# ELE 704EE8502 Analog CMOS Integrated Circuits Assignment1

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```							   ELE 704 / EE8502 Analog CMOS Integrated Circuits
Assignment 1

Instructor : Dr. Fei Yuan

Q1. The common-source ampliﬁer is shown in Fig.1. Assume the transistor is in saturation.
2
Derive the expressions of the input-referred noise voltage generator vn and input-referred noise
current generator i2 of the ampliﬁer at low frequencies. Derive the noise ﬁgure expression of
n

the ampliﬁer at the input at low frequencies.

RD

Input source                vo

Rs

vs

Figure 1: Common-source ampliﬁer.

Q2. The schematic of the common-source ampliﬁer with a diode load is shown in Fig.2. Derive
the expression of the voltage gain of the ampliﬁer at low frequencies.

M2
vo

v in        M1

Figure 2: Common-source ampliﬁer with diode load.

Q3. The schematic of a widely used biasing circuit is shown in Fig.3. The aspect ratio of
1
the current mirror M1-M2 is k. Neglect the eﬀect of channel length modulation. Derive the
expression of the biasing current Ib .

M4

M3                 Ib

M1          M2

Figure 3: Biasing current source.

Q4. The schematic of the common-source ampliﬁer with a current source load is shown in
Fig.4. Note that all transistors are biased in the saturation. Show that the maximum output
voltage of the ampliﬁer is given by vo,max = Vb + |Vtp |, where Vtp is the threshold voltage of
is that if we set Vb = VDD − |Vtp |, then vo,max = VDD . Since vo,min = Vsat , where Vsat is the
pinch-oﬀ voltage of nMOS transistors, the swing of the output voltage can therefore be nearly
rail-to-rail, i.e. from Vsat to VDD .

Vb       M2
vo

v in        M1

Figure 4: Common-source ampliﬁer with current source load.

2

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