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ENGS2613 Intro Electrical Science
Week 7
Dr. George Scheets
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Read 4.13, 5.1 – 5.4
Problems 4.82, 85, & 93; m5.1, 3, &4
Quiz Friday (Find Thevenin Equivalent)
Mini Design Results
Hi = 10, Low = 5, Average = 9.45, Deviation = 0.85
Lowest Figure of Merit
A = 0.51, B = 1.18, C = 0.24, D = 0.30
Norton Equivalent Circuits
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Any 2 terminal
resistive circuit….
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Can be replaced
with …
Fancy Circuit
with
Resistors
&
Voltage and/or
Current sources
Is
… where Vs = Is R
↑
R
Norton Equivalent Circuit
Named after Edward Lawry Norton
1898 – 1983
 American Engineer
Bell Labs
 1926
Proposed Current Source
Equivalent of Thevenin's
Theorem

 Also
derived in 1926
by Hans Myer of Siemens
Source: Wikipedia
Vout as Rload is varied
+
Vs
-
Vout
R
I
Rload
Vs = 1 volt
R = 50 Ω
Iout as Rload is varied
+
Vs
-
Vout
R
I
Rload
Vs = 1 volt
R = 50 Ω
Power Delivered to the Load
+
Vs
-
Vout
R
I
Rload
Source fixed?
Max Load Power occurs
when Source Resistance
R = Load Resistance Rload
Vs = 1 volt
R = 50 Ω
Power = VoutI
Quiz 2B Thevenin Equivalent
+
12.36 V
-
2.181 Ω
To Maximize Power Transfer

Source Resistance Fixed?
 Set

Load Resistance = Source Resistance
Source Resistance Adjustable?
 Want
Source Resistance as small as possible
Active Vs Passive Device
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Passive Device (Resistor)
 Cannot Generate Power
Active Device (Voltage or Current Source)
 Can generate power
 Requires some sort physical or chemical activity
 Converts this to Electrical Power
 Efficiency < 100%
OpAmp (Active Device)
 Absorbs power from a power supply
 Converts this power to another form
 Amplify a weak signal
 Act as "On – Off" electrical switch
Inside a Typical OpAmp