This document summarizes different types of digital to analog converters (DACs). It discusses the basic concept of converting digital data to analog signals by using a circuit that can produce analog outputs. It then describes several DAC specializations: 1) Binary weighted DAC which uses a reference voltage and weighted resistors to produce analog outputs corresponding to the digital input bits. 2) Flash type ADC which uses a voltage divider network and parallel comparators to directly convert an entire digital word to an analog voltage very quickly. 3) Successive approximation ADC which uses a comparator and feedback loop in a step-wise process to iteratively approximate the analog output voltage, providing a tradeoff between speed and circuit complexity.

1. UNIT-5
Mohammad Asif Iqbal
Assistant Professor,
Deptt of ECE,
JETGI, Barabanki

3. Need of conversion

4. 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.

5. DAC Specializations
Vref
So from the previous expression we may
conclude that our Vo is a function F of Vref.
Vo = F ×Vref
Consider 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…

6. Binary weighted DAC
1
0
1
0

7. At output you will begetting
that pulse as long as output
of the comparator is high.
Dual slop ADC(SLOW) Heretwopointsareworthnoting.
1. We will use the concept of
virtualground
2. No current will flow inside the
Op-Amp
Do u remember? Its a simple
comparator.
Commentaboutitsoutput…..At output you will begetting
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
havefixed count with variable
slop.
At output you will begetting
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.

8. Flash type ADC (FASTEST)
8V
7V
6V
5V
4V
3V
2V
1V
Voltage divider network
Comparator
Parity encoder
3.5V
0
0
0
1
0
1
1
0
1
1
Why/how??

9. 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
0
0 1 0 0
0 1 0 0
4
0 0 1 0
0 0 1 0
2
1
0 0 1 1
0 0 1 1
3
0
0
1
1

10. THANK YOU!