Chapter 2: Noise

Example 2.1, page no. 18

In [1]:
# Variable Declaration
del_f = 2.00*pow(10,6)     # Bandwidth of interest (Hz)
T     = 300                # Operating Temperature (K)
k     = 1.38*pow(10,-23)   # Boltzmann's Constant (J/K)

# Calculation
import math                # Math Library
Pn    = k*T*del_f          # Power Output (W)

# Result
print "Maximum noise power output of the resistor, Pn =",round(Pn/pow(10,-13),4),"* 10^(-13) Watts"

Maximum noise power output of the resistor, Pn = 0.0828 * 10^(-13) Watts

Example 2.2, page no. 19

In [3]:
# Variable Declaration
del_f = 2.00*pow(10,6)          # Bandwidth of interest (Hz)
T     = 300                     # Operating Temperature (K)
k     = 1.38*pow(10,-23)        # Boltzmann's Constant (J/K)
R     = 10.00*pow(10,3)         # Input Resistance (Ohms)

# Calculation
import math                     # Math Library
Vn    = pow(4*k*T*del_f*R,0.5)  # RMS Noise Voltage (V)

# Result
print "The rms noise voltage at the input of the amplifier, Vn =",round(Vn/pow(10,-6),1),"microvolts"

The rms noise voltage at the input of the amplifier, Vn = 18.2 microvolts

Example 2.3, page no. 21

In [4]:
# Variable Declaration
del_f = 6.00*pow(10,6)               # Bandwidth of interest (Hz)
T     = 290                          # Operating Temperature (K)
k     = 1.38*pow(10,-23)             # Boltzmann's Constant (J/K)
R1    = 300                          # Input Resistance (Ohms)
R2    = 200                          # Device Resistance (Ohms)

# Calculation
import math                          # Math Library
Vn    = pow(4*k*T*del_f*(R1+R2),0.5) # Noise voltage (V)

# Result
print "The noise voltage at the input of the Television RF amplifier, Vn =",round(Vn/pow(10,-6),2),"uV"

The noise voltage at the input of the Television RF amplifier, Vn = 6.93 uV

Example 2.4, page no. 23

In [6]:
# Variable Declaration
A1  = 10                   # First Stage Voltage Gain
A2  = 25                   # Second Stage Voltage Gain
R11 = 600                  # First Stage Resistance (Ohms)
R12 = 1600                 # First Stage Resistance (Ohms)
R21 = 27000                # Second Stage Resistance (Ohms)
R22 = 81000                # Second Stage Resistance (Ohms)
R23 = 10000                 # Second Stage Resistance (Ohms)
R3  = 1.00*pow(10,6)        # Third Stage Resistance (Ohms)

# Calculation
import math                                  # Math Library
R1  = R11+R12                                # Resistance 1 (Ohms)
R2  = R21*R22/(R21+R22)+R23                  # Resistance 2 (Ohms)
Req = R1+(R2/pow(A1,2))+R3/((A1*A1)*(A2*A2)) # Input Noise Resistance (Ohms)

# Result
print "Input Noise Resistance, Req =",round(Req),"Ohms"

Input Noise Resistance, Req = 2518.0 Ohms

Example 2.5, page no. 28

In [7]:
# Variable Declaration
Req = 2518.00             # Resistance From Example 2.4 (Ohms)
Rt  = 600.00              # Resistance From Example 2.4 (Ohms)
Ra  = 50.00               # Output Impedance (Ohms)

# Calculation
import math               # Math Library
Req1 = Req-Rt             # Equivalent Resistance (Ohms)
NF   = 1+Req1/Ra          # Noise Figure

# Result
print "Noise Figure, F =",round(NF,1),"or",round(10*math.log10(NF),2),"dB"

Noise Figure, F = 39.4 or 15.95 dB

Example 2.6, page no. 29

In [8]:
# Variable Declaration
To  = 290                  # Operating Temperature (K)
Ra  = 50.00                # Antenna Resistance (Ohms)
Req = 30.00                # Equivalent Noise Resistance (Ohms)

# Calculation
import math                # Math Library
NF  = 1+Req/Ra             # Noise Figure
F   = 10*math.log10(NF)    # Noise Figure (dB)
Teq = To*(NF-1)            # Noise Temperature (K)
 
# Result
print "Noise Figure, F =",round(F,2),"dB"
print "Noise Temperature, Teq =",round(Teq),"K"

Noise Figure, F = 2.04 dB
Noise Temperature, Teq = 174.0 K