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CD4008 4-Bit Full Adder IC

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The CD4008 is a high speed, high voltage 4-bit full Adder IC with carry out feature. The IC has four independent stages of full adder circuits in a single package. It is commonly used in applications where arithmetic operations are involved.  

 

Pin Description 

Pin Number

Pin Name

Description

1,3,5,7

A1, A2, A3, A4

First Input for the adder circuit (Four pin for four stages)  

15,2,4,6

B1, B2, B3, B4

Second Input for the adder circuit (Four pin for four stages)  

9

CI

Carry Input - from previous stage if present. 

10,11,12,13

S1, S2, S3, S4

Output pin for the Adder circuit (Four pin for four stages)  

14

CO

Carry Out pin to cascade with other ICs. 

 

Specifications CD4008

  • 4-bit Full Adder with Carry Out
  • Nominal Operating Voltage: 5V, 10V, 15V
  • Maximum Operating Voltage: 20V 
  • Sum-in to Sum-out time: 160nS
  • Noise Margin when operating at 5V: 1V
  • Maximum Input Low Voltage: 1.5V
  • Minimum Input High Voltage: 3.5V
  • Available in 16-pin PDIP, CDIP,SOIC, TSSOP packages

Note: The Specifications are applicable when the IC is operating at 5V. Complete Technical Details can be found at the CD4008 datasheet given at the end of this page.

 

CD4008 Equivalent

74LS83, NTE4008

 

Where to use CD4008 IC 

Although today we have cheap microcontrollers that could perform all arithmetic operations required for our application, in early days the ICs like Adder, Counter, flip-flops etc were used for same.  This way the complexity and the BOM cost of the circuit design will greatly go low. 

The CD4008 is a Full Adder with Carry in and Carry out feature. It is a four stage 4-bit counter, meaning it has four individual Full adder circuits each of 4-bit inside a single package. It can also be easily cascaded if more than four stages are required.

 

How to use a CD4008 Full Adder IC

Using the Full Adder IC is pretty much straight forward. The IC has four different stages and each stage has two normal inputs Ax and Bx with an additional carry input called C1. Based on the values provided to these pins the output Sx will either be high (logic 1) or low (logic 0). The IC also has a Carry Out (CO) pin which will go high if the result has an carry. The block diagram below represents the same.

CD4008 Block Diagram

Each Fuller adder stage will obey the truth table below. Where Ai, Bi and Ci are the input and SUM, Co are the outputs.

CD4008 Full Adder Truth Table

Let’s understand a bit more about this IC by using a simulation. The below gif file shows the IC being simulated for all four stages by clubbing in the four input pins of both A and B. This way we can verify the truth table. 

CD4008 Circuit Simulation

The complete working with full simulation video can be found in the video linked below.

Applications

  • High Speed Arithmetic operations 
  • Miniature calculators 
  • Counters 
  •  Simple logic control designs 

 

2D Model of CD4008 (PDIP)

Cd4008 IC Dimensions

Component Datasheet