Av=10;  #dB

#Calculations
Rg=(49.4*10**3)/(Av-1)*10**-3;

#Result
print "Rg = %.3f kohms"%Rg
Rg = 5.489 kohms

Example 6.3, Page 183

In [14]:
import math

#Variable declaration
Vp=10;      #in V
Vcc=15.;         #in V
Rf=50000.;       #in Ohm
Ri=2000;         #in Ohm
Rset=3*10**6;           #in Ohm

#Calculations&Results
Iset=(Vcc-0.5)/Rset;
print "Iset = %f A"%Iset
Anoise=1+Rf/Ri;
print "Anoise = %.f"%Anoise;
funity=200000.;      #in Hz
f2=funity/Anoise*10**-3;
print "f2 = %.2f kHz"%f2;
SR=0.11/10**-6;    #in V/S
fmax=SR/(2*math.pi*Vp)*10**-3;
print "fmax = %.2f kHz"%fmax
Iset = 0.000005 A
Anoise = 26
f2 = 7.69 kHz
fmax = 1.75 kHz

Example 6.4, Page 190

In [16]:
#Variable declaration
Refresh=60.;
Height=1024;
Width=1024;

#Calculations&Results
Pixelrate=Refresh*Height*Width;
print "pixels per second =%.f Pixelrate"%Pixelrate;
Tr=1/Pixelrate;
f2=0.35/(0.3*Tr)*10**-6;
print "f2 = %.1f MHz"%f2;
pixels per second =62914560 Pixelrate
f2 = 73.4 MHz

Example 6.5, Page 191

In [18]:
#Variable declaration
Vp=5.;           #in V
Vm=-Vp;
Rcontrol=22000.;     #In Ohm
Vd=0.7;         #in V

#Calculations&Results
Iabc=(Vp-Vm-Vd)/Rcontrol*10**3;
print "Iabc = %.3f mA"%Iabc;
#Using voltage divider
Loss=470./(33000+470);
print "Loss = %.3f"%Loss;
Vpp=0.050;          #in V
Vinmax=Vpp/Loss;
print "Vinmax = %.2f V"%Vinmax;
gm=0.010;           #in S
Iout=Vpp*gm*10**3;
print "Iout = %.1f mA"%Iout;
#maximum output
Rf=22000;           #in Ohm
Vout=Iout*Rf;
print "Vout = %.f V"%Vout;
Iabc = 0.423 mA
Loss = 0.014
Vinmax = 3.56 V
Iout = 0.5 mA
Vout = 11000 V

Example 6.6, Page 197

In [33]:
import math

#Variable declaration
Av=-20;
Ri=50000.;       #in Ohm
fc=100;     #in Hz

#Calculations&Results
#Av=-Rf/Ri
Rf=-Av*Ri*10**-6;
print "Value of Rf = %.f Mohms"%Rf;
Rb=2*Rf;
print "Value of Rb = %.f Mohms"%Rb;
C=1./(2*math.pi*Ri*fc)*10**9;
print "Value of C = %.1f nF"%C;
Value of Rf = 1 Mohms
Value of Rb = 2 Mohms
Value of C = 31.8 nF

Example 6.7, Page 205

In [34]:
#Variable declaration
Av=20.;          #in dB
Av1=10**(Av/20);            #ordinary gain
Rf=1500.;            #in Ohm (Assumption)

#Calculations
#Av=1+Rf/R  we know
R=Rf/(Av1-1);


print "R =%.f ohms"%R;
R =167 ohms