電路學¶
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共同網頁¶
http://cc.ee.ntu.edu.tw/~ntueecircuit/
Bode Plot¶
x axis : \(\omega\)
代 \(\omega\) 值算出 magnitude
y axis : \(dB = 20\times log_{10}(magnitude)\)
Ch5¶
Superposition¶
step 1
make independent current source 斷路 (i=0)
step 2
make independent voltage source 短路 (v=0)
Thevenin & Norton¶
打開 terminal → 算 \(V_{OC}\) → 算 \(R_{TH}\)
==算 \(R_{TH}\) or 時 independent voltage source 短路 independent current source 斷路==
if have only dependent souces : 在 terminal 自由接上一個 voltage/current source
if have both independent & dependent sources : 打開 terminal → 算 \(V_{OC}\) → terminal 接上電線算 \(I_{SC}\) → \(R_{TH}=\frac{V_{OC}}{I_{SC}}\)
source exchange¶
Ch6¶
Capacitance¶
\(Q=CV \\i=C\frac{dV_C}{dt}\)
Inductance¶
\(\phi=Li \\V_L=L\frac{di_L}{dt}\)
Ch7¶
first order¶
step 1
\(v(t) = K_1 + K_2e^{-\frac{t}{\tau}}\)
\(i(t) = K_1 + K_2e^{-\frac{t}{\tau}}\)
step 2
in t = 0
電容形同斷路
電感形同短路
step 3
in t = 0+
電容形同 independent voltage source
\(v_C(0+)=v_C(0-)\)
電感形同 independent current source
\(i_L(0+)=i_L(0-)\)
step 4
in t=\(\infty\) (>5\(\tau\))
電容形同斷路
電感形同短路
step 5
\(R_{TH}\) 為以電容/電感為 terminal 的等效電阻
\(\tau=R_{TH}C\)
\(\tau=\dfrac{L}{R_{TH}}\)
second order¶
\(s^2Ke^{st}+2\zeta \omega_0sKe^{st}+{\omega_0}^2Ke^{st}\)
\(s^2+2\zeta \omega_0s+{\omega_0}^2=0\)
V(t)'s characteristic : \(s^2+\frac{1}{RC}s+\frac{1}{LC}=0\)
i(t)'s characteristic : \(s^2+\frac{L}{R}s+\frac{1}{LC}=0\)
(這兩個可直接從題目帶 KVL KCL 推得)
overdamped : 相異實根 \(x(t)=K_1e^{s_1t}+K_2e^{s_2t}\)
underdamped : 虛根 \(s=\alpha\pm\beta i\) \(x(t)=e^{\alpha t}(K_1cos(\beta t)+K_2sin(\beta t))\)
critically damped : 重根 \(x(t)=K_1e^{st}+K_2te^{st}\)
Ch8¶
==注意正負號!!!==
x+jy 公式¶
if \(x+jy=re^{j\theta}\) $$ \left{ \begin{array}{lr} r=\sqrt{x^2+y^2} \ \theta=\tan^{-1}{\dfrac{y}{x}}\ x=rcos\theta ,y=rsin\theta\ \dfrac{1}{e^{j\theta}}=e^{-j\theta} \end{array} \right. $$
Phasor¶
\(Xcos(\omega t+\theta)=X\angle \theta\)
\(\frac{V_M\angle \theta_V}{I_M\angle \theta_i}=Z\angle \theta_Z=R+jX\)
→ \(Z=\sqrt{R^2+X^2},\theta_Z=tan^{-1}\frac{X}{R}\)
reverse:
\(R=\sqrt{Z}cos(\theta_Z)\)
\(X=\sqrt{Z}sin(\theta_Z)\)
so \(\(j=1\angle 90^{\circ}\\ -j=1\angle -90^{\circ}\\ 1=1\angle 0^{\circ}\)\)
Z&Y¶
$$ \left{ \begin{array}{lr} Z_R=R \ Z_L=j\omega L \ Z_C=\frac{j}{\omega C}=\frac{1}{j\omega C} \ \end{array} \right. $$
\(Y=\dfrac{1}{Z}\)(單位: S (siemens))
並聯 → 相加
串聯 → 如同電阻並聯
Ch9¶
\(cos(\theta_i)cos(\theta_V)=\frac{1}{2}[cos(\theta_i-\theta_V)-cos(\theta_i+\theta_V)]\)
\(rms = \dfrac{max}{\sqrt{2}}\)
電器 120V 是 rms
Max average power¶
Power Factor¶
\(P = V_{rms}I_{rms}cos(\theta_V-\theta_i)\)
\(pf=\dfrac{P}{V_{rms}I_{rms}}=cos(\theta_z)\)
Complex Power¶
\(S=V_{rms}I^*_{rms}\\=V_{rms}\angle\theta_VI_{rms}\angle-\theta_i\\=V_{rms}I_{rms}\angle(\theta_V-\theta_i)\\=P+Qj\)
S單位:VA
P單位:W
Q單位:VARs
Ch12¶
==注意算 transfer function 時不一定直接是電阻相除,可能有並聯的情況==
e.g.
