This document discusses digital to analog conversion. It describes how a digital to analog converter takes digital input and converts it to analog output. It explains the basic types of converters like resistor ladder converters. It also covers key performance characteristics like resolution, linearity, accuracy, settling time and temperature sensitivity.

1. DIGITAL TO ANALOG
CONVERSION
Submitted By
Kaavya. B

2. OUTLINE
Digital to Analog conversion
Types of D/A converters
D/A performance characteristics

3. TERMINOLOGY
 ANALOG: Continuously valued signal such as
temperature, speed etc… with
infinite values in between.
 DIGITAL: Discretely valued signals.
 TRANSDUCER: Device that converts one form of
signal to another.
 NODE: Processing point in a network of computers.

4. DIGITAL TO ANALOG
CONVERTER
WHAT IS DIGITAL TO ANALOG
CONVERTER?

5. TYPES OF D/A
CONVERTER
Binary Weighted Resistor
R-2R Ladder
Multiplier ladder
Non multiplier ladder
Characteristics:
Comprised of switches,op-amp,resistors.
Provides resistance inversely proportional to
significance of a bit.

6. RESISTIVE DIVIDER
4 bit D/A converter will take four digital input
and produces an analog voltage which is
proportional to the digital input.
For eg: Analog voltage in the range 0V to 1.5V.
( each step by 0.1V)

7. CONSTRUCTION
 Four resistors whose values are taken inversely
proportional to the binary weights.
 Let the inputs be D3,D2,D1and D0. (MSB D3 and LSB D0)
 Binary weights are 2³,2²,2¹and 2º.
 If RL is the load resistance. (RL>>>R)
INPUTS VOLTAGE RESISTOR
D0 V0 R
D1 V1 R/2
D2 V2 R/4
D3 V3 R/8

8. MILLMAN’S THEOREM
“ The voltage appearing at any node in a
resistor network is equal to the sum of
currents entering that node (assuming the
node is at zero potential) divided by the sum
of the conductances connected at the node”.
Voltage at = Sum of currents /Sum of
node P conductances

9. Vout = 2ⁿ-¹Vn-1 + 2ⁿ-²Vn-2
+………..2²V2 + 2¹V1 + 2ºV0 / 2ⁿ_1
FULL SCALE VOLTAGE – The output
voltage obtained when all the input bits
are in ‘1’ state.

10. D/A PERFORMANCE
CHARACTERISTICS
 RESOLUTION: The change in output voltage for achange
only in the LSB or the change in output
voltage when the count changes by one.
resolution = Full scale voltage/ Number of steps

11. LINEARITY
 Change in digital input = Change in analog output
 The linearity of a D/A converter is a measure of the precision
with which the linear input-output relationship is satisfied.
 The linearity error for a digital input is the difference between
the voltage corresponding to the dot and the voltage obtained
from the straight line. This is indicated by є.
 The normal analog output voltage change corresponding to a
digital input change equivalent to the LSB bit is indicated by ∆.
 |є|< ½ ∆ .

12. ACCURACY
Difference between the actual output
voltage to the theoretical output voltage.
It depends upon the accuracy of resistors
and the precision of the reference voltage
used.

13. SETTLING TIME
The time required for the analog output
to settle to within ±½LSB of the final
value after a change in the digital input is
usually specified by the manufacturers
and is referred to as settling time.

14. TEMPERATURE
SENSITIVITY
The analog output voltage for any fixed digital
input varies with temperature.
This is due to the temperature sensitivities of
the reference voltage source, resistors, OP
AMP, etc.
It is specified as ±ppm/°C.