课程名称︰电子学(二) 课程性质︰电机工程学系大二必修 课程教师︰林宗贤 开课学院：电机资讯学院 开课系所︰电机工程学系 考试日期（年月日）︰2020/4/21 考试时限（分钟）：50分钟 试题 : 1. A CS amplifier that can be represented by the equivalent circuit of Fig.1 has Cgs = 1pF, Cgd = 0.05pF, CL = 1pF, gm = 4mA/V, and R'sig = R'L = 20kΩ (a) Find the midband gain AM. (10%) (b) Find tje input capacitance Cin using the Miller approximation. (20%) (c) Obtain the estimate of fH using open-circuit time constants. (20%) ┌─R'sig┬─Cgd───┬──┬──┐ + + │ + │ │ │ │ V'sig○ Vgs Cgs gmVgs↓ ◇ R'L CL Vo - │ - │ │ │ │ - ≡ ≡ ≡ ≡ ≡ Fig.1 Generalized high-frequency equivalent circuit for the CS amplifier 2. Consider a feedback amplifier for which the open-loop gain A(s) is given by 10000 A(s)= ──────────────── (1 + s/10000) (1 + s/100000)^2 If the feedback factor β is independent of frequency, (a) Find the frequency at which the phase shift is 180° . (25%) (b) Find the critical value of β at which oscillation will commence. (25%) -- https://imgur.com/yEoiJJx 你们或许从肉身的枷锁中解放了出来，但难道不是又进了另一个更为痛苦的牢笼吗？ 在人们造出的名为「社会」的牢笼中，被别人决定自身价值、被别人裁决的生活。我不想 为了在乐园生活而愿意沦为一名奴隶。—丁格 ———《乐园追放—Expelled from Paradise》 --

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