Description

7485 DIP 4-Bit Magnitude Comparator

74LS85 or SN54/7485 is a 4-bit magnitude comparator of two binary format inputs. In electronic devices besides addition and subtraction comparison of binary numbers is also important to perform the operations. To solve this issue, we use TTL-based comparators. The basic function of the comparator is to compare the two input bits and then give the three outputs. The output will always be in 3-bits which will describe the input relation with each other. The input can be greater or equal to each other. By using logic gates the comparators can be designed but to avoid large circuit sizes we can use the premade comparator IC.

74LS85 4-Bit Comparator Introduction

The IC 74LS85 is a magnitude comparator integrated circuit that can be used to compare binary data. It is smaller in size and it comes in multiple packages to fulfill the requirements of different circuits. The 74LS85 can compare two 4-bit binary data and output can be received from the output pins in the form of HIGH and LOW state. IC 74LS85 receives 8 parallel inputs for two 4-bit binary data and gives the output in 3-bit in parallel form. The IC has low power consumption and it gives the output in TTL form, which makes it compatible with other TTL-based devices and microcontrollers.

Specifications:

• The voltage range for IC is 4.75 to 5.25.
• The input voltage for the HIGH state is a minimum of 2 and the LOW state is a maximum of 0.8.
• The output current for the HIGH state is -0.4mA and the LOW state is 8mA.
• IC can operate up to 0 to 70 degrees.
• IC has internal protection from clamp voltages whole range is about -1.5V.

For more electrical and mechanical dimensions check the datasheet

How 74LS85 Comparator Works? 

The make the IC workable we will need to connect the IC first with the power supply and further with a TTL device or microcontroller to use it. In other ICs like an adder, the IC starts working from LSB but in the comparator, the IC will start comparing from the MSB. The data will start comparing from MSB and it will go to the LSB. In this case, at any point, if data A is bigger than the data B or vice versa then the output will be decided. In IC the input data will be of two parts with 4-bit each and output data will be of 3 bits. In input, the data can be any binary numbers but in output data, only one bit will be HIGH other will be LOW and all three bits will describe the output on the base of input.  Here’s the circuit of IC as a 4-bit comparator.