lvy>試卷(2022/08/12)

# 106 年 - 106 國立中山大學_碩士班招生考試_電波領域：電子學#110216

【非選題】
1.

1.(30%) Figure 1 shows a Colpitts oscillator. Assume β=100, = 0.7 V, and VT = 25 mV for BJT

Q. 【題組】

(a)(10%) Estimate the quality factor of the equivalent smnall-signal LCR circuit seen at the collector

of Q.

【非選題】
2.【題組】

(b) (10%) If the sustained oscillation occurs, what will be the oscillation frequency (in Hz)?

【非選題】
3.【題組】

(c)(10%) Calculate the small-signal transconductance gm of the transistor Q, and determine if the

feedback gain is large enough to cause oscillation. Justify your answer.

【非選題】
4.

2. (20%) Suppose we want to convert v(t)=cos(10t) to v(t) = Axsin(10t) by a phase shift circuit in Fig. 2. Determine the value of R, and what will be the output amplitude A in this case? 【非選題】
5.

3. (20%) A series RC circuit is utilized to equalize the impedance of an inductive load in Fig. 3. Determine the value of C in Fig. 3 so that the overall impedance Z becomes a pure resistance of 50 ohm in the entire frequency band. 【非選題】
6.

4. (30%) Figure 4 shows a MOSFET transistor M that makes a constant current source for a 20-kΩ load. The body terminal and source terminal of MOSFET M are tied together. Assume that = 15 V, and the transistor M has the device parameters: WIL = 80, = 50 μA/V2, =0.7 V,λ = 0.1. Suppose we want to have ID = 0.5 mA. 【題組】(a) (10%) Determine VG.

【非選題】
7.【題組】

(b) (10%) Determine the minimum allowed that still assures that M works properly as a constant current source.

【非選題】
8.【題組】

(c) (10%) Suppose the 15V supply voltage has 1% variations on it (i.e.,△ =± 0.15V). Estimate the percentage change in current Io. Note for M in saturation.

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