ENGR 101
Capacitors
The voltage/current relationship for a capacitor is
Introduction to Electrical Engineering
Session 3
i C
dv
dt
That's right, capacitors know calculus!
Outline
Capacitors and Inductors
Diodes and Transistors
Integrated Circuits and Op Amps
The units for capacitance (C) are Farads (F), but a
1 F cap is huge. Typical values in electronic
applications are 1 F (10-6 F) or 1 pF (10-12 F).
Capacitors can be used to build differentiators
and integrators.
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Capacitors
Inductors
Schematic symbol:
Schematic symbol:
Some types of capacitors are polarized and must
be connected properly or they can explode.
Current/voltage relationship:
The units for capacitance (C) are Farads (F), but a
1 F capacitor is huge. Typical values for
electronics applications are 1 F (10-6 F) or 1 pF
(10-12 F).
v
L
di
dt
The units for inductance (L) are Henrys (H).
Typical values for electronics applications are 1
m H (10-3 H) or 1 H (10-6 H).
Not as common as capacitors in electronics
except at radio frequencies.
Capacitors can be used to build differentiators
and integrators and filters.
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4
Filters
Filters
A low pass filter passes through low frequency
voltages while blocking high frequencies.
A high pass filter passes through high frequency
voltages while blocking low frequencies.
VIN
VOUT
VIN
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VOUT
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Diodes
Transistors
Diodes only allow current to flow in one
direction. They act like open circuits when
current tries to low the wrong way.
Transistors, when used as voltage controlled
switches, are the fundamental component in
digital and computer systems.
There are some special purpose diodes. Light
emitting diodes (LEDs) give off light.
Transistors, when used as amplifiers, are the
fundamental component in communication
systems.
Current
Flow
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8
Integrated Circuits
Operational Amplifiers
Integrated circuits (ICs or chips) contain
miniature resistor, diode, and transistor circuits.
Op amps are easy-to-use, off-the-shelf IC
amplifiers. A typical op amp contains about 40
transistors.
Modern microprocessors are ICs with over a
million transistors in a single circuits.
8 7 6 5
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ICs are available for both digital and analog
applications.
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2
+
-
6
4
Schematic Symbol
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1 2 3 4
Drawing of IC
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