CHAPTERS 5

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CHAPTERS 5 6

• NETWORKS 1 0909201-01
• 5 October 2004 Lecture 6
• ROWAN UNIVERSITY
• College of Engineering
• Dr Peter Mark Jansson, PP PE
• DEPARTMENT OF ELECTRICAL COMPUTER ENGINEERING
• Autumn Semester 2004 Quarter One

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admin

• TOMORROW
• Wednesday - test on chapters 3-6.4
• Rowan Auditorium 9.25AM 1PM
• todays lab Thevenin equivalent circuits
• Do we want a review? Today 5PM?

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networks I

• Todays learning objectives
• review
• supermeshes
• new methods for reducing complex circuits to
  simpler forms
• Thévenins equivalent
• Nortons equivalent
• maximum power transfer
• introduce operational amplifiers
• the ideal op-amp and nodal analysis

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Supermesh? Remember Supernode

• A Supernode consists of two nodes connected by
  an independent or dependent voltage source.
• A Supermesh one larger mesh that is created
  from two meshes that have an independent or
  dependent _______ source in common.

current
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Supermesh example

• see page 125
• write KVL of supermesh, note it does not
  include interior resistor or common current
  source.

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new concepts from ch. 5

• electric power for cities - DONE
• source transformations - DONE
• superposition principle - DONE
• Thévenins theorem - DONE
• Nortons theorem - DONE
• maximum power transfer - finish

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Thévenin equivalent circuit
Rt
a
?
_
vt or voc
b
?
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Thévenin method

• If circuit contains resistors and ind. sources
• Connect open circuit between a and b. Find voc by
  ST or..
• Deactivate source(s), calc. Rt by circuit
  reduction
• If circuit has resistors and ind. dep. sources
• Connect open circuit between a and b. Find voc
• Connect short circuit across a and b. Find isc
• Connect 1-A current source from b to a. Find vab
• NOTE Rt vab / 1 or Rt voc / isc
• If circuit has resistors and only dep. sources
• Note that voc 0
• Connect 1-A current source from b to a. Find vab
• NOTE Rt vab / 1

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Another HW example

• see HW problem 5.5-3
• page 184
• Step one on board
• Step two current source and two resistors
• Learning Check 1 name value of current source
  and values of the two Rp

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Norton equivalent circuit

a
?
isc
Rn Rt
Va-b voc Rnisc

b
?
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Norton method

• If circuit contains resistors and ind. sources
• First attempt Source Transformation
• If necc., connect short circuit between a and b.
  Find isc
• Deactivate ind. source(s), calc. Rn Rt by
  circuit reduction
• If circuit has resistors and ind. dep. sources
• Connect open circuit between a and b. Find voc
  vab
• Connect short circuit across a and b. Find isc
• Connect 1-A current source from b to a. Find vab
• NOTE Rn Rt vab / 1 or Rn Rt voc / isc
• If circuit has resistors and only dep. sources
• Note that isc 0
• Connect 1-A current source from b to a. Find vab
• NOTE Rn Rt vab / 1

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maximum power transfer theorem

• Remember
• maximum power delivered by a source represented
  by its Thevenin equivalent circuit is attained
  when the load RL is equal to the Thevenin
  resistance Rt

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efficiency of power transfer

• how do we calculate it for an electronic
  circuit?

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HW example

• see HW problem 5.7-5
• Show Rt as Learning Check 2
• Show Va-b (or Voc) as LC 3
• Show max power as LC 4

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new concepts from ch. 5

• electric power for cities - DONE
• source transformations - DONE
• superposition principle - DONE
• Thévenins theorem - DONE
• Nortons theorem - DONE
• maximum power transfer - DONE

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ONE LAST Superposition.

• HW 5.4-5
• Consider 8V only (open 2A source)
• Write KVL of supermesh, and i8V for LC5
• Consider 2A only (short 8V source)
• Write KVL of supermesh, and i2A for LC6

Finally write i TOTAL i8V i2A for LC7
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new concepts from ch. 6

• operational amplifier
• the ideal operational amplifier
• nodal analysis of circuits containing ideal op
  amps
• design using op amps
• characteristics of practical op amps

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definition of an OP-AMP

• The Op-Amp is an active element with a high
  gain that is designed to be used with other
  circuit elements to perform a signal processing
  operation.
• It requires power supplies, sometimes a single
  supply, sometimes positive and negative supplies.
• It has two inputs and a single output.

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OP-AMP symbol and connections
INVERTING INPUT NODE
v1
OUTPUT NODE
i1
vo
io
i2
v2
POSITIVE POWER SUPPLY
NON-INVERTING INPUT NODE
NEGATIVE POWER SUPPLY
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THE OP-AMPFUNDAMENTAL CHARACTERISTICS
INVERTING INPUT NODE
_
Ri
v1
OUTPUT NODE
i1
vo
io
Ro
i2
v2
NON-INVERTING INPUT NODE
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THE IDEAL OP-AMPFUNDAMENTAL CHARACTERISTICS
Ri
Ro
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THE INVERTING OP-AMP
Rf
Ri
node a
v1
i1
vo
io
vs
i2
v2
1. Write Ideal OpAmp equations. 2. Write KCL at
node a. 3. Solve for vo/vs
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THE INVERTING OP-AMP
Rf
Ri
node a
v1
i1
vo
io
vs
i2
v2
At node a
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THE NON-INVERTING OP-AMP
Rf
Ri
node a
v1
i1
vo
io
i2
v2

vs
At node a
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HW examples

• see HW problems.
• problem 6.4-1, page 228
• problem 6.4-2, page 228
• problem 6.4-6, page 229

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Op Amp circuit types

• for K lt 0
• for K gt 1
• for K 1
• special case 0 lt K lt 1

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What you need to know

• Parameters of an Ideal Op Amp
• Types of Amplification Gain (K) vs. Which nodes
  and Amps circuits are needed to achieve same
• How to identify which type of circuit is in use
  (effect)
• How to solve simple Op Amp problems