Electrical Components and Circuits

Presentation on theme: "Electrical Components and Circuits"— Presentation transcript:

1 Electrical Components and Circuits
Electric current ; the motion of a charge through a medium. Electric units ; the unit of charge (or quantity of electricity) ; C(coulomb) → g of silver ion → silver metal로 환원시키는데 필요로 하는 전하량. 1Faraday = x 104 coulombs 1Faraday ; g의 은 석출 1g 당량의 원소나 화합물을 석출. ↳ (6.02 x 1023 charged particle에 대응하는) I = dQ/dt (Q : charge, A : ampere)

2 2A-1 Laws of Electricity 두 점 사이의 electrical potential (V) ; 공간의 한 점에서 다른 점까지 1개의 전하를 움직이는데 는 일. V ; volt → joule/conlomb (W/Q = V) = (I․R) R ; ohm → R의 단위 Ω(R = ρℓ/A) ↳ ohm's law G ; 저항의 역수(electrical conductance) Ω-1, S I ; Ampere P ; electrical power. joules/sec, W P = dw/dt = V․dQ/dt = V․I P = (I․R)․I = I2R. joule's law

3 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. Direct current ; 전하가 시간에 비례 Alternating current ; 전하가 주기적으로 변화하는 것.

4 2A-2 Direct-Current Circuits
series circuits Fig 2-1. a battery, a switch, & three resistors in series.

5 ⓐ 점 D에서 kirchhoff's law 적용
I4 - I3 = 0 or I4 = I3 at point C. I3 = I2 * 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

6 Voltage dividers ; Fig 2-3 a → series connection of resistor
↳ discrete increnents

7 Potentiometer ; continuously variable

8 Resistor in parallel at point A
2) Parallal Circuits Resistor in parallel at point A Kirchhoff's current law I1 + I2 + I3 - I = 0 I = I1 + I2 + I3

9 Kirchhoff's voltage law
I1 = V/R V - I1/R1 =0 V= I1R1 I2 = V/R V - I2/R2 =0 V = I2R2 I3 = V/R V = I3R3 I = I1 + I2 + I3에 위식 代入 V V V V I = --- = V1 = V2 = V3 = V Req R1 R2 R3 so that --- = G=1/R G = G + G + G Parallal resistances create a current divider I1 V/R /R1 G R G1 --- = = = or I1 = I--- = I--- I V/R /R G R G

10 (Ex. 2-1) a) the total resistance b) the current from the battery
c) the current present in each of the resistors d) the potential drop across each of the resistors

11 ( ) = --- R2 R R2,3 --- = = R2,3 = 13.3Ω R V b) The current ; V = I·R I = --- = = 0.67A R c) V = V1 + V2 + V3 V1 = I1R1 = I = I2 = I3 이므로 9.0 V1 = 15 x = 6.0V ( ) 13.3 V2 = V3 = V2,3 = 15 x = 9.0V 22.3 d) R1에서 I1 = I = 0.67G I2 = 9.0/20 = 0.45A I3 = 9.0/40 = 0.22A

12 2A-3 Direct Current, Voltage, and Resistance Measurements

13

14 2B Alternating current Circuits
Alternating voltage and current: 시간에 따라 방향과 크기가 변화하며 똑같은 변화가 계속 반복되는 전압 또는 전류. ; the simplest alternating waveform is sine-wave volt or current Cycle; one complete revolution Frequency(f) [HZ]; time number of cycles per second

15 Sinusoidal signals ;

16 2B-1 Sinusoidal Signals The AC: produced by rotation of a coil in a magnetic fiedd. A pure sine wave → 일정한 각속도로 회전 하는(시계방향) IP의 vector로 표시. (여기서 Ip : amplitude.) 주기 t 내에 2π radian 의 속도로 회전 할 때 W = 2π/t = 2πf Any time t에서 instantaneous value → Vpsinwt Vp ; maximum or peak voltage; the amplitude 순간 전류 : ⅰ= Ip sin wt = Ip sin 2πft 순간 전압 : v = Vp sin wt = Vp sin 2πft Out of phase by 90o Phase difference : phase angle(φ) 일반식 ; ⅰ= Ip sin(wt + φ) = Ip sin(2πft + φ) (rms current voltage) ;

