The document outlines the functions and specifications of Digital-to-Analog Converters (DACs) and instrumentation amplifiers. It covers key characteristics such as accuracy, resolution, linearity, and settling time for DACs, along with common applications and requirements of instrumentation amplifiers. Additionally, it discusses the importance of considering these specifications when selecting DACs to ensure optimal performance in various applications.

2. • The data converters converts one form of data into
another form.
• A D/A converter (DAC) converts digital data into its
equivalent analog data.

3.  The output of DAC may be voltage or current.
General functional diagram of DAC includes
following blocks:
1. Digital switch control – To convert standard
logic levels (TTL, CMOS) to an analog switch
drive level.
2. Reference amplifier – To properly relate the bit
weight of analog switches to an output
amplifier which changes the output current of
the converter into voltage.

4.  DAC specifications can be classified into three
major categories:
1. Static accuracy
2. Temperature characteristics
3. Dynamic characteristics
All above categories of specifications must be
considered while selecting DAC.
Failure to consider any one of these
specifications may result in poor performance in a
given application.

5.  Resolution
 Linearity
 Settling time
 D/A Speed
 Reference Voltage
 Error

6.  This is the smallest possible change in output
voltage as a fraction or percentage of the full-
scale output range.
 For better resolution, the number of input bits of
DAC should be maximum.
 For resistor divider DAC
Resolution =
 For ladder type DAC
Resolution =

7. Poor Resolution(1 bit)
Vout
Desired Analog
signal
Approximate
output
2
Volt.
Levels
Digital
Input
0 0
1
Better Resolution(3 bit)
Digital Input
Vout
Desired Analog
signal
Approximate
output
8
Volt.
Levels
000
001
010
011
100
101
110
111
110
101
100
011
010
001
000

8.  A specified voltage used to determine how
each digital input will be assigned to each
voltage division.

9. Non-multiplier
Internal, fixed, and defined by manufacturer
Multiplier
External, variable and user defined

10. In a D/A converter, equal increments in the
numerical significance of the digital input
should result in equal increments in the
analog output voltage.
Linearity error is a measure of the
converter’s transfer curve deviation from
the ideal true straight line.

11. Digital Input
Perfect Agreement
Desired/Approximate Output
Analog
Output
Voltage
Linearity(Ideal Case)
Analog
Output
Voltage
Digital Input
Desired Output
Miss-alignment
Approximate
output
NON-Linearity(Real World)

12.  It is the time required for the analog output to settle
within (1/2) LSB of the final value after a change in the
digital input.
 Determines overall speed of the digital to analog conversion.
 Limits frequency of output signal.
Analog Output Voltage
Expected
Voltage
+VLSB
-VLSB
Settling time Time

13. The speed of D/A converter is defined as the
amount of time required to settle to a
particular accuracy.

14.  Non-Linearity
 Differential
 Integral
 Gain
 Offset
 Non-Monotonicity

15.  Difference in voltage step size from the previous
DAC output (Ideally All DLN’s = 1 VLSB)
Digital Input
Ideal Output
Analog
Output
Voltage
VLSB
2VLSB
Diff. Non-Linearity = 2VLSB

16.  Deviation of the actual DAC output from the ideal
(Ideally all INL’s = 0)
Digital Input
Ideal Output
1VLSB Int. Non-Linearity = 1VLSB
Analog
Output
Voltage

17.  Difference in slope of the ideal curve and the
actual DAC output
High Gain Error: Actual
slope greater than ideal
Low Gain Error: Actual
slope less than ideal
Digital Input
Desired/Ideal Output
Analog
Output
Voltage
Low Gain
High Gain

18.  A constant voltage difference between the ideal
DAC output and the actual.
Digital Input
Desired/Ideal Output
Output Voltage

19.  A decrease in output voltage with an increase in
the digital input
Analog
Output
Voltage
Digital Input
Desired Output
Monotonic
Non-
Monotonic

20.  Absolute accuracy of a DAC is the
difference between the analog output that
is expected when a digital code is applied
and output that is actually measured with
that code applied to the converter.
 Absolute accuracy error is caused by gain
error, zero error, linearity error or
combination of three.

