Lecture9
ee101b:Common-drain amplifier(source follower)
EE101B
Department of Electrical Engineering Prof.M.Hershenson Stanford University Prof.K.V.Shenoy
km是什么意思
•Source follower with source resistance
–DC analysis
–AC analysis
–Signal range
•Source follower with current source at source –DC analysis
英语二级考试–AC analysis
–Loading effects
尖叫英文
•Source tied to bulk
Reading for this lecture •Sedra&Smith ction4.7.6
•Sedra&Smith ction6.10.1
Consider the common-drain amplifier (also called
source-follower)
V DD
V O
v i V I
•We call it common-drain amplifier becau the drain is AC grounded
•The input AC signal is fed from the gate
•The output AC signal is measured at the source •There is no need to include a resistor in the drain (in fact,even though at mid-frequencies it does not hurt performance too much,at high frequencies it is detrimental).We will e more in Lectures on
high-frequency circuit operation.
2013年江苏高考试卷There are two regions of operation
1.v I≤V t.The transistor is OFF,I D=0and the
source voltage is zero(V S=0).
2.v I≥V t and v I≤V DD+V t.The transistor is in
saturation(V D≥V G−V t).If we ignore the channel length modulation,the drain current is given by
I D=1
2
µn C ox
W
L
(v I−v O−V t)2
gourmetwhere v O is simply given byproblems
v O=I D R s
Thus the bias point is given by solving the equation,
毒贩子
v O=R S 1
2
乖戾的意思µn C ox
W
L
(v I−v O−V t)2
Note that in practice we don’t consider situations where v I≥V DD+V t becau it would mean that the input signal is higher than the supply voltage(which is extremely rare!).
curve
We can plot the large-signal transfer function v O vs.v I for R S=10kΩ,µn C ox=90µA/V2,V t=0.75,
λ=0.015,V DD
soho是什么意思
•Note that(unlike the common-source amplifier)the gain is positive.
•We willfind the value of the small-signal gain in the next pages by using the equivalent linear
small-signal model
We can plot the gain v out/v in by plotting the slope of the DC transfer curve∂v O/∂v I.
wifa
