EEL6935-F10-HLec02-opamps-2spp

EEL6935-F10-HLec02-opamps-2spp - Lecture 2: Simple...

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1 Lecture 2: Simple Amplifier Review Amplifier Gain and DC bias Amplifier Models STC circuits Amplifier frequency response Amplifier Amplifier Circuit Symbol To amplify means to multiply by constant V o =A v x V i Av is the gain Vo cannot increase indefinitely
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2 Amplifier with supply rails To explicitly show the supply voltages, V CC and V EE are shown. In some cases, V EE is zero. Linear and non-linear regions of operation Amplifier Gain and DC Bias V i (t)=V I +v i (t) signal DC bias Total instantaneous
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3 Amplifier Gain Voltage Gain: A v = (dB) 20log A v dB Current Gain : A i = (dB) 20log A i dB Power Gain: A p =A v A I (dB) 10log A p dB I o V V I o i i  ) ( ) ( 2 1 ) ( dB A dB A dB A I V P Note: multiplication of two numbers is equivalent to adding their logarithms A few words about dB When is the Gain in dB a negative number? – Inverting amplifier (180 degrees phase difference between input and output) – Or when the amplifier is attenuating dB is unitless: – 20log (V/V) or 20log (I/I) or 10log(W/W) Find the log of 0.1, 1, 10 , 100 -10dB, 0dB, 20dB, 40dB If the gain is -6dB, what is the gain in V/V? – -6dB=20log(x) -> x=10 -6/20 = 0.5 If gain is -3dB, what is the gain in V/V? – -6dB=20log(x) -> x=10 -3/20 = 0.707 (i.e. 3 dB BW, Half Power). Why? 0.707 2 = 0.5 – Power = 10 log (p), Voltage = 20 log (v) but power prop to voltage squared.
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This note was uploaded on 01/17/2011 for the course ECE Biomedical taught by Professor Dr.rizwanbashirullah during the Fall '10 term at University of Florida.

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EEL6935-F10-HLec02-opamps-2spp - Lecture 2: Simple...

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