17 DC, AC의 크기비교 ; 두 전류에 의한 저항에서 야기되는 Joule heat
DC = the effective value of a sinusoidal, current Report, heating effect of AC is calculated by averaging I2R losses even complete cycle

18 1 Hz 중의 평균 열손실 = 직류일 때의 ohm손실
square wave ; 파행도 파고율 1.00 sine wave ; 파행율 = 파고율 = 1.41 삼각파 ; 파행율 = 파고율 = 1.73

19 2B-2 Reactance in Electrical Circuits
Reactance - capacitance : capacitor inductance : inductor Use ; ① converting alternating current to DC or the converse ② discriminating among signals of different frequencies or separating ac & dc signals. Capacitors 구성 ; a pair of conductors separated by a thin layer of a dielectric substance

20 Position 1 Position 2

21 1) Capacitance ① a momentary current ② current ceases → to be changed ③ switch을 2로 discharge. Capacitor : 전류의 측정可 ① 과 ② 사이에서 switch 껌; 측면 전하가 저장 The quantity of electricity Q → 판 넓이, 모양, 공간, 절연체 의 유전상수에 의해 결정

22 1 Faraday ; 1 V의 전위치에 의해 양극판에 축적된 전하의 크기가 1 C일 때의 capacitance.
μF, PF V = 1/C ∫idt = 1/C∫ Ip sin wt dt = -1/wc Ip cos wt = 1/wc Im sin(wt - π/2) ∵ Vp = 1/wc Ip, V = (1/wc) I 1/wc = Xc → capacitive reactance 단위 Ω Xc = -1/wc V =│Xc│I

23 Coil에 직류 통과 → 자기작용에 의한 유기전압으로 인해 다른 전류 발생 자기장이 변화 → emf 발생
2) Inductance Coil에 직류 통과 → 자기작용에 의한 유기전압으로 인해 다른 전류 발생 자기장이 변화 → emf 발생 V = -L(di/dt) : 전류의 방향과 반대 L : inductance [Henrys] → [H] 1 Henry : 전류변화속도가 one A/1 sec 일 때 1volt의 전압 발생, μH ～ H 범위 V = L(d/dt)(Ip sin wt) = WLIp coowt = WLIp sin(wt + π/2) 전압의 위상이 전류보다 π/2 앞선다. V = wLI 여기서 wL을 inductive reactance라 한다. XL = 2πfL 직류만 통과, 교류 불통 (저주파 chohing coli) 직렬 연결 : L = L1 + L2 + L3

24 Rate of current & potential changes in an RC circuit
By Kirchhoff 의 voltage law Vi = Vc + VR Vi : const Vi = q/C + iR

25

26 Rate of Current & Potential Change across RL circuit.
RC circuit와 유사한 방법으로 처리 VR = Vi( I - e-tR/L ) VL = Vi e-tR/L L/R : time constant

27 2B-4 Response of Series RC Circuits to Sinusoidal Inputs
Response of series RC & RL circuits to sinusoidal inputs signal (Vs)

28

29 At sufficiently high frequencies & capacitance, φ become negligible & e vs are in phase.
1/wC은 저항 R에 비해 무시 可. ↳ 전류가 잘 흐름 At very low frequencies, the phase angle π/2

30 Voltage, current and phase Relationships for series RL circuit

31 Figure 2-9

32 Capacitive & Inductive Reactance ; impedance
Xc = 1/wC = 1/2πfC XL = wL = 2πfL Impedance Z ; 교류회로에서 전압과 전류의 크기의 비(직류회로의 저항에 해당) At, RC circuit Z = √R2 + Xc2 Z = √R2 + XL2 Ip = Vp/Z 저항과 차이점 : ① frequency dependent ② current와 voltage 사이에 phafe diffrence

33 Figure 2-10

34 <Vector diagrams for Reactive Circuits>
V가 ⅰ보다 90°늦다. at capacitence V가 ⅰ보다 90°빠르다. at inductance Z = √R2 + (XL - Xc)2 Z = √R2 + Xc2 , φ = -anctan Xc/R Z = √R2 + XL2 , φ = -arctan XL/R Z = √R2 + (XL + Xc)2 φ = -arctan (XL + Xc) / R (XL > Xc 인 경우) ex) ① peak current ② voltage drop Z = √(50)2 + ( )2 = 53.8Ω Ip = 10 v/53.8 = 0.186A Vc = x 20 = 3.7V VR = x 50 = 9.3V VL = x 40 = 7.4V

