Electrical Components and Circuits

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Chapter 2.
Electrical Components and Circuits
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Electric current the motion of a charge
through a medium. Electric units the unit of
charge (or quantity of electricity) C(coulomb)
? 0.001111800g of silver ion ? Charge for
reduction to silver metal. 1Faraday 9.649 x 104
coulombs 1Faraday Deposition of Ag 107.868g of
1 gram equivalent ? (6.02 x 1023 charged
particle), I dQ/dt (Q charge, A ampere)  
Electrical Components
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• 2A Direct-Current Circuits and Measurements
• - Direct current ??? ??? ??
• Alternating current ??? ????? ???? ?.
• 2A-1 Laws of Electricity
• ? ? ??? electrical potential (V) ??? ? ??? ??
  ??? 1?? ??? ????? ? ?.
• V volt ? joule/conlomb (W/Q V) (IR)
• R ohm ? R? ?? O(R ?l/A) ? Ohm's
  law
• G ??? ??(electrical conductance) O-1, S
• I Ampere
• P Electrical power. joules/sec, W
• P dw/dt VdQ/dt VI
• P (IR)I I2R. joule's law

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Kirchhoff's Laws - Current low the algebraic
sum of currents around any point in a circuit is
zero. -Voltage low the algebraic sum of the
voltages around a closed electrical loop is
zero.
Power Law P IV P I2R V2/R
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2A-2 Direct-Current Circuits

1. Series circuits

Fig 2-1. A battery, a switch, three resistors
in series.
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? ? D?? kirchhoff's law ?? I4 - I3 0 or I4
I3 , I3 I2 at point C. the current is the
same at all points I I1 I2 I3 I4 ?
Voltage low V - V3 - V2 - V1 0 or V V1
V2 V3 by ohm's law V 1(R1 R2 R3)
IReq ? Req R1 R2 R3   IR1 V1 , V2
IR2 , V3 IR3


V1 I1 R1 IR1
(2-9)
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Voltage dividers Fig 2-3 a ? series connection
of resistor ? discrete increment
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- Potentiometer continuously variable
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2) Parallel Circuits Resistors in parallel at
point A
Kirchhoff's current law to point A I1 I2
I3 - It 0 It I1 I2 I3
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- Parallel resistances create a current divider.
I1 V/R1 1/R1 G1 Rp
G1 --- ----- ----- --- or I1 It ---
It --- It V/Rp 1/Rp Gp
R1 Gp
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(Ex. 2-1)
Calculate a) the total resistance, b) the
current from the battery, c) the current present
in each of the resistors, and d) the potential
drop across each of the resistors.
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• 1 1 1
• ( --- --- ) ---
• R2 R3 R2,3
• 1 1 1 3
• --- --- --- --- R2,3 13.3O
• R 20 40 40

