1. Electronic Noise Time vs frequency domain noises
Noise present in devices
Noise propagation in filters

2. Noise in time domain

3. dBm is a unit used to measure physical power relative to 1 mW.
For example, if 2V is applied to 50, the physical power is:
P= 2^2/50 W = 4/50 W = 4*20 mW
P (dBm) = 10log(P/1mW) = 10log(80) = 10log(2^3*10) = 3* =19.03 dBm

4. Area For a given v(t), define: vf(t) v(t)
The power spectral density of v is:
Pv(f) = power of vf(t) = power of v(t) in a one Hertz bandwidth at f
The total power of v can be obtained by integrating Pv(f) over all f.
Pv(f)
Pv = 10*1M + 0.5*10*1M
= 15M (uV)2=15(mV)2
10(uV)2/Hz
Area
1MHz
2MHz

5. If the power spectral density of vn is flat (ind of f), vn is called white.
vn(t)
Pvn(f)

6. dBm or dBV2
Slope: 10dB/dec
log(f)

7. 1/f noise corner: the intersection of 1/f noise power spectral density and white noise power spectral density
dBm or dBV2
Slope: 10dB/dec
1/f noise corner
log(f)

8. Looks like signal + noise
Filtered noise:
Time domain:
Looks like signal + noise
Spectral domain:
Noisy filter shape

9. Example: white noise filtered by integrator
-20dB/dec

10. Filtered noise:
Chapter 9 Figure 06
Chapter 9 Figure 07

11. What’s the total power of white noise?
P = Pn(f)*BW = infinity P
White noise does not exist physically!
Physical “white” noise are filtered by LP/BP filters.

12. What’s the total power of 1/f noise?
goes to infinity if f2  inf or f1  0
Slope: -10dB/dec
k/f f2 f1
Hence need BP filtering

13. Equivalent noise bandwidth of a filter = the bandwidth of an ideal filter allowing the same amount of noise to pass through.
Chapter 9 Figure 09
-3dB BW
Noise in this band can still pass through
-3dB BW
noise BW

14. Device noise Capacitors do not generate noise
Inductors do not generator noise
Resistors generate white thermal noise
Active devices generate multiple kinds of noise

16. Chapter 9 Figure 12

17. Chapter 9 Figure 13
Regardless how complicated the network is, as long as all C’s can be reduced to Ceq, total voltage noise power on Ceq is
kT/Ceq

18. Rs L Rs L Vs
VRs iL
Regardless how complicated the network is, as long as all L’s can be reduced to Leq, total current noise power through Leq is kT/Leq

19. Sampling noise
The switch may be sized differently,
the switch’s on resistance value may differ,
the on resistance value may change with Vin levels,
but voltage noise power of sampled value in cap is
kT/C