The Knowledge Adda

To study of 2-bit magnitude comparator using basic gates.

Apparatus required:-The following electronics components are required.

• AND Gate (IC-7408)
• OR Gate (IC-7432)
• NOT Gate (IC-7404)
• EX-OR Gate (IC-7486)
• IC-7485
• Digital IC Trainer KIT
• Connecting wires

Description:-

The comparison of two numbers is an operator that determines one number is greater than, less than (or) equal to the other number. A magnitude comparator is a combinational circuit that compares two numbers A and B and determines their relative magnitude. The outcome of the comparator is specified by three binary variables that indicate whether A>B, A=B (or) A

A = A₃ A₂ A₁ A₀

B = B₃ B₂ B₁ B₀

The equality of the two numbers and B is displayed in a combinational circuit designated by the symbol (A=B).

This indicates A greater than B, then inspect the relative magnitude of pairs of significant digits starting from most significant position. A is 0 and that of B is 0.

We have A

A>B = A₃B₃¹+X₃A₂B₂¹+X₃X₂A₁B₁¹+X₃X₂X₁A₀B₀¹

A3

¹B₃ + X₃A₂¹B₂ + X₃X₂A₁¹B₁ + X₃X₂X₁A₀¹B₀

The same circuit can be used to compare the relative magnitude of two BCD digits.

Where, A = B is expanded as,

A = B = (A₃ + B₃) (A₂ + B₂) (A₁ + B₁) (A₀ + B₀)

Symbol:-

Pin-diagram of IC 7485:-

Truth-table for comparator:-

Procedure to Perform:-

• Take Digital Trainer KIT including Breadboard, ICs and connecting leads (wires).
• Insert ICs on the Breadboard.
• According to pin configuration of IC perform the connections.
• Connect VCC (+5V) to pin no.14 and Connect Pin no. 7 to GND of IC.
• Apply different input and observe output at LED.
• Verify the output according truth-table.

Conclusion: - All the output verified the result of Truth Table.

Precaution in lab:- 

• All the connections should be tight and proper. 
• Handle the ICs carefully. 
• Check the connection once again before Switching on the Digital Trainer KIT. 
• Switch of the Trainer Kit after performing the Experiment.