This preview shows pages 1–5. Sign up to view the full content.
This preview has intentionally blurred sections. Sign up to view the full version.
View Full DocumentThis preview has intentionally blurred sections. Sign up to view the full version.
View Full Document
Unformatted text preview: EECS 215 Frequency Response J. Phillips EECS 215 Transfer Function We often want to know how a circuit will respond to changing frequency Transfer function: relates output to input ( ) ( ) ( ) X Y H = ( ) ( ) ( ) gain Voltage = = i o V V H ( ) ( ) ( ) gain Current = = i o I I H ( ) ( ) ( ) Impedance Transfer = = i o I V H ( ) ( ) ( ) Admittance Transfer = = i o V I H J. Phillips EECS 215 Poles And Zeros Separate H( ) into numerator and denominator (Not necessarily input and output) ( ) ( ) ( ) D N H = ( ) zero) to goes (function zero = N Roots of numerator and denominator provide much insight into frequency response ( ) infinite) is (function pole = D For convenience, substitute s = j Frequency response characteristics described by poles and zeros J. Phillips EECS 215 Low Pass RC 0.5 1 1.5 2 x 10 5 0.5 1 Frequency (Hz) M a g n i t u d e 0.5 1 1.5 2 x 10 580604020 Frequency (Hz) P h a s e ( d e g r e e s ) J. Phillips EECS 215 High Pass LC 0.5 1 1.5 2 x 10 5 0.5 1 Frequency (Hz) M a g n i t u d e 0.5 1 1.5 2 x 10 5 20 40 60 80 Frequency (Hz) P h a s e ( d e g r e e s ) J. Phillips EECS 215 Decibels Convenient to describe frequency response on logarithmic scale bels of number log 1 2 10 = = P P G Ratio of two powers For voltage, current, recall relation to power = 1 2 10 log 10 P P G dB dB P P 3 ~ 2 1 2 = dB P P 3 ~ 5 . 1 2 = dB P P 1 2 = = 1 2 10 log 20 V V G dB = 1 2 10 log 20 I I G dB Decibels J. Phillips EECS 215 Bode Plots Convenient and standard technique of plotting frequency response j He H = = H j H + = ln H ln Semilog plots of magnitude (dB) and phase of transfer function Semilog plots are more intuitive, easier to construct H H dB 10 log 20 = Since these are logarithmic, each factor can be...
View
Full
Document
 Winter '08
 Phillips
 Frequency, Volt

Click to edit the document details