1. 기초 회로 이론

2. Contents Basic concepts Resistive circuits
Nodal and loop analysis techniques
Operational amplifiers
Additional analysis techniques
Capacitance and inductance
First and second order transient circuits

3. Circuits for modern electronic systems
Rack-mount computer
Super-computer
motherboard
Printed circuit board
Example : ATX power supply schematic

4. Electronic circuit design flow
System concept
Functional specification
Schematic circuit
Schematic simulation
BOM (Bill of materials)
PCB layout
Test and debugging

5. Typical electronic components

6. Chapter 1. Basic concepts

7. Charges : electrons, nucleus

8. Friction charges

9. Generation of friction charges
Contact
Electrons “lost”
Electrons “gained”
Separation

10. Generation of charges : battery
Electrons(-) are absorbed.
(+) charges are generated
Electrons(-) are generated.
(+) charges are absorbed.
Electrons are generated via electro-chemical reaction.

11. Current Steady state current (simple DC circuit)
The globe lights up due to the work done by electric current (moving charges).

12. Charge transport : microscopic view
Direction of current is defined as that of positive charges by convention.
Direction of current

13. Definition of current
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.

14. Charge transport mechanism: drift current
Positive charges E E
Charges are drifted by electromagnetic waves. H H
Negative charges

15. Charge transport : diffusion current
Charges in a wire are moved by diffusion and electromagnetic laws.
Positive charges are plenty.
Diffusion
Charge movement by diffusion
Diffusion current is due to density gradient independent of charges.
Negative charges are plenty.

16. Electromotive force Chemical battery (reduction) (oxidation)
Electrons are generated via electro-chemical reaction.

17. AC(alternating current) generator
Electromotive force is generated by changing magnetic flux (Faraday’s law).

18. Circuit elements

19. Circuit symbols Independent sources Dependent sources Ground (GND)
resistor
capacitor
inductor
transformer

20. voltage sources Dry cell Lithium ion battery Lead-acid battery
Switching power supply
DC power supply
i-v characteristics
Voltage source

21. Analogy between potential energy and voltage level
Absolute value of voltage is not important.
Only voltage difference has physical meaning.

22. Ground symbol
Ground (GND) is used to represent voltage reference (0 V), arbitrarily.

23. current sources
current source

24. resistors

25. capacitors

26. i-v relation of a capacitor

27. inductors

28. i-v relation of an inductor

29. Passive sign convention
A circuit element absorbs power when the current flows into the positive terminal.
For passive devices, the terminal into which current comes becomes a positive terminal.
For independent sources, current flows out of the positive terminal.

30. Example
Power is generated
Power is absorbed

31. Example : passive sign convention
Power = 0.1 * 1.5 = 0.15W (absorption)
Power = -0.1 * 1.5 = -0.15W (generation)

32. Power
Power is defined to be the energy dissipated per unit time.

33. Tellegen’s theorem
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.
54W
-18W
-36W
-36W + 54W -18W = 0

34. Example 1.2
Given the two diagrams shown in Fig. 1.12, determine whether the element is absorbing or supplying power and how much.
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 is
supplying power.

35. Example 1.3
We wish to determine the unknown voltage or current in Fig
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.

36. Example E1.4
Determine the power supplied by the dependent sources in Fig. E1.4.
(a) Power supplied = 80 W;
(b) power supplied = 160 W.

37. Example 1.7
Use Tellegen’s theorem to find the current Io in the network in Fig
Io = 0
Io = 1A

38. Example 1.8
The charge that enters the BOX is shown in Fig Calculate and sketch the current flowing into and the power absorbed by the BOX between 0 and 10 milliseconds.