EMLAB 1 기초 회로 이론 2014. 9. 1.. EMLAB 2 Contents 1.Basic concepts 2.Resistive circuits...
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Transcript of EMLAB 1 기초 회로 이론 2014. 9. 1.. EMLAB 2 Contents 1.Basic concepts 2.Resistive circuits...
EMLAB
1
기초 회로 이론
2014. 9. 1.
EMLAB
2Contents
1. Basic concepts
2. Resistive circuits
3. Nodal and loop analysis techniques
4. Operational amplifiers
5. Additional analysis techniques
6. Capacitance and inductance
7. First and second order transient circuits
EMLAB
3
Super-computer
Rack-mount computer
motherboard
Printed circuit board
Circuits for modern electronic systems
Example : ATX power supply schematic
EMLAB
4Electronic circuit design flow
System concept
Functional specification
Schematic circuit
Schematic simulation
BOM (Bill of materials)
PCB layout
Test and debugging
EMLAB
5Typical electronic components
EMLAB
6
Basic concepts
EMLAB
7Charges : electrons, nucleus
EMLAB
8Friction charges
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9
Electrons “lost”
Electrons “gained”
Contact
Separation
Generation of friction charges
EMLAB
10
Electrons(-) are absorbed.(+) charges are generated
Electrons(-) are generated. (+) charges are absorbed.
Generation of charges : battery
e2ZnZn 2
234 HNH222NH e
Electrons are generated via electro-chemical reaction.
EMLAB
11
The globe lights up due to the work done by electric current (moving charges).
Steady state current (simple DC circuit)
Current
EMLAB
12Charge transport : microscopic view
Direction of current is de-fined as that of positive charges by convention.
Direction of current
EMLAB
13
dt
dQI I
• Current is electric charges in motion, and is defined as the rate of movement of charges passing a given reference plane.
• In the above figure, current can be measured by counting charges passing through surface S in a unit time.
S
Definition of current
q
EMLAB
14
Positive charges
Negative charges
Charge transport mechanism: drift current
Charges are drifted by electro-magnetic waves.
E
HE
H
EMLAB
15Charge transport : diffusion current
Positive charges are plenty.
Charges in a wire are moved by diffusion and electromagnetic laws.
Charge movement by diffusion
Negative charges are plenty.
Diffusion
Diffusion current is due to density gradi-ent independent of charges.
EMLAB
16Electromotive force
e2ZnZn 2
234 HNH222NH e
Electrons are generated via electro-chemical reaction.
Chemical battery
(reduction)
(oxidation)
EMLAB
17AC(alternating current) generator
Electromotive force is generated by chang-ing magnetic flux (Faraday’s law).
EMLAB
18
Circuit elements
EMLAB
19
Independent sources Dependent sources
Circuit symbols
resistor capacitor inductor transformer
Ground (GND)
EMLAB
20voltage sources
Voltage source
Dry cellLithium ion battery
Lead-acid battery
Switching power supply DC power supply
i-v characteristics
EMLAB
21Analogy between potential energy and voltage level
• Absolute value of voltage is not impor-tant.
• Only voltage difference has physical meaning.
EMLAB
22
• Ground (GND) is used to represent volt-age reference (0 V), arbitrarily.
Ground symbol
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23
current source
current sources
EMLAB
24resistors
11 )()( RtitR
EMLAB
25capacitors
t
0
)(1
)( dttiC
tC
EMLAB
26
)(ti
i-v relation of a capacitor
t
0
)(1
)( dttiC
tC
EMLAB
27inductors
dt
diLtL )(
EMLAB
28i-v relation of an inductor
dt
diLtL )(
)(t
EMLAB
29Passive sign convention
-
)(t
)(ti
A circuit element absorbs power when the current flows into the posi-tive terminal.
)()()( tittp
• For passive devices, the terminal into which current comes becomes a positive terminal.
• For independent sources, current flows out of the posi-tive terminal.
EMLAB
30Example
)(ti
)(t Power is
absorbed
)(ti
)(t
Power is generated
EMLAB
31
Power = 0.1 * 1.5 = 0.15W (absorp-tion)
1.5V
0.1A
0.1A
1.5V1.5V
-0.1A
Power = -0.1 * 1.5 = -0.15W (generation)
Example : passive sign convention
EMLAB
32Power
dttitW
tittp
)()(
)()()(
Power is defined to be the energy dissipated per unit time.
)()()( titdt
dq
dq
dW
dt
dWtp
EMLAB
33
• The sum of the powers absorbed by all elements in an electrical network is zero.
• Another statement of this theorem is that the power supplied in a network is exactly equal to the power absorbed.
Tellegen’s theorem
-36W
54W
-18W
-36W + 54W -18W = 0
EMLAB
34
Given the two diagrams shown in Fig. 1.12, determine whether the element is absorbing or supplying power and how much.
Example 1.2
In Fig. 1.12a the power is P=(2 V)(–4 A)=–8 W. Therefore, the element is supplying power. In Fig. 1.12b, the power is P=(2 V)(–2 A)=–4 W. Therefore, the element issupplying power.
EMLAB
35
We wish to determine the unknown voltage or current in Fig. 1.13.
Example 1.3
In Fig. 1.13a, a power of –20 W indicates that the element is delivering power. Therefore, the current enters the negative terminal (terminal A), and from Eq. (1.3) the voltage is 4 V. Thus, B is the positive terminal, A is the negative terminal, and the voltage between them is 4 V.
In Fig 1.13b, a power of ±40 W indicates that the element is absorbing power and, therefore, the current should enter the positive terminal B. The current thus has a value of –8 A, as shown in the figure.
EMLAB
36
Determine the power supplied by the dependent sources in Fig. E1.4.
(a) Power supplied = 80 W;(b) power supplied = 160 W.
Example E1.4
EMLAB
37Example 1.7
Use Tellegen’s theorem to find the current Io in the network in Fig. 1.19.
-12 + 6Io - 108 - 30 - 32 + 176 = 0
Io = 1A
EMLAB
38
The charge that enters the BOX is shown in Fig. 1.20. Calculate and sketch the current flowing into and the power absorbed by the BOX between 0 and 10 milliseconds.
Example 1.8