resonant¶
虛部為零時
RL : \(\omega_0=\dfrac{R}{L}\)
RLC : \(\omega_0=\dfrac{1}{\sqrt{LC}}\)
quality factor¶
series¶
\(|V_S|=Q|V_C|\\|V_S|=Q|V_L|\)
\(BW=\dfrac{\omega_0}{Q}=\dfrac{R}{L}\)
parallel¶
\(|I_S|=Q|I_C|\\|I_S|=Q|I_L|\)
\(BW=\dfrac{\omega+0}{Q}=\dfrac{1}{RC}\)
Bandwidth¶
\(BW=\dfrac{\omega_0}{Q}\)
series:\(BW=\dfrac{\omega_0}{Q}=\dfrac{R}{L}\) parallel:\(BW=\dfrac{\omega_0}{Q}=\dfrac{1}{RC}\)
\(\omega_{max}=\omega_0\sqrt{1-\dfrac{1}{2Q^2}}\)
parallel RLC with winding resistance¶
\(R_w\) = 電感內電阻
\(R_{par} = \dfrac{L}{CR_w}\)
Bode Plot¶
zeros : 分子 poles : 分母
一次¶
dB¶
弄成這種形式 \(\dfrac{100(j\omega+100)}{(j\omega+1)(j\omega+10)(j\omega+50)}\)
\(j\omega+x\)
- 若為分子 → 在 x 前 +0,x 後 +20dB/decade (x 為轉折頻率)
- 若為分母 → 在 x 前 -0,x 後 -20dB/decade
- 算出各區間的斜率
- 帶值算出最左邊的點的 magnitude,再用 20log(magnitude) 換成 dB
- 從那個點依各區間斜率劃出整個 bode plot
- 在 \(\dfrac{W}{2}\) 、\(W\) 、\(2W\) 算出真實的值,做修正 (W為轉折頻率)
phase¶
\(j\omega+x\)
- 若在分子,則 +45\(^{\circ}\)/decade, \(\omega = x\) 時通過 45\(^{\circ}\) ,直到 90\(^{\circ}\)
- 在分母則 -45\(^{\circ}\)/decade,直到 -90\(^{\circ}\)
- (若只有 \(j\omega\) (x=0) 則分子 → 一直 90\(^{\circ}\);分母 → 一直 -90\(^{\circ}\))
- 把漸進線疊起來
- 在 \(0.1W\)、\(\dfrac{W}{2}\) 、\(2W\) 、\(10W\) 算出真實的值,做修正
二次¶
\(\omega=\omega_0 → |H|=Q\)
\(\dfrac{50}{(j\omega)^2(j\omega+0.5)}\)
- 規則大致如一次,但 \(j\omega^2\) 變成是 \(\pm\) 40dB/decade
- 帶值算算出最左側 magnitude 之後,用 40log(magnitude) 換成 dB
phase¶
12.5 filter network¶
band pass filter¶
背背背
Ch13 Laplace Transform¶
表表(考試會給,不用背)¶
==convolution 不教== (信號與系統)
complex¶
initial & final value theoreom¶
initial value (切換開關前) 還是要用之前的方法算
Ch14¶
C 之轉換¶
L 之轉換¶
stable?¶
pole(分母的根)
- 在複數平面的左邊(i.e. 實部為負) → stable
- 在複數平面的右邊(i.e. 實部為正) → unstable