CENTRAL ELECTRONICS CENTRE

IIT MADRAS
 Instruction to the Students
• There are four practical sessions at CEC for each batch.
• Each Lab session consists of instruction Session (30
minutes) followed by practical work(2 Hours)
• The topics covered during each session are given below
– Introduction to test and measuring Instruments, components and
devices
– Application of Electronic circuits
– *Practical Performance evaluation
• Every one should prepare the answer for the Assignments
given at the end of practical test and get it signed by Lab
incharge
• After all the laboratory classes are over, there will be a
written exam for one Hour Refer the notes given to you for
the examination schedule 2
• The evaluation pattern is given below

– Practical Performance evaluation 30%

– Written Quiz 30%
– Assignments 20%
– Attendance 20%

• * Each student has to solder the given circuit on a

PCB and test it in one hour during the 4th Lab
Session. Neatness and completion of the circuit will
be evaluated for practical performance

3
I B.TECH ELECTRONICS WORKSHOP
(A PART OF WS1020- 4 Credit)

LAB SESSION-1

ELECTRONIC COMPONENTS, MEASURING

INSTRUMENTS, SIMPLE CIRCUIT WIRING
PRACTICES AND MEASUREMENTS.

4
 OBJECTIVES
To learn about:

• The Use of following Measuring Instruments

- Digital Multimeter

- DC Power supply

- Function Generator

- Oscilloscope

• Wiring and Testing of Electronic Circuits

5
 EQUIPMENT AND COMPONENTS
REQUIRED
• DMM
• DC Power Supply
• Function Generator
• Oscilloscope
• Resistors
• Capacitors
• Bread board

6
 Resistors
Standard resistor: In these resistors the first and second ring are the resistive value, the third is the
multiplier, the fourth is the tolerance
Precision resistors: In these resistors the first, second and third ring are the resistive value, the fourth
is the multiplier, and the fifth is the tolerance.

7
 Capacitors
• Most capacitors have numbers printed on their bodies to indicate their
electrical characteristics. Larger capacitors like electrolytics usually
display the actual capacitance together with the unit (for example, 220 μF).

• Smaller capacitors like ceramics, however, use a shorthand consisting of

three numbers and a letter, where the numbers show the capacitance in pF
(calculated as XY x 10Z for the numbers XYZ) and the letter indicates the
tolerance (J, K or M for ±5%, ±10% and ±20% respectively).

• Example
A capacitor with the text 473K 330V on its body has a capacitance of 47 x
103 pF = 47 nF (±10%) with a working voltage of 330 V.

• Letters such as p (pico) or n (nano) are used in place of the decimal point
to identify its position.

• For example, a capacitor can be labelled as, n47 = 0.47nF, 4n7 = 4.7nF or
47n = 47nF.

8
 Temperat
ure Working
Digit Digit Multiplier Tolerance Tolerance
Colour Coefficie voltage
A B D T > 10pf T < 10pf
nt V
TC
Black 0 0 x1 ± 20% ± 2.0pF

Brown 1 1 x10 ± 1% ± 0.1pF -33x10-6

Red 2 2 x100 ± 2% ± 0.25pF -75x10-6 240v

Orange 3 3 x1000 ± 3% -150x10-6

Yellow 4 4 x10k +100%,-0% -220x10-6 400v

Green 5 5 x100k ± 5% ± 0.5pF -330x10-6 100v

Blue 6 6 x1m -470x10-6 630v

Violet 7 7 -750x10-6

Grey 8 8 x0.01 +80%,-20%

White 9 9 x0.1 ± 10%

9
 Digital Multimeter

• A multimeter is an electronic
measuring instrument that
combines several measurement
functions in one unit. A typical
multimeter may include features
such as the ability to measure
voltage, current and resistance.

• Other optional Features:

– Capacitance, Frequency and
Temperature Measurements
– Diode Checking capability 10
 Features and Specification of Typical DMM

• Basic Accuracy 0.25 %

• Resolution 3 ¾ Digit
• Auto Ranging/ Manual Mode
• DC Voltage measurement 30.00mV to 1000V
• AC Voltage measurement 3.000V to 1000V
• DC Current measurement 300.0µA to 10A
• AC current measurement 300.0mA to 10A
• Resistance measurement 30.00Ω to 30.00MΩ
• Diode and continuity test mode
• Capacitance measurement 30.00nF to 30.00µF
• Frequency measurement 300.0Hz to 100.0kHz
• Temperature measurement with Pt 100/Pt 1000

11
 DC POWER SUPPLY

OUTPUT 32V/2A ±15V/0.5A 5V/5A

Input Voltage 230V AC, ±10%, 50Hz, 1 Phase

Output Voltage 0 to 32V 12V to 15V 4.50 to 5.50V

Output Current 0 to 2A 0.5A 5A

Line Regulation CV ±0.01% ±2mV ±0.1% ±0.1%

Load Regulation CV ±0.01% ±2mV ±0.1% ±0.1%

Line Regulation CC ±0.1% ±±250μA

Load Regulation CC ±0.1% ±±250μA

Output Ripple 1mV rms 1mV rms 1mV rms

12
 DC Power Supply

• A regulated power supply provides electrical energy

which is precisely controlled. Power supplies can be of
the type Constant-Voltage or Constant-Current.

• A Constant-Voltage (CV) supply provides a DC voltage

that can be set to any desired value over a specified
range. An ideal constant -voltage supply has a zero
output impedance.

• A regulated constant voltage DC power supply provides

constant DC voltage, irrespective of load variation (up
to the maximum allowable current).

