課程名稱︰電子學(一)
課程性質︰電機系大二上必修
課程教師︰呂良鴻
開課學院：電機資訊學院
開課系所︰電機工程學系
考試日期（年月日）︰2019/12/13
考試時限（分鐘）：50 min
試題 :
1. An NMOS transistor, operating in the linear-resistance region with vds =
50 mV, is found to conduct 25 μA for vgs = 1V and 50μA for vgs = 1.5V.
(a) What is the apparent value of threshold voltage Vt = ? (7%)
(b) If kn'= 50 μA / V^2, what is the device W/L ratio? (7%)
(c) What current would you expect to flow with vgs = 2V and vds = 0.1V? (7%)
(d) If the device is operated at vgs = 2V, at what value of vds will the
drain end of the MOSFET channel just reach pinch-off? And what is the
corresponding drain current? (14%)
2. For each of the circuits shown in Fig.1, find the labeled node voltages. The
NMOS transistors have Vt = 0.9V and kn'(W/L) = 1.5 mA / V^2. (35%, 7% for
each)
+2.5V +5V
↑ ↑
∣ ┌┘
└〢 Q1
└→
｜
├─○V1
｜
┌┘
┌〢 Q2
￣ └→
∣
├─○V2
｜
〈
〉1kΩ
〈
〉
│
↓
-2.5V
+5V
↑
｜
〈
〉1kΩ
〈
〉
│
┌──┼───○V3
｜ │
│ │
｜┌─┘
└〢 Q1
─→
｜
｜
┌──┼───○V4
｜ │
│ │
｜┌─┘
└〢 Q2
─→
｜
｜
├───○V5
│
〈
〉1kΩ
〈
〉
│
｜
￣
Fig.1
3. For the NMOS amplifier in Fig.2, replace the transistor with its T equi-
valent circuit, assuming λ = 0. Derive expressions for the voltage gains
vs/vi and vd/vi. (30%)
+VDD
↑
｜
〈
〉RD
〈
〉
│
├───○ vd
│
┌┘
┌──── 〢
｜ └→
∣ ∣
(±) vi ├───○ vs
∣ ｜
∣ 〈
￣ 〉
〈 RS
〉
│
↓
-VSS
Fig.2