LECT các loại động cơ điện một chiều hay sử dụng
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Lecture 18
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Op-Amps
• Op-Amps is a low-cost and
versatile IC consisting of many
internal transistors, resistors,
and capacitors.
• Amplifiers
• Integrators
•Summers
• Differentiators
•Comparators
• Active filters
Dual Op-Amps (LM358 )
Require external power
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Two Rules for Op-Amp Circuits
• There is no current
flow through the op-
amps input terminal.
(I
oa
= 0 )
• The voltage drop
across the input
terminals is zero.
(V
oa
= 0 )
output
-
+
Inverting
Input
Non-Inverting
Input
Ioa = 0V
oa
= 0
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Amplifiers
• Inverting Amplifier
• Non-Inverting Amplifier
• Summing Amplifier
• Integrator Amplifier
• Differentiator Amplifier
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Inverting Amplifier
•Gain =
i
o
V
V
= -
i
f
R
R
R
i
R
f
V
o
V
i
-
+
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Non-Inverting Amplifier
• Gain =
i
o
V
V
= 1+
i
f
R
R
R
i
R
f
V
o
V
i
-
+
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Summing Amplifier
2
2
1
1
V
R
R
V
R
R
V
ff
o
−−=
R
1
R
f
V
o
V
1
-
+
R
2
V
2
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Integrator Amplifier
R
C
f
V
o
V
i
-
+
∫
−=
t
t
io
dVV
0
RC
1
f
τ
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Differentiator Amplifier
-
+
R
f
C
i
V
o
V
i
dt
dV
V
i
o fi
RC−=
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Active Filters
• First-Order Low-Pass Filter
• Second-Order Low-Pass Filter
• First-Order High-Pass Filter
• Second-Order High-Pass Filter
•Notch Filter
• Band-Pass Filter
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Active First-Order Filter
-
+
R
i
R
f
V
o
V
i
C
f
-
+
C
i
R
f
V
o
V
i
C
f
Low-Pass Filter High-Pass Filter
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Active Second-Order Filters
-
+
R
1
C
1
V
o
V
i
R
2
C
2
-
+
R
1
C
1
V
o
V
i
R
2
C
2
Low-Pass Filter
High-Pass Filter
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Notch Filter
• Notch (or band-stop) filters
are useful in measurement
systems containing
undesirable signal of fixed
frequency. It can reduce the
undesirable frequency to a
tolerance level.
-
+
R
R
V
o
V
i
R
R/2
R/2
C
C
-
+
RC
1
s2s
s
)s(V
)s(V
)s(A
0
2
00
2
2
0
2
i
o
n
=ω
ω+ω+
ω+
==
A
n
(s) is transfer function
ω
0
is notch frequency
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Bode Plot of Active Notch Filter
notch frequency
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Band-Pass Filter
• Band-Pass filters
are used when
certain frequencies
of a signal need to
be emphasized
while the rest be
attenuated.
)s(A1
)s(V
)s(V
)s(G
n
i
o
−==
A
n
(s) is the transfer function
of notch filter
Band-Pass Filter
-
+
Notch
Filter
-
+
R
R
R
R
R
V
i
-V
i
V
o
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Bode Plot of Band-Pass Filter
