ABCs of ADCs - Analog-to-Digital Converter Basics (PDF)
ABCs of ADCs - Analog-to-Digital Converter Basics (PDF)
ABCs of ADCs - Analog-to-Digital Converter Basics (PDF)
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Dis<strong>to</strong>rtion vs.. Linearity (8 Bits)LinearVout = (Vin) 1.05SR = 200Mspsfund = 45.0195 MHz2 nd = 90.039 MHz3 rd = 64.9415 MHz4 th = 19.922 MHz5 th = 25.0975 MHz6 th =70.117 MHzVout = (Vin) 1.02Vout = (Vin) 0.9520These FFT plots, made with our WaveVision s<strong>of</strong>tware, shows the dis<strong>to</strong>rtion that results withdifferent amounts and types <strong>of</strong> non-linearity.The <strong>to</strong>p left plot shows the results with a linear transfer function. All dynamic parameters aremaximized.The lower left plot is the result <strong>of</strong> an input <strong>to</strong> output transfer function <strong>of</strong>Output = Input 1.02The <strong>to</strong>p right plot is the result <strong>of</strong> an input <strong>to</strong> output transfer function <strong>of</strong>Output = Input 1.05The bot<strong>to</strong>m right plot results from an input <strong>to</strong> output transfer function <strong>of</strong>Output = Input 0.95At the right <strong>of</strong> the screen capture you see the harmonic frequencies. The output frequency cannever be higher than 1 / 2 the sample rate because <strong>of</strong> aliasing. Note how the harmonicamplitude increases as the exponent in the input <strong>to</strong> output transfer function departs from unity.<strong>ABCs</strong> <strong>of</strong> <strong>ADCs</strong> - Rev 3, June 2006Authored by: Nicholas “Nick” Gray20Copyright © 2003, 2004, 2006 National Semiconduc<strong>to</strong>rCorporationAll rights reserved
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