课程名称︰电路学 课程性质︰必修 课程教师︰陈信树 开课学院：电资学院 开课系所︰电机系 考试日期（年月日）︰2011/12/21 考试时限（分钟）：50min 是否需发放奖励金：是 （如未明确表示，则不予发放） 试题 : 1. In the circuit shown in Fig.1,a load resistor R_L is placed in parallel with the inductor L of a RL filter. (a) (10%) Determine the transfer function.Is it a low-pass filter or high-pass filter?What are its gain K and cutoff frequency ω_co ? (b) (20%) Sketch the amplitude ratio and phase shift plots fort the loaded RL filter with R=R_L=500Ω , and L=5.31mH.On the same amplitude ratio plot,sketch the amplitude ratio for the unloaded RL filter(i.e. R_L→∞).Please calculate and mark their gain K and cutoff frequency ω_co on the plot. (c) (10%) If a voltage input v_i(t)=10 cos(ω_1 t)+10 cos(ω_2 t),where ω_1 and ω_2 are 2π X 3.75 kHz and 2π X 30K kHz respectively, is given,what is the output v_o(t)? R ───■──────── + + │ │ │ ○ v_i ◆ L R_L ■ v_0 - │ │ │ - ──────────── Fig.1 2. In the circuit shown in Fig.2 ,a voltage input with a nonzero source resistance R_i is connected to a series RLC bandpass filter. (a) (10%) Determine the transfer function.What are its midband gain K and -3dB bandwidth B? (b) (20%) Sketch the amplitude ratio plot for the circuit in Fig.2 with R=R_i=143.24Ω , C=1uF and L=2.533mH. On the same plot,sketch the amplitude ratio for the circuit with R_i=0.Please calculate the ,ark their midband gain K and cutoff frequencies ω_l ω_u on the plot.What are their quality factors Q ? R_i L C ─■──▼──||── + │ │+ ○ v_i R ■ v_0 Fig.2 - │ │- ────────── 3. (30%)Draw the asymptotic Bode plot of the gain and phase for s(s+800) H(s)=───────── (s+50)(s+200) Then add the dB corrections to find the maximum value of a(ω) and the ω_t and ω_u which the gain drops 3dB below the maximum.Please mark these values on tje plot. 一百学年度第一学期Fall 2011 12/21/2011 --

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