The document outlines a lecture on R-2R ladder network digital-to-analog converters (DAC) presented by Amarnath Katta at GMR Polytechnic. It covers the working principles, advantages, and output voltage calculations of the R-2R DAC, and provides sample problems, quizzes, and frequently asked questions along with assignment topics. Teaching aids such as PowerPoint presentations and block diagrams are employed to facilitate understanding.

1. DEPARTMENT OF TECHNICAL
DEPARTMENT OF TECHNICAL
EDUCATION ANDHRA PRADESH
EDUCATION ANDHRA PRADESH
Name : Amarnath Katta
Designation : Lecturer
Branch : Electronics and Communication
Institute : GMR Polytechnic, Paderu,Vizag Dist.
Year/Semester : III-Semester
Subject : DIGITAL ELECTRONICS
Subject code : EE505
Topic : A/D and D/A converters
Duration : 100 Mts
Sub Topic : R-2R ladder Network DAC
Teaching Aids : PPT, Block Diagrams, Model graphs
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2. EE505.69 TO 70 2
OBJECTIVES
On completion of this period ,you would be able to
know about
• R - 2R Ladder Network DAC
a) Working
b) Advantages

3. Recap
• Weighted resistors method of DAC require wide
range of resistor values.
• The tolerance of resistors must be less than %
resolution

4. R-2R LADDER NETWORK
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MSB
LSB
FIG(1)

5. 3-Bit
3-Bit R-2R Ladder Network
R-2R Ladder Network DAC
DAC
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A
B
C
FIG(2)

6. RESISTOR NETWORK
RESISTOR NETWORK
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D0 D1 D2
FIG(4)

7. Thevenin’s equivalent at XX’ ,YY’,ZZ’
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FIG(3)
The circuit is
simplified
using
Thevenin’s
theorem.

8. WORKING
• The digital input is applied to LSB i.e. 001 and node voltage
is obtained by Thevenin’s theorem.
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8
R
V
• The equivalent resistance is 3R.
• So for digital input 001 the equivalent voltage is

9. WORKING
• Similarly for digital input 010 and 100 the voltages
are and respectively.
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9
4
R
V
2
R
V
• The equivalent resistance is 3R in each case.

10. SIMPLIFIED CIRCUIT
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D0
D1
D2
FIG(13)

11. OUTPUT VOLTAGE
• The output voltage is given by
vo= ( 4D2 + 2D1 + D0 )
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R
R
V f
R
24

• The above equation shows output voltage is proportional to
the digital input.

12. • Sample problem:
Find the output voltage of a R-2R ladder
network DAC when the digital input is ‘1010’.
Sol: As the input is ‘1010’
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2
R
V

8
R
V

16
R
V

4
R
V

1 0 1 0

13. • The output voltage is,
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2
R
V

4
R
V

8
R
V

16
R
V

2
R
V

8
R
V

8
5 R
V

• V0=
• 1 x + 0 x +1 x + 0 x
•

14. ADVANTAGES
• Only two values of resistors R & 2R are required.
• It is easy to match temperature coefficients of resistors.
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15. EE505.69 TO 70 15
The following points were discussed:
• R-2R Ladder network DAC
• Working
• Advantages

16. QUIZ
• R-2R ladder network DAC is not applicable to
any n-bit digital input. (TRUE/FALSE)
(False)
• Ladder network DAC requires two resistor values
R & 2R. (TRUE/FALSE)
(True)
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17. Question asked in previous examinations
• Draw the circuit of a D/A converter using resistive
ladder and explain its operation. (Mar/April-04)
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18. Frequently asked questions
• Explain R-2R ladder network DAC. (12M)
• Find the output voltage of a 4-bit R-2R ladder
network DAC if the digital input is ‘1111’.
(6M)
• What are the advantages of a R-2R Ladder network
DAC. (4M)
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19. ASSIGNMENT
• Explain R-2R ladder network DAC.
• Find the output voltage of a 4-bit R-2R ladder network DAC
if the digital input is ‘1111’.
• What are the advantages of a R-2R Ladder network DAC.
EE505.69 TO 70 19