BE Lab Manual Experiment 10

Experiment 10 

Aim: - To study IC 74154 as 1:16 Demultiplexer and verify its truth table


Apparatus: - 1:16 Demultiplexer kit, Digital multimeter, patch chords.


Theory: - Demultiplexer means one into many. A Demultiplexer is a logic circuit with one input and many outputs. By applying a control signal, we can steer the input signal to one of the output lines. Figure (1) shows the basic idea, which has one input signal m control signal and n output signals.


1 – 16 Demultiplexer consists of one data input (D), 4 control signals (A3, A2, A1, A0) and 16 outputs (Y0 – Y15).


The data D to be transmitted towards the output line depends on the control signal. If A3, A2, A1, A0 = 0000 then data bit D0 is transmitted only to the Y0 output giving 


Y0 = D

If   D is low/high then output Y0 will be low/high respectively. If the control signal change to A3, A2, A1, A0 = 1111, then data input D is transmitted only to the Y15, output, Y15 = D

The 74154 is a 1–16 De-mux with a pin diagram as shown in figure (2). Pin 18 is for the data input D and pin 20 -23  are the control bits A3, A2, A1, A0, pins 1-11  and 13 – 17 are the output bits  Y0 – Y15 pin 19 is the strobe which enables the circuit. It is an active low signal, which enables the circuit to then grounded, otherwise output is high at all output lines.


Pins 24 are for Vcc (+5V) and pin 12 for ground figure 3 shows the truth table of IC 74154, notice the STROBE input, it has to below to activate the IC 74154. When STROBE is low, the control signal inputs A3, A2, A1, A0 determine the output lines. When data input is high all output lines are high. Similarly when the strobe is high, all output lines are high.


D:\bhupesh shukla 29-01-10\D LAB\de multiplexer.jpg

Truth table: 

Procedure:-

  1. Study the circuit diagram provided on the front panel of the kit.

  2. Connect control inputs A3, A2, A1, A0 to logic inputs.

  3. Vary the control data inputs A3, A2, A1, A0 & observe the corresponding output as per the truth table.

Conclusion:-

IC 74154, 1:16 Demultiplexer which connects only 1 input to many outputs depending on the control inputs.

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