Decoder: the Circuit and Diagram Semiconductor Configurations

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  • Published : December 21, 2012
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Contents

← Introduction
← Basic gates
← Operation of the circuit
← Working of the circuit
← Circuit diagram
← Semiconductor configurations
← Applications of decoder
← Parts list
← Bibliography

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Introduction

The decoder is the circuit which is used to decode the BCD count into its equivalent decimal readout. The IC used in this circuit to decode the BCD count into its equivalent decimal is the famous IC 7447. This IC is the member of TTL family which is available in different series of the TTL classifications. The TTL family consists of SN 7447N, SR 7447P, SP 74LS47, SN 74HS47, etc.

The circuit drives the large size digital display via current limiting resistors and the display is basically the common anode type display.
The outputs of the IC are active LOW type and therefore the negative logic is used in the circuit. Due to this the IC can count up to 16 BCD steps, but since the single display is used in the circuit hence the figures after the 10th count are meaningless.

Decoders - Decoder is a logic circuit which is the opposite of encoder. Thus if a decoder is connected to the output of encoder then we will get original signals.
Decoder is defined as a logic circuit which is used to decode the signals already encoded, i.e. it is used to read the encoded information into its equivalent convenient form. Typically a very few ICs are used as decoder logic circuit; they are IC 7445 & IC 7446. Schematic diagram of these ICs is given below -

[pic]

• IC 7445 - Typically the decoder can be readily built by directly using this IC 7445. This IC has in all 16 pins; each pin has a particular function. Pin 16 is positive and pin 8 is negative. Then the BCD inputs are connected to pin 12 to 15 and the outputs are taken from pin 1 to 7 and pin 9 to 11. It is capable of giving the BCD conversion from 0000 to 1111. It can drive the load connected across the outputs having a...
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