ELECTRIC CIRCUIT THEORY WAED 2

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ELECTRIC CIRCUIT THEORYWAED 2

• Paul Tobin
• DIT

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Transfer functions

• A potential divider circuit

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Transfer functions

• The Voltage function for this potential divider
  circuit is

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• Low-pass CR filter

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The voltage transfer function is the output
voltage divided by the input voltage
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Brief visit to the complex numbers world

• Z A jB.

The magnitude of this vector is
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The magnitude of the TF is

• The frequency for which the transfer function has
  a value of 0.5, is called the cut-off frequency

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The cut-off frequency is
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Bode plotting estimates the amplitudeand phase
response two-port networks using straight-line
segments.

• The asymptotic straight lines may represent the
  actual response for a two-port network

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Bode plotting terms

• A constant term K which does not change with
  frequency,
• A (1j??) n term, and
• A j?? term.

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Decibels
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Evaluate the transfer function by plotting each
part of the TF separately. Consider the value of
the TF at two frequencies a decade below the
cut-off frequency, ?c and a decade above ?c
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Asymptotic plotting
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Asymptotic plotting
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The actual and asymptotic response
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Part (a) A decade below fc
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Complete asymptotic response
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