THE UNIVERSITY OF NEW SOUTH WALES School of Electrical Engineering and Telecommunication Assignment II
2022 ELEC2133
Analogue Electronics
This assignment contributes to 7.5% of the total assessment of this course
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The due date is on Monday July 11, 2022 (11:59pm). Assignments are to be submitted on Moodle before the due date and time. Assignments submitted after this date will attract a penalty of 5% per day.
The assignment contains one problem with four parts. Each part contains one or more questions related to the various topics covered related to transistor amplifiers. Each question has been labelled with P, C, D or HD that indicates the level of difficulty. P means that the question could be attempted by all students and students who answer the question correctly are at the level of “pass”. C means the question could be attempted by students who are at the level of “credit” in the course. D and HD indicate the question could be attempted by students who are at the level of “Distinction” and “High Distinction”, respectively.
What does this mean?
If you are targeting to pass or get credit in the course, you may only attempt those P or C types of questions.
If you are happy or targeting to get a distinction, you can attempt those P, C, and D types of questions.
If you are targeting a to get high distinction, you should attempt all the questions including HD type of questions.
Question [100 Marks]
In the assignment I, you analyzed and designed the charge readout circuit for PZT actuator shown in Fig 1(a). One of the problems that is encountered in the readout circuit is that the last stage of the amplifier, which is the non-inverting amplifier, amplifies low-frequency noise from power supply or the vibration of the actuator due to environmental factors. It also amplifies any of DC imperfections contributed from the previous stages. Reducing the noise at the output is important while ensuring the readout signal is amplified. Although there are other modifications that may be applied to the non-inverting amplifier in order to achieve high signal- to-noise ratio, the non-inverting amplifier will be replaced by a three-stage transistor amplifier shown in Fig. 2(a) in this assignment. Your task will be to analyze the amplifier by calculating its gain, input and output impedance, and bandwidth.
The three-stage amplifier consists of one n-channel MOSFET transistor M1 in depletion mode with W/L = 1 and two BJT transistors Q1 and Q2. The transistors have the model parameters as provided in the table below
PZT Actuator
Fig. 1: PZT actuator self-sensing readout circuit
M1 Kn = 10mA/V2
Transistor Parameters
VTN = -2V VA = 80V VA = 60V
λ=0.02V-1 VBE = 0.7V VBE = 0.7V
Cgs = 3.5pf, Cgd = 0.1pf fT = 2GHz, Cμ= 0.2pf
fT = 2GHz, Cμ= 0.2pf
RD2 R1 0.62K 78K
RsR22K4 Vo
10K G 120K 1M RS1
RE3 RL RE2 C4 3.3K 0.25K
C2 10μF 1.6K 10μF
Fig. 2: A three-stage transistor amplifier
PART I (Amplifiers configuration)
a) [P] Identify the amplifier configuration used in each stage of the amplifier.
b) [P,C] what are the functions of C1, C2, C3, C4, and C5 capacitors?
c) [P,C] Explain what are the purposes of each amplifier, and can a single-stage
transistor amplifier ( say stage 1 or 2 or 3) be used instead? [Hint: what are the requirements of voltage amplifiers in terms of input and output resistance? Remember the non-inverting amplifier (the last stage) in Fig. 1 is a voltage amplifier [6 marks]
PART II (Q-point and transistor model parameter calculations)
a) [P] Draw the DC equivalent circuit of the transistor amplifier in Fig, 2. Note that capacitors act as open circuit in DC conditions. [5 marks]
b) [P,C]Show that the Q-Point values are: M1( ID=5mA, VDS=10.9V), Q1 (IC=1.57mA, VCE = 5.09V), and Q2 (1.99mA, 8.36V). [12 marks]
c) [P,C] Calculate the transistor model parameters for each transistor, namely gm1, gm2, gm3, ro1, r02, ro3, rπ2 and rπ3 [16 Marks]
d) [D] *Comment on the possible range of resistance values that may replace the RC2 = 4.7K , RD2 = 0.62K of the BJT Q1 transistor in the amplifier. [Hint: BJT must operate in a forward-active region and MOSFET must operate in a saturation region
[12 Marks]
PART III (Calculating mid-band gain, input, and output resistance)
[P,C] Draw a small-signal equivalent circuit of the amplifier in the form suitable for mid-frequency. [5 Marks] [P,C,DN] *Calculate the mid-band voltage gain of the amplifier, input resistance and output resistance. [20 Marks]
[HD] **Calculate the mid-band current and power gain. [15 Marks]
[6 marks] [3 marks]
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