V
15 b) The current V IR I --- -----
0.67A
Rs 22.3 c) V V1 V2 V3 V1 I1R1
6.03 I I2 I3 ??? 9.0
V1 15 x ------------ 6.0V
(9.0 13.3)
13.3 V2 V3 V2,3 15 x ------ 9.0V
22.3 d) R1?? I1 I
0.67A I2 9.0/20 0.45A I3 9.0/40
0.22A
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2A-3 Direct Current, Voltage, and Resistance
Measurements
Digital Volmeters and Multimeters DArsonval
moving-coil meter ? Digital
Voltmeters and Multimeters. Power Source,
display, A/D converter
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The Loading Error in Potential Measurements
The Loading Error in Current Measurements
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See equations 2-19 and 2-20
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2B Alternating current Circuits
Alternating voltage and current ??? ?? ??? ???
???? ??? ??? ?? ???? ?? ?? ??. ( the simplest
alternating waveform is sine-wave volt or
current.) - Period (Tp) The time required for
the completion of one cycle - Cycle one complete
revolution - Frequency(f) HZ time number of
cycles per second
f 1/tp (2-21)
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Sinusoidal signals
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2B-1 Sinusoidal Signals
The AC produced by rotation of a coil in a
magnetic field. A pure sine wave ? ??? ???? ??
??(????) IP? vector? ??. (??? Ip amplitude.)  
?? t ?? 2p radian ? ??? ?? ? ? ? 2p/tp 2pf
Any time t?? instantaneous value ? Vpsin
?t Vp maximum or peak voltage the amplitude
?? ?? ? Ip sin ?t Ip sin 2pft ?? ??
v Vp sin ?t Vp sin 2pft Out of phase by
90o Phase difference phase angle(f) ??? ? Ip
sin(?t f) Ip sin(2pft f)
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(rms current voltage) DC, AC? ???? ? ??? ??
???? ???? Joule heat DC the effective value of
a sinusoidal, current Report, heating effect of
AC is calculated by averaging I2R losses even
complete cycle
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1 Hz ?? ?? ??? ??? ?? ohm??
square wave ??? 1.00 ??? 1.00 sine
wave ??? 1.11 ??? 1.41 ??? ???
1.15 ??? 1.73
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2B-2 Reactance in Electrical Circuits
Reactance - capacitance capacitor
inductance inductor Use ? converting
alternating current to DC or the converse
? discriminating among signals of different
frequencies or separating ac dc
signals. Capacitors ?? a pair of conductors
separated by a thin layer of a dielectric
substance
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Position 1
Position 2
Figure 2-8. (a) A series RC circuit. Time
response of circuit when switch S is (b) in
position 1 and (c) in position 2.
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2B-3 Capacitors and Capacitance 1) Capacitance ?
a momentary current ? current ceases ? to be
changed ? switch? 2? discharge.   Capacitor ? ?
? ???? switch off ?? ??? ?? The quantity of
electricity Q ? ? ??, ??, ??, ??? ? ????? ?? ??
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1 Faraday 1 V? ???? ?? ???? ??? ??? ??? 1 C? ??
capacitance. ( µF, PF)
V 1/C ?idt 1/C? Ip sin wt dt
-1/wc Ip cos wt 1/wc Ip
sin(wt - p/2) ? Vp 1/wc Ip,
V (1/wc) I 1/wc Xc ?
capacitive reactance ?? O
Xc -1/wc, V XcI
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Rate of current changes in an RC circuit By
Kirchhoff ? voltage law
Vi Vc VR
Vi constant
Vi q/C iR
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Rate of Voltage Change in an RC circuit
use Ohms law to eq. 2-35
Phase relations between current and voltage in an
RC circuit
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Rate of Current Potential Change across RL
circuit. RC circuit? ??? ???? ??
VR Vi( I - e-tR/L )
VL Vi e-tR/L
L/R time constant
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2B-4 Response of Series RC Circuits to Sinusoidal
Inputs Response of series RC RL circuits to
sinusoidal inputs signal (Vs)
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Ip
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(1/?C Xc)
At sufficiently high frequencies capacitance, f
become negligible I v are in phase. 1/?C? ??
R? ?? ?? ?. ? ??? ? ?? At very low
frequencies, the phase angle p/2
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Voltage, current and phase Relationships for
series RL circuit
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Figure 2-9
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Capacitive Inductive Reactance impedance
Xc 1/wC 1/2pfC
XL wL
2pfL Impedance Z ?????? ??? ??? ??? ?(????? ???
??) At, RC circuit
Z vR2 Xc2
Z vR2 XL2
Ip Vp/Z
??? ??? ? frequency dependent ? current?
voltage ??? phase difference
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Figure 2-10
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ltVector diagrams for Reactive Circuitsgt V? ???
90??. at capacitance V? ??? 90???. at
inductance Z vR2 (XL - Xc)2 Z vR2 Xc2 ,
f -arctan Xc/R Z vR2 XL2 , f -arctan
XL/R Z vR2 (XL Xc)2 f -arctan (XL Xc) /
R (XL gt Xc ? ??) ex) ? peak current ?
voltage drop Z v(50)2 (40 - 20)2 53.8O Ip
10 v/53.8 0.186A Vc 0.186 x 20
3.7V VR 0.186 x 50 9.3V VL 0.186 x
40 7.4V
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2B-5 Filters Based on RC Circuits High-pass
Low-Pass Filters RC RL circuits ? low f
component? ??? ?? high-f signals? ??? ?? filter?
?? (low pass filter) or ?? ??. ? RC circuit??
high-pass filter Vo across the resistor R
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(a) high pass filter and (b)low-Pass Filters
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Low pass filter
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2B-6 The Response of RC Circuits to Pulsed
Inputs ltResonant Circuitsgt impedance Z? ?? ? XL
Xc ? ? ?? I E/Z E/R ? the condition
of Resonance resonant frequency fo 1/2pfoC
2pfoL ? fo 1/2pvLC ex) (Vp)i 15.0 V (peak
voltage), L 100mH, R 20O, C 1.200µF.
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Figure 2-13
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2B-7 Alternating Current, Voltage, and Impedance
Measurements Parallel Resonance Filters
Xc XL fo 1/2pvLC Z of the
parallel circuit Z
vR2 (XLXc/Xc-XL)2 At parallel circuit at
resonance ? Z? ?? ? maximum voltage drop ? ?
tank circuit   Behavior of RC Circuits with
pulsed inputs RC ??? pulse ? ? various form
(with of pulse time const) ??? ??? ?? Simple
Electrical Measurements Galvanometers ? DC? ??,
?? ?? ?? the current in duceol motion of a coil
suspended in a yixed magnetic yiedd. ? D'arsonval
movement or coil. He Ayrton Shunt to vary the
range of a galvanometers p29. ?? ?? ?
measurement of current and voltage.
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Semiconductor Device
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• 2C Semiconductors and Semiconductor Devices
• Semiconductors
• Electronic circuits contain one or more nonlinear
  devices such as transistors, semiconductor
  diodes, and vacuum or gas-filled tubes.
• Nonlinear components rectification (from ac to
  dc ) amplitude modulation or frequency modulation
  vacuum tube ? Semiconductor based diodes and
  transistors ? integrated circuits (Tr, R, C
  conductor)
• -Semiconductor ?? low cost, low power
  consumption, small heat generation, long life and
  compactness.

