REVIEW-Bode Plots for Op Amps

# REVIEW-Bode Plots for Op Amps - THINGS YOU SHOULD KNOW...

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Unformatted text preview: THINGS YOU SHOULD KNOW ABOUT BODE PLOTS FOR ACTIVE OP-AMP CIRCUITS (Lecture 39) 1. Convert circuit to phasors and write transfer function. 2. Decibels 3. How to plot term 20log 10 1 + j ¡ RC . 4. Cutoff frequency and 3-db point. PAGE LOWPASS FILTERS 2-5 HIGHPASS FILTERS 6-10 MORE COMPLEX FILTERS 11-14 ENGR 210 REVIEW Bode Plots: Op-Amp Circuits Page 1 ENGR 210 REVIEW Bode Plots: Op-Amp Circuits Page 2 ENGR 210 REVIEW Bode Plots: Op-Amp Circuits Page 3 12-4 We can evaluate the tranfer function using the formula for the gain of an OP AMP amplifier and recognizing that the 5nF capacitor and the 100kΩ resistor are in parallel. T V j ω ( ) = − Z 2 Z 1 = − 1 j ω C ||10 5 10 4 = − 1 j ω C 10 5 1 j ω C + 10 5 10 4 = − 10 5 10 4 1 j ω C 1 j ω C + 10 5 = − 10 1 1 + j ω C 10 5 Substituting in the value of C gives T V j ω ( ) = − 10 1 1 + j ω 5 × 10 − 9 ( ) 10 5 = − 10 1 1 + j ω 5 × 10 − 4 ( ) (a) Evaluating this expression at ω = 0 gives T V ( ) = − 10 ; This can also be evaluated as ω → ∞ to give T V j ∞ ( ) = 0 ....
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## This document was uploaded on 04/18/2011.

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REVIEW-Bode Plots for Op Amps - THINGS YOU SHOULD KNOW...

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