Lecture06_Noise_Analysis_2up

Lecture06_Noise_Analysis_2up - EECS240 Spring 2008 Lecture...

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EECS240 – Spring 2008 Lecture 6: Noise Analysis Techniques Elad Alon Dept. of EECS EECS240 Lecture 6 2 Noise Variance in a Real Circuit: Sample and Hold Noise on the capacitor: So effective bandwidth is: () 2 2 22 0 1 4 1 on B B oT on vf k T R sRC kT vv f d f C = + →= = 4 1 42 B B o kTR f C f f RC π ∆= →∆ = =
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EECS240 Lecture 6 3 SPICE Verification EECS240 Lecture 6 4 Useful Integrals 2 2 2 2 0 2 1 1 4 1 oo z z s Q df ss Q ωω ω + ⎛⎞ =+ ⎜⎟ ⎝⎠ ++ 2 0 1 14 o o s df = + 22 00 1 4 11 s Q df df QQ ∞∞ == ∫∫
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EECS240 Lecture 6 5 SC Resistor Noise Spectrum S y (f) C R sw 4k B TR sw f s () C T k df f S f T C R T a fT e e f C T k f S r B y s sw a a s r B y s f = = = = + = 2 0 2 2 ) ( 1 and T 2 cos 1 1 1 2 ) ( τ π 0 0.1 0.2 0.3 0.4 0.5 -4 -3 -2 -1 0 1 2 3 4 Normalized Fr equency f/ f s Normalized Noise Density S(f)/(2kT/C) T/ τ = 1 τ = 3 • Noise essentially white for T/ τ > 3 • Settling constraints ensure that this condition is usually met in practice •N o t e : This is the noise density of an SC resistor only. The noise density from an SC filter is usually not white. EECS240 Lecture 6 6 Periodic Noise Analysis PSS pss period=100n maxacfreq=1.5G errpreset=conservative PNOISE ( Vrc_hold 0 ) pnoise start=0 stop=20M lin=500 maxsideband=10 ZOH1 T = 100ns S1 R 100kOhm C 1pF PNOISE Analysis sweep from 0 to 20.01M (1037 steps) PNOISE1 Netlist ahdl_include "zoh.def" Vclk 100ns Vrc Vrc_hold Sampling Noise from SC S/H C1 1pF
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Lecture06_Noise_Analysis_2up - EECS240 Spring 2008 Lecture...

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