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• 2C-1 Properties of silicon germanium
  semiconductors.
• Sufficient thermal agitation occurs at room temp.
  to liberate an occasional electron from its
  bonded state, leaving it free to more through the
  crystal lattice and thus to conduct electricity.
• Hole positively charged region.
• -Electron negatively charged region.
• -Hole electron ? ???? ??.
• -Doping of arsenic or antimony (Group ?) ? n type
• of indium or gallium (Group ?) ? p
  type
• Positive holes are less mobile them free
  electrons.
• Conductivity of n type gtconductivity of p type.
•  

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2C-2 . Semiconductor Diodes Pn junction motion ?
diode is a nonlinear device that has greater
conductance in one direction than in another.

Figure 2-15 A pn junction diode (c) forward -
bias (d) reverse - bias ? depletion layer ??
conductance 10-610-8
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Figure 2-16 I - V cures for semiconductor Diodes
The voltage at which the sharp increase in
current occurs under reverse bias is called the
Zener breakdown voltage.
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2C-3 Transistors Amplifying device -Bipolar
-Field effect transistor. ? Bipolar Tr. pnp,
npn tr.
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Figure 2-17.
The mechanism of amplification with a bipolar
transistor. pnp on ? n layer 0.02mm thickness,
pgtgtn layer. (??? ??), ?The concentration of
holes in p gtgt that of electrons in n layer
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Figure 2-18.
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? P-type emitter junction ?? hole ?? ? ??? hole ?
very thin n-type base ? ?? - electron ? ?? (base
current IB??) ? ???? hole ? base? ?? drift ??
collector junction ?? attracting ? ??? power
supply??? ?? electron ? combined ?? ?? ??
(Ic) The no of current carrying holes is a fixed
multiple of the number of electrons supplied by
the input base current.
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Field Effect Transistors (FET) FET - The
insulated gate field effect transistor.
?1091014 ? ? imput impedence ? MOSFET (metal
oxide semiconductor FET) n- chanel MOSFET The
gate is a cylindrical p-type semiconductor
surrounding a center core of n -doped material
called the channel. Two isolated n regions are
formed in a p-type substrate. ?? n.p regions ?
silicon dioxide? insulating
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Figure 2-19.
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(n-channel junction FET) current enhancement in
brought about by application of a positive
potential to the gate Gate ? " induce -
substrate channel below the layer of
SiO2 Depletion mode ?in the absence of a gate
voltage reverse bias is applied to the gate the
supply of electrons in the channel is depleted. ?
channel ?? ???????. The width of the reverse
biased gate junction determined (the wide of the
channel and consequently). The magnitude of the
current between source and drain.
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2D Power Supplies and Regulators most ps contains
a voltage regulator.
Figure 2-20.
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2D-1 Transformers VX 115 X N2/N1 N2 and N1 are
the no of turns in the secondary and primary
coils.
2D-2 Rectifiers ?Half wave rectifier ?Full wave
rectifier ?bridge rectifier ???? ? ??
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Figure 2-21.
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D2, D3 ? conduct on the alternate D4 and D1
conduct Since two diodes are in series with the
load, the output voltage is reduced by twice the
diode drop.
Figure 2-22.
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2D-2 Rectifiers and Filters
Figure 2-23.
In order to minimize the current fluctuations. L
section filter S ? ?? C? ?? ??. ? peak to peak
ripple can be reduced.
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2D-3 Voltage Regulators
Figure 2-24.
Zener diode breakdown condition ??? ??. Under
breakdown condition, a current change of 20 to 30
mA may result from a potential change of 0.1 V or
less.
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2E Readout Devices
Figure 2-25. Basic analog oscilloscope component
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2E-1 Oscilloscopes Cathode-Ray Tubes
Horizontal and vertical Control Plates.
Trigger Control.
Figure 2-26. Schematic of a CRT
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2E-2 Recorders
Figure 2-27. Schematic of self-balancing
recording potentiometer
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2E-3 Alphanumeric Displays
2E-4 Computers