35 2B-5 Filters Based on RC Circuits
High-pass & Low-Pass Filters RC & RL circuits → low f component를 지나는 동안 high-f signals을 낮추기 위해 filter로 사용 (low pass filter) or 역이 성립. ① RC circuit에서 high-pass filter Vo : across the resistor R

36

37 Low pass filter

38 2B-6 The Response of RC Circuits to Pulsed Inputs
<Resonant Circuits> impedance Z가 최소 즉 XL = Xc 일 때 전류 I = E/Z = E/R ↳ the condition of Resonance resonant frequency fo ; 1/2πfoC = 2πfoL ∵ fo = 1/2π√LC ex) (Vp)i = 15.0 V (peak voltage), L = 100mH, R = 20Ω, C = 1.200μF.

39

40

41 2B-7 Alternating Current, Voltage, and Impedance Measurements
Parallel Resonance Filters Xc = XL fo = 1/2π√LC Z of the parallel circuit Z = √R2 + (XLXc/Xc-XL)2 At parallel circuit at resonance → Z는 최대 → maximum voltage drop 生 → tank circuit Behavior of RC Circuits with pulsed inputs RC 회로에 pulse 加 → various form (with of pulse time const) 사이의 관계에 의존 Simple Electrical Measurements Galvanometers → DC의 전류, 저항 측정 원리 : 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. 예제 참조 ☆ measurement of current and voltage.

42 2C Semiconductors and Semiconductor Devices
- 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 장점 : low cost, low power consumption, small heat generation, long life and compactness.

43 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 의 이동방향 반대. -Doping of arsenic or antimony (Group Ⅴ) → n type of indium or gallium (Group Ⅲ) → p type Positive holes are less mobile them free electrons. Conductivity of n type >conductivity of p type.

44 2C-2 . Semiconductor Diodes
Pn junction motion → diode is a nonlinear device that has greater conductance in one direction than in another. Figure A pn junction diode (c) forward - bias (d) reverse - bias → depletion layer 생성 : conductance 10-6~10-8

45 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.

46 2C-3 Transistors : Amplifying device -Bipolar -Field effect transistor. ① Bipolar Tr. : pnp, npn tr.

47 The mechanism of amplification with a bipolar transistor.
Pnp on ∽ n layer ~ 0.02mm thickness, p>>n layer. (수백배 이상), ∴The concentration of holes in p >> that of electrons in n layer

48

49 ① P-type emitter junction 에서 hole 생성
② ①번의 hole 이 very thin n-type base 로 이동 - electron 과 결합 (base current IB유발) ③ 대부분의 hole 은 base를 통해 drift 되어 collector junction 으로 attracting ④ 여기서 power supply로부터 나온 electron 과 combined 되어 전류 흐름 (Ic) The no of current carrying holes is a fixed multiple of the number of electrons supplied by the input base current.

50 Field Effect Transistors (FET)
FET - The insulated gate field effect transistor. →109~1014 Ω 의 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. 위의 n.p regions 을 silicon dioxide로 insulating

51

52 (n-channel junction FET)
current enhancement in brought about by application of a positive potential to the gate. Gate 에 "t" →substrate "_" 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 저항 증가→전류감소. 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.

53 2D Power Supplies and Regulators most ps contains a voltage regulator.

54 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 ①Half wave rectifier ②Full wave rectifier ③bridge rectifier ①:②;그림 ③ 그림

55

56 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.

57 2D-2 Rectifiers and Filters
In order to minimize the current fluctuations. L section filter : S 은 직렬 C는 병렬 연결. ⇒ peak to peak ripple can be reduced.

58 2D-3 Voltage Regulators Zener diode : breakdown condition 하에서 작동. Under breakdown condition, a current change of 20 to 30 mA may result from a potential change of 0.1 V or less.

59 2E Readout Devices Basic analog oscilloscope component

60 Schematic of a CRT

61 2E-2 Recorders Schematic of self-balancing recording potentiometer