课程名称︰电子学二
课程性质︰必修
课程教师︰吕良鸿
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）︰104/3/24
考试时限（分钟）：50分钟
试题 :
2015 电子学(二) Quiz,1 3/24
Q1:
Figure 1 shows a folded-cascode CMOS amplifier utilizing a simple current
source Q2, supplying a current 2I, and a cascoded current-source (Q4, Q5)
supplying a current I, Assume, for simplicity, that all transistors have equal
parameters g_m and r_O.
(a) Give approximate expressions for all the resistances indicated.
(b) Find the amplifier output resistance R_O.
(c) Show that the short-circuit transconductance G_m is approximately equal to
g_m1.
(d) Find the overall voltage gain v_o/v_i and evaluate its value for the case
g_m1 = 2mA/V and A_0 = 20.
http://imgur.com/tqOkOe7
Q2:
Consider the Wilson MOS mirror of Figure 2(a) for the case of all transistors
identical, with W/L = 12.5, μ_n C_OX = 400 μA/V^2, and V_A = 20 V. The mirror
is fed with I_REF = 100μA.
(a) Obtain an estimate of V_OV and V_GS at which the three transistors are
operating, by neglecting the Early effect.
(b) Noting that Q1 and Q2 are operating at different V_DS, obtain an approximate
value for the difference in their currents and hence determine I_O.
(c) To eliminate the systematic error between I_O and I_REF caused by the
different in V_DS between Q1 and Q2, a diode-connected transistor Q4 can be
added to the circuit as shown in Figure 2(c). What do you estimate I_O now
to be?
(d) What is the minimum allowable voltage at the output node of the mirror?
(e) Convince yourself that Q4 will have no effect on the output resistance of
the mirror, Find R_o.
(f) What is the change in I_O (both absolute value and percentage) that results
from ΔV_O = 1V?
http://imgur.com/ECSSb4q