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R-2R Ladder

This document describes a digital-to-analog converter (DAC) that uses an R-2R ladder network. It provides the following information: 1) The DAC uses an R-2R ladder network with a reference voltage of 5V and resistor values of R = R/2 = 10kΩ. 2) The input number is represented by variables S3, S2, S1, S0 with S3 as the most significant bit and S0 as the least significant bit. 3) The output voltage is calculated by replacing the R-2R network with its Thevenin equivalent circuit and solving for the output voltage, which is found to be -0.

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188 views4 pages

R-2R Ladder

This document describes a digital-to-analog converter (DAC) that uses an R-2R ladder network. It provides the following information: 1) The DAC uses an R-2R ladder network with a reference voltage of 5V and resistor values of R = R/2 = 10kΩ. 2) The input number is represented by variables S3, S2, S1, S0 with S3 as the most significant bit and S0 as the least significant bit. 3) The output voltage is calculated by replacing the R-2R network with its Thevenin equivalent circuit and solving for the output voltage, which is found to be -0.

Uploaded by

carrotcucumber20
Copyright
© © All Rights Reserved
We take content rights seriously. If you suspect this is your content, claim it here.
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Download as PDF, TXT or read online on Scribd
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(EC.dac.1.

sqproj)
DAC with R-2R ladder network
R

R R R

2R 2R
2R 2R 2R

S,V VR S,VR S,VR


network.
Figure 1: DAC using R-2R ladder

circuit shown in Fig. 1, R= R = 10k, and Vr= 5 V. The digital


Question: In the DAC
the
the variables S3. S2. S1, S). with Ss as the MSB and S as

nput number is represented by


Find V, if S1 is 1 and S3. S2.
LSB. The voltage at node Ak is Vr if Sk =1 and 0 Votherwise.
So are all10.
Solution:
network with its Thevenin equivalent circuit, as showi
To obtain Vo, we will replace the R-2R
is shown in
of the Thevenin resistance and Thevenin voltage
in Fig. 2. The computation
theoren has been made to
where repeated use of Thevenin's
Figs. 3 and 4, respectively,
simplify the circuit systematically.

R R R

2R 2R 2R 2 2R 2 2R RTh

VTn
SoVR SVR TS,Va S,V

of R-2R ladder with Thevenin cquivalent circuit.


Figure 2: Representation

network in the original DAC circuit of Fig. 1 with its Thevenin


Finally, we replace the R-2R
Fig. 5. This circuit is sinply an inverting
obtain the circuit shown in
equivalent circuit and
amplifier, and the output voltage given by
is

VR (1)
V VTh = =
-0.625 V.
R R R
2R
2R 2R 2R 2R

R R
RS 2R 2R 2R

ww
R
R
2R 2R

R
2R RTh R
R

for the R-2R ladder network.


Figure 3: Thevenin resistance calculation

since R and R are equal.

SequelApp Exercises: Answer the following and verify using SequelApp

numbers.
1. Find V, for the following input binary

(a) SsS2S1So= 1000.

(b) S3S2S1S%=0100.

(c) S3S2S1 S0 =0001.


numbers
superposition, find V, for the following input binary
2. Using

1001
(a) S352S,So
=

(b) S3S2SS0=1010.

will give the lollowiug outputs.


numbers (S3S2S1 So) wlhich
3. Find the input binary

(a) V.=-1.875 V.
(b) V=-1.5625 V.
2
R R R

2R 2R
2R 2R 2R

R R

2R 2R
2R 2R

R R
W-

R 2R 2R

Rg 2R
VTh -

Figure 4: Thevenin voltage calculation for the R-2R ladder network.

3
R R

R R R RTh

2R 2R 2R 2R 2R VT
S,VR SVR SVR SVR

circuit with R-2R ladder network replaced with its Thevenin equivalent
Figure 5: Original DAC
circuit.

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