Impedance of Passive Components |
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Impedance of Passive Components
[1] Ideal Electrical Elements (Capacitance &Inductance)
[2] Real Passive Components (Capacitor & Inductor)
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Impedane, Introduction
[Qualitative View] Response of Capacitor & Inductor
DC - Capacitor: Conductive line is disconnected by capacitor. The only small DC current can pass, which is determined by resistance of dielectric. e.g.) C0G: IR=1011~12Ω / X5R: 108~9Ω
DC - Inductor: All conductive line is connected through coil. DC current is determined by resistance of coil. e.g.) 1608m 0.47uH PI: Rdc(DCR)=43mΩ, 0402m 1nH High F: 400mΩ
AC - Capacitor: AC current can pass easily through capacitor by electrostatic induction.
AC - Inductor: AC current is blocked by inductor. *Electromagnetic induction
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Impedane, Definition
Impedance is a general term for resistance including reactance
- Impedance: A measurement of difficulty for electric current to flow
DC (freq.=0HZ): Z = R
AC (freq. >0HZ): Z = R + jX
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Reactance, induction
[In-depth Study] C & L definition & induction of reactance formula
C ≡ Q/V
Q=CV, I=CdV/dt, I=C(jwV), Xc=V/I=1/jwC=1/j2πfC, Q: quantity of electric charge
L ≡ Φ/I = dΦ/dI
Φ=LI, dΦ/dt=LdI/dt, V=L(jwI), Xl=V/I=jwL=j2πfL, Φ: magnetic flux, Faraday's law of electromagnetic induction
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Reactance, Xc, Capacitance
Reactance of capacitance(|Xc|) decreases as frequencies increase
- Also, |Xc| decreases as capacitance increases
Xc=1/jwC=-j/2πfc → |Xc|=1/2πfc
※ In-depth study
log(|Xc|)=log(1/2πfC)=-log(f)-log(2πC)
if y=log(|Xc|) & x=log(f), y=-x-log(2πC)
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Reactance, Xc, Capacitance
[Qualitative View] Reason for decrease of Xc as freq. and C increase
As frequency increase, Low frequency, Large Q, High V, High Z, High frequency, Small Q, Low V, Low Z
As capacitance increase, Low Capacitance, Constant Q & Small C, High V, High Z, High Capacitance, Constant Q & Large C, Low V, Low Z
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Reactance, XL, Inductance
Reactance of inductance(|Xl|) increases as frequencies increase
- Also, |XL| decreases as inductance decreases
|XL| = 2πfL
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Reactance, XL, Inductance
[Qualitative View] Reason for decrease of XL as freq. and L increase
As frequency increases - Electromagnetic induction is proportional to the chaning rate of magnetic flux.
High F > High changing rate of current, > High changing rate of magnetic flux > High V > High Z
As inductance increase - Increase of coil turn leads to high induced voltage.
Large N > High L (inductance) > High electromagnetic induction > High V > High Z
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Sum of Impedance (1)
Total impedances in series and parallel are as below
Total Impedance in Series - Z > Ztotal = Z1+Z2
Total Impedance in Series - Xc > 1/Ctotal=1/C1+1/C2
Total Impedance in Series - Xl > Ltotal = L1+L2
Total Impedance in Parallel - Z > 1/Ztotal = 1/Z1+1/Z2
Total Impedance in Parallel - Xc > Ctotal = C1+C2
Total Impedance in Parallel - Xl > 1/Ltotal = 1/L1+1/L2
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Sum of Impedance (2)
Total impedance of C or L in series and parallel are as below
Total Impedance in Series - Xc > Ctotal = 1/(1/C1+1/C2)
Total Impedance in Series - Xl > Ltotal = L1+L2 = 3.2nH
Total Impedance in Parallel - Xc > Ctotal = C1+C2 = 3.2uF
Total Impedance in Parallel - Xl > Ltotal = 1/(1/L1+1/L2)
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Sum of Impedance (3)
Total impedance of C and L in series and parallel are as below
Total Impedance in Series - X > 1uF, 1nH
Total Impedance in Parallel - X > 1uF, 1nH
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Impedance of Passive Components
[1] Ideal Electrical Elements (Capacitance &Inductance)
[2] Real Passive Components (Capacitor & Inductor)
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Impedance of Real Capacitor (1)
Real capacitor has resistance and inductance as well as capacitance
- Capacitor turns into inductor above SRF (Self-Resonant Frequency)
Z=-j/2πfC + ESR + j2πf * ESL
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Impedance of Real Capacitor (2)
Real capacitor has large resistance of IR at low frequency near DC
- Large ESR can appear with wide frequency range around SRF
At very low frequency near DC / At high frequency
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Impedance of Real Capacitor (3), Web Library
Impedance graph of 0603 1uF MLCC can be found at SEMCO homepage
- SEMCO homepage : http://www.samsungsem.com/kr/index.jsp
[Structure of MLCC] Dielectric(BaTiO3), Internal electrode(Ni), External Electrode (Cu)
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Real Capacitors in Parallel
Capacitors in parallel can decrease total impedance
- Total impedance can be controlled by applying various capacitors in parallel
Same capacitors in parallel / Different capacitors in parallel
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Low ESL Capacitor (1)
Low ESL capacitor shows lower ESL above SRF than normal MLCC
- Low ESL capacitor has low impedance at high frequency
[ESL Comparison according to MLCC types]
MLCC: Multilayer Ceramic Capacitor
LICC: Low Inductance Ceramic Capacitor
SLIC: Super Low Inductance Capacitor
3T Cap.: 3 Terminal Capacitor
VLC: Vertically Laminated Capacitor
[Impedance Comparison]
Normal vs. Low ESL
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Low ESL Capacitor (2)
Mounting area can be saved by applying low ESL capacitor
(4*MLCC) → (1*3T-Capacitor) > Space Saving 36%
4*0603 1uF MLCC / 1*1005 4.3uF 3T-Cap.
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Impedance of Real Inductor (1)
Real inductor has resistance and capacitance as well as inductor
- Inductor turns into capacitor above SRF (Self-Resonant Frequency).
Parasitic element, Z=R+(j2πfL)||(-j/2πfC)
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Impedance of Real Inductor (2), Web Library
Measured impedance comparison between 2016 4.7uH and 2012 0.47uH
-CIGW201610GH4R7MLE(4.7uH) vs. CIGT201208EHR47MNE (0.47uH)
CIGW201610GH4R7MLE (2016 1.0Tmax): L=4.7uH, Rdc~240mΩ, C=5.8pF
CIGT201208EHR47MNE (2012 0.8Tmax): L=0.47uH, Rdc~35mΩ, C=3.6pF
Copyright. SAMSUNG ELECTRO-MECHANICS All rights reserved. |