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4:1 MULTIPLEXER

Abstract -In electronics, an Multiplexer is a device which transmits 2^n inputs through a single channel which is contolled by n control signals.

Multiplexer is shortened as "MUX" and it is utilized in communications systems namely,Time Division Multiplexer(TDM) based transmission systems.

# I. Introduction

The multiplexer, shortened to "MUX" or "MPX", is a combinational logic circuit designed to switch one of several input lines through to a single common output line by the application of a control signal. Multiplexers operate like very fast acting multiple position rotary switches connecting or controlling multiple input lines called "channels" one at a time to the output.

The implementation of multiplexer takes three steps:

1.To get the true table of multiplexer.

2.To get the Boolean equation using the truth table by using K-Map.

3.Then, by using the above Boolean Eqaution,construct the circuit Diagram.

# II. TRUTH TABLE OF 4:1 MULTIPLEXR:

The Truth table of 4:1 mux is as follows:

 C0 C1 M 0 0 X0 0 1 X1 1 0 X2 1 1 X3

BUILDING BOOLEAN EQUATION:

By solving the above truth table using k-map we get

the output equation as:

M=c0'c1'x1+c0'c1x1+c0c1'x2+c0c1x3.

Using the above Boolean Equation the circuit diagram is drawn as:

# III. IMPLENTATION OF LOGIC GATES

The logic gates such as And,Not,Or and 3-input And gates implemented using mosfets.

AND GATE USING MOSFETS:

NOT GATE USING MOSFETS:

OR GATE USING MOSFETS:

3-INPUT NAND GATE USING AND SUBCIRCUIT:

# IV. MULTIPLEXER APPLICATIONS

Multiplexers are used for

â€¢Communication Systems.

» Telephone Networks.

» Computer memory organisation

# V.NETLIST

(i)NETLIST FOR AND SUBCIRCIRCUIT

.subckt and 1 2 5

.model mosfetnmos

.model mosfet1 pmos

m1 4 1 6 6 mosfet

m2 6 2 0 0 mosfet

m3 5 4 0 0 mosfet

m4 4 1 3 3 mosfet1

m5 4 2 3 3 mosfet1

m6 5 4 3 3 mosfet1

vdd 3 0 dc 5

.ends and

(ii)NETLSIT FOR OR SUB CIRCUIT

.subckt or 1 2 6

.model mosfetnmos

.model mosfet1 pmos

m1 5 1 0 0 mosfet

m2 5 2 0 0 mosfet

m3 6 5 0 0 mosfet

m4 4 1 3 3 mosfet1

m5 5 2 4 4 mosfet1

m6 6 5 3 3 mosfet1

vdd 3 0 dc 5

.ends or

(iii)NETLIST FOR NOT SUB CIRCUIT

.subckt not 1 2

.model mosfetnmos

.model mosfet1 pmos

m1 2 1 0 0 mosfet

m2 2 1 3 3 mosfet1

vdd 3 0 dc 5

.ends and

(iv)NETLIST FOR 3-INPUT AND GATE:

.subckt 3and 1 2 3 4

.include andmos.cir

x1 1 2 5 and

x2 3 5 4 and

.ends 3and

(v)NETLIST FOR MUX CIRCUIT:

4:1 mux

.include notmos.cir

.include andmos.cir

.include ormos.cir

.include 3and.cir

x1 1 3 not

x2 2 4 not

x3 3 4 5 9 3and

x4 3 2 6 10 3and

x5 1 4 7 11 3and

x6 1 2 8 12 3and

x7 9 10 13 or

x8 11 12 14 or

x9 13 14 15 or

v1 1 0 dc 5

v2 2 0 dc 5

v3 5 0 pulse(0 5 0 0 0 5u 10u)

v4 6 0 pulse(0 5 0 0 0 10u 20u)

v5 7 0 pulse(0 5 0 0 0 20u 50u)

v6 8 0 pulse(0 5 0 0 0 50u 100u)

.tran 0.25u .5m

.control

run

display

plot v(1)

plot v(2)

plot v(5)

plot v(6)

plot v(7)

plot v(8)

plot v(15)

.endc

.end

# V. INput waveforms

As we are giving 11 as control signals we need to check whether the input signal x3 is at the output or not.

Input signal x3 is: