OP-AMP applications

UNIT-5

Mohammad Asif IqbalAssistant Professor, Deptt of ECE,JETGI, Barabanki

Need of conversion

Basic concept for Digital to Analog conversion

Have a look at Binary to Decimal conversion

So in order to convert digital data into analog we need a circuit which is capable of producing output similar to this.

DAC Specializations Vref

So from the previous expression we may conclude that our Vo is a function F of Vref.

Vo = F ×VrefConsider an N-bit data, So, total number of combinations = 2^N

The resolution of either a digital-to-analog converter (DAC) or an analog-to-digital converter (ADC) is the measure of how finely its output may change between discrete, binary steps.

More number of combinations mean more number of levels…

Binary weighted DAC

1

0

1

0

At output you will be getting that pulse as long as output of the comparator is high.

Dual slop ADC(SLOW) Here two points are worth noting.1. We will use the concept of

virtual ground2. No current will flow inside the

Op-Amp

Do u remember? Its a simple comparator.Comment about its output…..At output you will be getting

that pulse as long as output of the comparator is high.

Its your counter

V1

V2

t

V2>V1

t1

t2

Here you can observe , we have fixed count with variable slop.

At output you will be getting that pulse as long as output of the comparator is high.

Here the count is different but the slop is constant . Why??

Give the reason of this negative slop.

Flash type ADC (FASTEST)8V

7V

6V

5V

4V

3V

2V

1V

Voltage divider network

Comparator

Parity encoder

3.5V

000

10

11

0

11

Why/how??

Successive approximation DAC(Trade off between speed and hardware)

comparator

Its a simple DAC

SAR

3.5V

1 0 0 0

1 0 0 0

8

00 1 0 0

0 1 0 0

4

0 0 1 00 0 1 0

2

1

0 0 1 10 0 1 1

30011

THANK YOU!