HO11_214W09_Noise_part1_2pp

HO11_214W09_Noise_part1_2pp - Handout#11 EE 214 Winter 2009...

Info iconThis preview shows pages 1–5. Sign up to view the full content.

View Full Document Right Arrow Icon
Handout #11 EE 214 Winter 2009 Electronic Noise Part I B. Murmann and B. A. Wooley Stanford University Types of Noise ± "Man made noise” or interference noise – Signal coupling – Substrate coupling – Finite power supply rejection – Solutions • Fully differential circuits • Layout techniques ± "Electronic noise" or "device noise" (focus of this handout) Electronic noise or device noise (focus of this handout) – Fundamental • E.g. "thermal noise" caused by random motion of carriers Technology related • "Flicker noise" caused by material defects and "roughness" B. A. Wooley, B. Murmann EE214 Winter 2008-09 2
Background image of page 1

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Significance of Electronic Noise (1) Signal-to-Noise Ratio 2 2 signal signal PV SNR P V =∝ noise noise B. A. Wooley, B. Murmann EE214 Winter 2008-09 3 Significance of Electronic Noise (2) ± The "fidelity" of electronic systems is often determined by their SNR – Examples • Audio systems Imagers cameras Imagers, cameras • Wireless and wireline transceivers ± Electronic noise directly trades with power dissipation and speed ± Noise has become increasingly important in modern technologies with reduced supply voltages – SNR ~ V signal 2 /V noise 2 ~ ( α V DD ) 2 /V noise 2 ± Topics ± How to model noise of circuit components ± How to calculate/simulate the noise performance of a complete circuit – In which circuits and applications does thermal noise matter? B. A. Wooley, B. Murmann EE214 Winter 2008-09 4
Background image of page 2
Ideal Resistor i(t) 1V/1k Ω ± Constant current, independent of time ± Non-physical – In a physical resistor, carriers "randomly" collide with lattice atoms, giving rise to small current variations over time B. A. Wooley, B. Murmann EE214 Winter 2008-09 5 Physical Resistor i(t) 1V/1k Ω ± "Thermal Noise" or "Johnson Noise" – J.B. Johnson, "Thermal Agitation of Electricity in Conductors," Phys. Rev., pp. 97-109, July 1928 For additional references see supplementary handout “Introduction to Noise” by Daniel Cooley ± Can model random current component using a noise current source i n (t) B. A. Wooley, B. Murmann EE214 Winter 2008-09 6
Background image of page 3

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Properties of Thermal Noise ± Present in any conductor ± Independent of DC current flow ± Instantaneous noise value is unpredictable since it is a result of a large number of random, superimposed collisions with relaxation time constants of τ ≅ 0.17ps – Consequences: • Gaussian amplitude distribution • Knowing i n (t) does not help predict i n (t+ Δ t), unless Δ t is on the order of 0.17ps (cannot sample signals this fast) • The power generated by thermal noise is spread up to very high frequencies (1/ τ ≅ 6,000Grad/s) ± The only predictable property of thermal noise is its average power! B. A. Wooley, B. Murmann EE214 Winter 2008-09 7 Average Power ± For a deterministic current signal with period T, the average power is () 2 2 1 T/ av Pi t R d t T = ⋅⋅ 2 ± This definition can be extended to random signals 2 2 1 nn T P lim i t R dt T =⋅ ± Assuming a real, stationary and ergodic random process, we can write 2 →∞ ±
Background image of page 4
Image of page 5
This is the end of the preview. Sign up to access the rest of the document.

This note was uploaded on 08/13/2009 for the course EE EE214 taught by Professor Borismurmann during the Winter '08 term at Stratford.

Page1 / 14

HO11_214W09_Noise_part1_2pp - Handout#11 EE 214 Winter 2009...

This preview shows document pages 1 - 5. Sign up to view the full document.

View Full Document Right Arrow Icon
Ask a homework question - tutors are online