VLSI代写 | VLSI DESIGN M (ENG5092)

这个作业是完成超大规模体积电路的测试
VLSI DESIGN M (ENG5092)

Q1 (a) Draw the symbols of the following transistors and indicate conduction mode at
Vgs = 0V.

(i) NMOS enhancement mode
(ii) PMOS enhancement mode
(iii) NMOS depletion mode
(iv) PMOS depletion mode
[4]
(b) What are the advantages of Dynamic Precharge Logic over Static CMOS?
[5]
(c) What are the drawbacks of a transmission gate logic and what is required to
resolve them? Illustrate you answer with a transmission gate logic diagram.
[10]
(d) Tabulate the number of transistors required for the following logic circuit.

(i) NMOS
(ii) Transmission Gate
(iii) Precharge
(iv) Clocked CMOS
(v) CMOS
(vi) Pass Gate
[6]

Continued Overleaf
Q2 (a) Sketch the transistor-level schematic circuit diagram for a CMOS cell with the
following function, using the smallest number of transistors possible.
Z =A.(BC+D) [10]
(b) Determine the stack depth size the transistors using both the linear least deep
stack and the deepest stack method, taking into account the fact that µn = 3µp
(wpi = 3 Wni) and all transistors having the same gate length. [10]
(c) Draw a 2 bit half adder using XOR and AND logic gates and produce the
logic table. [5]
Q3 (a) A pipelined system architecture must be able to arbitrarily shift data one bit to
the left, one bit to the right, or not at all, in a single clock cycle. Sketch a
circuit that will do this using pass-transistor logic. You may assume that there
is an input and an output register associated with the device. [10]
(b) Derive Elmore delay expression of the chip interconnect model shown in
Figure Q3. [7]
Figure Q3
(c) Interconnect delay imposes serious speed limitations on CMOS routing of the
clock tree. Describe a clock tree design that, if correctly implemented, will be
free of clock skew. Sketch a diagram for your design and explain why and
where it will have no skew. [8]

Continued Overleaf
SECTION B: Attempt any TWO questions [50 marks]
Q4 (a) Most digital-to-analogue converter (DAC) architectures are based on the
popular resistor-ladder (R-2R) network. Draw the circuit diagram for a 3-bit
R-2R based DAC. [5]
(b) By analysis of the circuit you have drawn in Q4(a) show mathematically how
the input bits of the DAC relate to the analogue output voltage. [5]
(c) Another popular DAC architecture, the potentiometric DAC, is based on
selecting one tap of a segmented resistor string by a switch network. State the
key advantages of this type of DAC. Briefly explain how high resolution
converters exploit these advantages. [5]
(d) An alternative DAC architecture is based on a capacitor network. Draw the
circuit diagram for a 3-bit weighted-capacitor DAC, and briefly explain its
operation. [5]
(e) What are the advantages and disadvantages of using an R-2R DAC when
compared with weighted resistor or capacitor DAC architectures? [5]