**Analog to Digital Conversion**, abbreviated as

**ADC**. An ADC is an electronic circuit which converts its

**analog**input to corresponding

**binary**value.The output depends up on the coding scheme followed in the ADC circuit. For example Analog value may convert to Gray code, excess 3 code and so on.

**Analog to Digital converter ICs** are also available to do this operation. Which reduce the circuit complexity such that a **single IC** capable of doing Analog to Digital Conversion.

The circuit below shows a **2 bit** ADC circuit using **LM324** comparator IC. A **potential** divider network and some **combinational** circuits are used for making this simple ADC.

**LM324** best suited for Analog to Digital Converters because it has **four embedded op amps**, it require Vcc (5V) and ground only. No need of -Vcc like 741 op amp.

## Components Required for ADC

- Resistors (1Kx4)
- IC LM324
- IC 7404
- IC 7432
- IC 7409

## Design steps of Analog to Digital Converter

Truth Table of ADC

K-Maps for the design of ADC

## Circuit Diagram of ADC using LM324

## Analog to Digital Converter Block Diagram

Block diagram of ADC explains the basic operation and signal flow,

- Analog signal fed to the parallel combination of
**Comparators**, it will produce encoded signal corresponding to input analog signal.

- The encoded signal is then applied to
**Digital Code Converter**(a combinational circuit), that will produce binary output.

## Working of ADC Circuit

- This is a
**simultaneous ADC**, Simultaneous ADC is also called**flash ADC**and the**speed**of conversion is**very fast**.

- Comparators continuously compare
**reference**voltage at**inverting**terminal and**analog**voltage at**non inverting**terminal.

- The reference voltage of each comparator is derived from potential divider network.

*Reference voltage of lower comparator : Vcc (1/4) = Vcc/4*

*Reference voltage of*

**middle**comparator : Vcc (2/4) = Vcc/2*Reference voltage of*

**upper**comparator : Vcc (3/4)- If the
**analog**input**exceeds**the**reference**voltage to any comparator, that comparator turns**ON**.

- If
**all**the comparators are**OFF**, the analog input signal will be between**0**and**+Vcc/4**.

- When
**lower**comparator**ON**and o**thers**are**OFF**, then input must be between**Vcc/4**and**Vcc/2**.

- For input voltage between
**+Vcc/2**and**Vcc(3/4)**,**Lover**and**middle**comparators are**ON**.

- Above
**Vcc (3/4)**,**all**the three comparators will**ON**.

- Thus the
**input analog**voltage get converted in to encoded form with**3 output bits**, but actually we need binary output like 00, 01, 10, and 11.

- To represent 4 states in binary,
**only 2 bits**are needed, so we are using a digital combinational code converter circuit with**3 logic gates**. Thus it is possible to get**binary outputs**like 00, 01, 10, and 11.

## What is the Resolution of ADC?

- The term
**Resolution**is used to describe the**accuracy of ADC**, resolution means the number of distinct values that ADC can generate over the range of analog values.

- The output values are always in binary form, hence the resolution is typically expressed in bits. Consequently these outputs are the power of 2.

- For example, an ADC with a resolution of 4 bits can encode an analog input to 16 different levels, since
**2**.^{4}= 16

- In
**our circuit**we have 2 number of output bits, so the resolution is**2**.^{2}=4

- However the complexity of the useful circuit increases as resolution is increased.

## Components Pin out

*DAC circuit*.