21.  Zero temperature coefficient
A zero shift due to temperature
affects all output readings equally and is
expressed as µV/o
C or ppm/o
C of full scale.
The zero stability of a DAC is almost
entirely governed by the output amplifier’s zero
stability.
Since output amplifiers are usually
employed as current to voltage converters,
they operate at low closed loop gain and are
not greatly affected by changing gain.

22.  Generic Use
 Circuit Components
 Digital Audio
 Function Generators / Oscilloscopes
 Motor Controllers

23. 0 bit
nth
bit
n bit DAC
011010010101010100101
101010101011111100101
000010101010111110011
010101010101010101010
111010101011110011000
100101010101010001111
Digital
Input
Filte
r
Piece-wise
Continuous
Output
Analog
Continuous
Output
 Used when a continuous analog signal is required.
 Signal from DAC can be smoothed by a Low pass filter

24.  Voltage controlled Amplifier
Digital input, External Reference Voltage as control
 Digitally operated attenuator
External Reference Voltage as input, digital control
 Programmable Filters
Digitally controlled cutoff frequencies

25. 1. CD Players
2. MP3 Players
3. Digital Telephone/Answering Machines
1 2
3

26. Digital Oscilloscopes
◦ Digital Input
◦ Analog Output
Signal Generators
– Sine wave generation
– Square wave generation
– Triangle wave generation
– Random noise generation
1
2

27.  Cruise Control
 Valve Control
 Motor Control
1 2
3

28.  An instrumentation amplifier is a very high differential voltage gain
device.
 It is useful when detection of signal is difficult i.e. signal strength is
very small.
 Transducers like piezoelectric, thermo couple, photo voltaic cell etc.
generate very small output when subjected to a physical quantities.
 To amplify such a weak signal, instrumentation amplifiers are used.
 An instrumentation (or instrumentational) amplifier is a type of
differential amplifier that has been outfitted with input buffers, which
eliminate the need for input impedance matching and thus make the
amplifier particularly suitable for use in measurement and test
equipment.
 Instrumentation amplifiers are used where great accuracy and stability
of the circuit both short- and long-term are required.

30. Assumptions:
 Neglect Rdi, Rcm, and PSRR,
 Resistors RP1, RP2 (source resistors of V1in and
V2in) exist in the two input lines,
 Ip1, Ip2 are the two input currents and assumed
equal to Ip
 CMRR1 ≠ CMRR2; Vios1≠Vios2; Ibn1 ≠Ibn2, RF1 =
RF2; G1 = G2 = G.
 Inputs V1 and V2 are the common mode voltages
(Vcm) on amplifiers G1 and G2 in Figure and
 G3 is an ideal unity gain amplifier.

32.  Characteristics of IA:
1. very low DC offset,
2.low drift,
3. low noise,
4. very high open loop gain,
5.very high CMRR,
6.very high input impedance,
7.High slew rate,
8.Low power dissipation,
9.Differential input capability,
10.High stability with low temperature coefficient, and
11.Drift parameters are very low.
 Typical values of parameters:
1. CMRR=130dB
2. Input impedance = 1000M ohm
3. voltage gain = 1000

33.  Requirements of an IA:
1. Very high gain:
I.A. should offer finite, accurate, and stable
closed loop gain.
2. High CMRR:
The ideal circuit has infinite CMRR but it is
not possible.
3. High input impedance:
Ideally the input impedance is infinite but
practically it is about 1000M ohm.
4. Low thermal drifts:
The parameters of I.A. should not drift with
temperature or time.
5. High slew rate:
The slew rate of I.A. should be very high. It is
infinite.

34.  Applications:
1. Temperature controller
2. Light sensitivity meter
3. Flow and thermal conductivity measurement
4. Analog weight scale
5. Data acquisition systems
6. As bridge amplifier for resistance transducers

35.  The AD522 is a precision IC instrumentation
amplifier designed for data acquisition
applications requiring high accuracy under
worst-case operating conditions.
 An outstanding combination of high linearity,
high common mode rejection, low voltage drift,
and low noise makes the AD522 suitable for
use in many 12-bit data acquisition systems.
 The AD 522 was designed to provide highly
accurate signal conditioning under severe
conditions.

36. Applications:
1.As bridge amplifier for resistance transducers such as strain gauge and
thermistors.
2.In process control
3.Instrumentation systems
4.Data acquisition systems
5.Medical equipments