İzmir University of Economics
EEE 331 Analog Electronics
LO-1
DC and AC Small Signal Analysis of Wide Band Transistor Amplifiers
Common Source Amplifiers
1.
For the NMOS common-source amplifier given in the following figure.
(a) Determine the quiescent point values of ID and VDS.
(b) Find the AC small-signal voltage gain.
(c) Determine the maximum symmetrical swing in the output voltage.
The circuit parameters
VDD = 12 V,
RS = 2 k,
RD = 3 k,
R1 = 300 k
R2 = 200 k
RL = 3 k
The transistor parameters
VTN = 2 V,
KN = 1 mA/V2,
= 0.
2.
Repeat the Problem 1 if the source resistor is bypassed by a source capacitor CS.
3.
Consider the NMOS common-source amplifier given below.
The circuit parameters
V+ = 5 V,
V- = -5 V,
RD = 10 k,
RL = 10 k
The transistor parameters
VTN = 1 V,
KN = 0.5 mA/V2,
= 0.01 V-1
(a) Determine IDQ to achieve the maximum symmetrical swing in the output voltage.
(b) Find the AC small signal voltage gain.
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4.
For the common-amplifier given below, to minimize the loading effects, the drain resistance
should be RD 0.1 RL.
(a) Determine IQ such that the Q-point is in the center of the saturation region.
(b) Determine the open-circuit (RL = ) AC small-signal voltage gain.
(c) By what percentage does the AC small-signal voltage gain decrease when RL is
connected.
The circuit parameters
RL = 20 k
The transistor parameters
VTP = -1.5 V,
KP = 2 mA/V2,
= 0.01 V-1
5.
For the common source amplifier given below,
(a) Determine RD and RS such that IDQ = 2 mA and VDSQ = 6 V.
(b) Determine the AC small signal voltage gain.
(c) If vi = Vi sint, determine the maximum value of Vi such that vo is an undistorted sine
wave.
The circuit parameters
VDD = 10 V,
RL = 2 k
The transistor parameters
VTN = -1 V,
KN = 4 mA/V2,
= 0.
Common Drain (Source Follower) Amplifiers
6.
Consider the source follower circuit given below, if IQ = 1 mA,
(a) Calculate VDSQ.
(b) Determine the AC small signal voltage gain Av = vo/vi.
(c) Determine the output resistance Ro.
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The circuit parameters
VDD = 5 V,
VSS = -5 V,
RG = 500 k,
RL = 4 k
The transistor parameters
VTN = 1.2 V,
KN = 1 mA/V2,
= 0.01 V-1
7.
For the source follower amplifier given below,
(a) Calculate IDQ and VSDQ.
(b) Determine the AC small signal gains Av = vo/vi and Ai = io/ii.
(c) Determine the output resistance Ro.
The circuit parameters
VDD = 10 V,
RS = 4 k,
R1 = 1.24 M
R2 = 396 k
RL = 4 k
The transistor parameters
VTP = -2 V,
KP = 2 mA/V2,
= 0.02 V-1
8.
Consider the source follower amplifier given below. The circuit and transistor parameters
are listed.
(a) Design the circuit such that
IDQ = 0.25 mA and VDSQ = 1.5 V.
(b) Determine the AC small signal voltage
gain.
(c) Determine the output resistance Ro.
The circuit parameters
VDD = 3 V,
Ri = 300 k,
The transistor parameters
VTN = 0.4 V,
KN = 0.5 mA/V2
= 0
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9.
Consider the source follower with a depletion NMOS given below.
The most negative output signal voltage
occurs when the transistor is just cuts off.
Show that this output voltage vo(min) is
given by
vo (min) 
- I DQ R2
1  RS RL
Show that the corresponding input voltage
is given by
vi (min)  
I DQ
gm
1  gm ( RS // RL 
Common Gate Amplifiers
10. For the common gate amplifier given below,
(a) Calculate IDQ and VDSQ.
(b) Determine gm and ro.
(c) Find the AC small signal voltage gain Av = vo/vi.
(d) Determine the output resistance Ro.
The NMOS parameters
VTN = 1 V,
KN = 3 mA/V2,
= 0
11. For the source follower amplifier given below,
The PMOS parameters
VTP = -1 V,
KP = 0.5 mA/V2,
= 0
(a) Determine RS and RD such that IDQ = 0.75 mA and VSDQ = 6 V.
(b) Determine the input resistance Ri and the output resistance Ro.
(c) Determine the load current io and the output voltage vo, if ii = 5 sin t A.
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12. For the common gate amplifier given below,
(a) Find RD such that IQ = 5 mA and VDSQ = 12 V.
(b) Calculate gm and Ri.
(c) Determine the AC small signal voltage gain Av = vo/vi.
The circuit parameters
V+ = +10 V
V- = -10 V
RG = 100 k,
RSi = 0
RL = 2 k
The NMOS parameters
VTN = 2 V,
KN = 4 mA/V2,
= 0
Amplifiers with MOSFET Load
13. Consider the NMOS amplifier with saturated
load as given below.
(a) Design the circuit such that the AC small
signal voltage gain is |Av| = 5 and Q-point
is in the center of the stauration region.
(b) Determine IDQ and the dc value of vO.
The circuit parameters
VDD = 10 V,
The transistor parameters
VTND = VTNL = 2 V,
(W/L)L = 0.5
D= L= 0.
14. A source follower circuit with a saturated load is
shown in the figure below.
(a) Determine VGG such that the quiescent value
of vDSL is 4 V.
(b) Show that the AC small signal open circuit
(RL = ) voltage gain about this Q-point is
given
(c) Calculate the small-signal voltage gain for
RL = 4 k.
The circuit parameters
VDD = 9 V
The transistor parameters
VTND = VTNL = 1 V,
KND = 1 mA/V2, KNL = 0.1 mA/V2
D= L= 0.
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15. The ac small-signal equivalent circuit of a CMOS common source amplifier is shown below.
Determine the small-signal voltage gain
The circuit parameters
VDD = 9 V,
The NMOS transistor parameters (M1)
VTN = 0.5 V
(W/L)1 = 50
= 0.05 V-1
The PMOS transistor parameters (M2 & M3)
VTP = -0.5 V
(W/L)2,3 = 50
= 0.075 V-1
16. Consider the ac small-signal equivalent circuit of a CMOS common source amplifier given
below. Determine the small-signal voltage gain
The circuit parameters
VDD = 9 V,
The PMOS transistor parameters (M1)
VTP = -0.5 V
(W/L)2,3 = 50
= 0.075 V-1
The NMOS transistor parameters (M2 & M3)
VTN = 0.5 V
(W/L)1 = 50
= 0.05 V-1
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Multistage Amplifiers
17. Consider the multistage amplifier given below.
(a) Design the circuit such that IDQ1 = 0.2 mA and IDQ1 = 0.5 mA.
(b) Determine the resulting values of VDSQ1, and VDSQ2.
(c) Calculate the resulting voltage ac small-signal voltage gain Av = vo/vi.
(d) Determine the input resistance Ri and the output resistance Ro.
The transistor
parameters
VTN1 = VTN2 = 1 V
KN1 = 500 A/V2
KN2 = 200 A/V2
= = 0.
18. Consider the multistage amplifier given below.
(a) Determine IDQ1, IDQ2, VDSQ1, and VDSQ2.
(b) Determine gm1 and gm2.
(c) Determine the overall ac small-signal voltage gain Av = vo/vi.
The transistor
parameters
VTN1 = 1 V
VTN2 = 1 V
KN1 = 4 mA/V2
KN2 = 4 mA/V2
= = 0.
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