Home > mini projects > 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

•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:

VI. output waveform