Basic%20Concepts%20of%20Electronics

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Chapter 2

• Basic Concepts of Electronics

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(a)
(b)
Figure 2.1 Electric current within a conductor.
(a) Random movement of electrons generates no
current. (b) A net flow of electrons generated by
an external force.
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Figure 2.2 A model of a straight wire of length l
and cross-sectional area A. A potential
difference of Vb Va is maintained across the
conductor, setting up an electric field E. This
electric field produces a current that is
proportional to the potential difference.
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Figure 2.3 The colored bands that are found on a
resistor can be used to determine its resistance.
The first and second bands of the resistor give
the first two digits of the resistance, and the
third band is the multiplier which represents the
power of ten of the resistance value. The final
band indicates what tolerance value (in ) the
resistor possesses. The resistance value written
in equation form is AB?10C ? D.
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Color Number Tolerance ()
Black 0
Brown 1
Red 2
Orange 3
Yellow 4
Green 5
Blue 6
Violet 7
Gray 8
White 9
Gold 1 5
Silver 2 10
Colorless 20
Table 2.1 The color code for resistors. Each
color can indicate a first or second digit, a
multiplier, or, in a few cases, a tolerance
value.
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(a)
Figure 2.4 (a) The voltage drop created by an
element has the polarity of to in the
direction of current flow. (b) Kirchhoffs
voltage law.
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I 9 A
Figure 2.5 (a) Kirchhoffs current law states
that the sum of the currents entering a node is
0. (b) Two currents entering and one negative
entering, or leaving.
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Figure 2.6 Kirchhoffs current law example.
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Figure 2.7 Example of nodal analysis.
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Figure 2.8 The 1 mV signal from the
electrocardiogram is attenuated by the resistive
divider formed by the 100 k? skin resistance and
the 1 M? input resistance of the oscilloscope.
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Figure 2.9 A potentiometer is a three-terminal
resistor with an adjustable sliding contact shown
by the arrow. The input signal vi is attenuated
by the potentiometer to yield an adjustable
smaller voltage vo.
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Figure 2.10 (a) When a shunt resistor, Rp, is
placed in parallel with a galvanometer, the
device can be used as an ammeter. (b) When a
resistor, Rs, is connected in series with the
galvanometer, it can be used as a voltmeter.
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Figure 2.11 A circuit diagram for a Wheatstone
bridge. The circuit is often used to measure an
unknown resistance Rx, when the three other
resistances are known. When the bridge is
balanced, no current passes from node a to node
b.
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Figure 2.12 (a) Capacitor current changes as the
derivative of the voltage (b) Symbol of the
capacitor.
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Figure 2.13 Diagram of a parallel plate
capacitor. The component consists of two parallel
plates of area A separated by a distance d. When
charged, the plates carry equal charges of
opposite sign.
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Figure 2.14 (a) A series combination of two
capacitors. (b) A parallel combination of two
capacitors.
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Figure 2.15 (a) Inductor voltage changes as the
derivative of the current. (b) Symbol of the
inductor.
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Figure 2.16 Simple inductor circuit.
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(a)
Figure 2.17 (a) Simple RC circuit with v (0) on
capacitor at time t 0. (b) Normalized voltage
across the capacitor for t ? 0 (normalized means
the largest value is 1).
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(a)
Figure 2.18 (a) Series RC circuit with voltage
step input at time 0. (b) Normalized voltage
across the capacitor.
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Figure 2.19 Plot of vo for Example 2.8
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A amplitude of sine wave
f frequency of sine wave in hertz (Hz)
? angular frequency of sine wave in radians per
second
? phase angle of sine wave in radians
T 1/f (period in seconds)
Figure 2.20 One period, T, of the sine and cosine
waveforms.
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Figure 2.21 Sinusoidal waveforms with different
frequencies.
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Figure 2.22 Sinusoidal waveforms with 0º phase
angle (solid) and 180º phase angle (dashed).
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Figure 2.23 Plots of the current and voltage as a
function of time. (a) With a resistor both the
current and the voltage vary as sin(?t), the
current is in phase with the voltage, meaning
that when the current is at a maximum, the
voltage is also. (b) For an inductor, the current
lags behind the voltage 90?. (c) For a capacitor,
the current lead the voltage by 90?.
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(a)
(b)
Figure 2.24 (a) Series circuit. (b) Parallel
circuit. (c) Single impedance equivalent.
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Figure 2.25 (a) Equivalent circuit for op amp.
(b) Symbol of op amp. Many times V and V are
omitted in the op amp symbol, but it is
understood that they are present.
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From Ohms law
Figure 2.26 An inverting amplifier. The gain of
the circuit is Rf/Ri
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Figure 2.27 Inverter circuit attached to a
generator that contains an internal resistance.
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Figure 2.28 (a) A noninverting amplifier, which
also depends on the ratio of the two resistors.
(b) A follower, or buffer, with unity gain.
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Figure 2.29 The gain of the noninverting
amplifier is not affected by the addition of the
impedance Rs due to the generator.
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Figure 2.30 A differential amplifier uses two
active inputs and a common connection.
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Figure 2.31 Differential amplifier attached to a
common mode voltage that contains varying
impedances. Adding buffers ensure that
fluctuations in Rs does not affect the gain.
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Figure 2.32 Differential amplifier for Example
2.13.
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Figure 2.33 (a) A comparator. (b) The
inputoutput characteristic of the comparator in
(a).
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Figure 2.34 Heart beat detector uses a comparator
to determine when the R wave exceeds a threshold.
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Figure 2.35 The typical op amp open loop gain is
much larger, but less constant, than the circuit
gain. However the in circuit bandwidth is larger
than the open loop bandwidth.
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(a)
(b)
Figure 2.36 (a) Low-pass filter. (b) High-pass
filter.
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(c)
(d)
Figure 2.36 (c) Bandpass filter. (d) Bandstop
filter. (PB denotes passband)
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(a)
Figure 2.37 Low-pass filter. (a) RC circuit. (b)
RL circuit.
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(a)
Figure 2.38 High-pass filter. (a) RC circuit. (b)
RL circuit.
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Figure 2.39 A low-pass filter and a high-pass
filter are cascaded to make a bandpass filter.
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Figure 2.40 A square wave of period T oscillates
between two values.
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(a)
(b)
(c)
Figure 2.41 The 555 timer (a) Pinout for the 555
timer IC. (b) A popular circuit that utilizes a
555 timer and four external components creates a
square wave with duty cycle gt 50. (c) The output
from the 555 timer circuit shown in (b).
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Figure 2.42 The ideal static behavior of a 3-bit
DAC. For each digital string, there is a unique
analog output.
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Figure 2.43 A 3-bit voltage scaling DAC
converter.
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Figure 2.44 Converting characteristic of 3-bit
ADC converter.
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Figure 2.45 Block diagram of a typical successive
approximation ADC.
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Figure 2.46 The possible conversion paths of a
3-bit successive approximation ADC.
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(a)
Figure 2.47 (a) Continuous signal. (b) Sampled
sequence of the signal in (a) with a sampling
period of 0.2 s.
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(a)
Figure 2.48 (a) Spectrum of original signal. (b)
Spectrum of sampling function. (c) Spectrum of
sampled signal. (d) Low-pass filter for
reconstruction. (e) Reconstructed signal, which
is the same as the original signal.
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Figure 2.49 General block diagram of a
microcomputer system (arrows represent the data
flow direction).
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Figure 2.50 Three levels of software separate the
hardware of microcomputer from the real problem.
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Figure 2.51 Sketch for cathode ray tube (CRT).
There are two pairs of electrodes to control the
deflection of the electron, but only one pair is
shown.