• On the other hand, a constant-current (CC) supply

gives a regulated current independent of the voltage
over the load (up to the maximum allowable voltage). 13
 A Simplified View of a Power Supply
• Look at the power supply in the constant-voltage (CV) mode. A CV
power supply can be considered to be a "near-ideal" battery with a
very low internal resistance. Figure illustrates this view of the
power supply.

• Note that the ground terminal (┴) is isolated from the output and is
connected to the chassis (or case ) ground, which is also
connected to the earth ground through the 3-wire receptacle.

• The +25V and -25V supplies' outputs have a common output

terminal (denoted by "com") which is isolated from the case or
chassis ground. The positive or negative terminals of each output
can be grounded or each output can be left floating with respect to
the ground .

14
 Types of Regulation
Load regulation

• It is found that when a load is added to the output of a power supply,

the voltage at the terminals can fall slightly. This is obviously not
desirable because the output voltage should remain exactly constant in
an ideal world.

• The power supply load variation is normally quoted in a millivolts

variation or in percentage of the maximum output voltage. It might
typically be a few millivolts (e.g. 5 mV) or 0.01% for a step load change
from 0 to 100% load. It is normally quoted for a constant line voltage
and at steady temperature.

Line regulation

• It is found that when the line or input voltage changes, then a small
variation may be seen on the output.

• The specification is normally quoted in millivolts for a given input

variation. It may also be expressed as a percentage of the output
voltage and it should typically be a few millivolts (e.g. 5 mV) or around
0.01% of the maximum output voltage for most supplies for a change of
line voltage anywhere within the operating range.
15
Function Generator

16
 Typical Specifications
• Wide Frequency Range : 0.03Hz to 3MHz
• Function Output : DC,Sine, Triangle, Square,
Ramp Pulse, TTL (Sync.)
• Low sine wave Distortion : <1%
• Square Rise/Fall Times : <75nSec.
• Time Symmetry : 15% to 85% variable
• Output Amplitude : 20Vp-p in open circuit,
10Vp-p in 50 ohms Load

17
 Important Front panel Controls

• Frequency/ Vp-p display selection switch: To select either frequency or peak to peak
amplitude mode for display.

• Frequency range selection switches: Pushing one of the push button switches at a
time select the desired frequency in decades from 0.03 Hz to 3MHz.

• Frequency Coarse and Fine control Knobs : To set the desired frequency of function
between 0.1 to 1 times the frequency range selected. User can accurately set the
desired frequency using fine control Knob.

• Function Switch: Three inter locking push button switches provide selection of the
desired output wave form.(Sine, Triangle and Square) Pressing one switch will
release the switch previously pressed. When all switches are depressed then DC
function is selected.

• DC Offset control knob: This knob with ON/OFF control is provided to allow the DC
level of the output wave forms to be set as desired upto +/- 10V.

• Symmetry control knob: Time symmetry (Time of positive and negative cycle) of the
output waveforms, as well as the TTL pulse output is controlled by this knob. So
that variation from 10% to 90% symmetry is obtained. This unique feature provides
ramp waveforms, variable duty cycle pulses and skewed sine waves.
18
OSCILLOSCOPE

19
What does an oscilloscope do?

• An oscilloscope is easily the most useful instrument

available for testing circuits because it allows you to
see the signals at different points in the circuit.

• The best way of investigating an electronic system is to

monitor signals at the input and output of each system
block, checking that each block is operating as
expected. With a little practice, you will be able to find
and correct faults quickly and accurately.

• It draws a V/t graph, a graph of voltage against time,

voltage on the vertical or Y-axis, and time on the
horizontal or X-axis.

20
 Oscilloscope front panel controls

• Many of the controls of the oscilloscope allow you to

change the vertical or horizontal scales of the V/t graph,
so that you can display a clear picture of the signal you
want to investigate. 'Dual trace' oscilloscopes display two
V/t graphs at the same time, so that simultaneous
signals from different parts of an electronic system can
be compared.

• Power ON Switch: The green LED illuminates and, after

a few moments, you should see a small bright spot, or
trace, moving fairly slowly across the screen.

• Intensity and Focus : When these are correctly set, the

spot will be reasonably bright but not glaring, and as
sharply focused as possible.
21
• TIME/DIV Control : It determines the horizontal scale of the graph
which appears on the oscilloscope screen. Ex: If 50Hz square
wave is given at the input, then its time period is 1/f = 20msec. If
time/div control is 5 msec/div, then one full cycle of the wave
appears in 4 divisions in X axis.

• VOLTS/DIV Control: Adjust the vertical scale of the V/t graph. The
vertical scales for different channels can be adjusted
independently.
• DC/AC/GND selection:
– In the DC position, the signal input is connected directly to the Y-
amplifier of the corresponding channels.
– In the AC position, a capacitor is connected into the signal pathway so
that DC voltages are blocked and only changing AC signals are
displayed.
– In the GND position, the input of the Y-amplifier is connected to 0 V.
This allows you to check the position of 0 V on the oscilloscope
screen. 22
– The DC position of these switches is correct for most signals.
• Y Pos and X Pos : Y-POS moves the whole trace
vertically up and down on the screen, while X-POS
moves the whole trace from side to side on the screen.
These control are useful because the trace can be
moved so that more of the picture appears on the
screen, or to make measurements easier using the grid
which covers the screen.

• Trigger Selection: It is used to select either a part of

input signal or external signal to get the stable display on
the screen.

• Alt / Chop:
– In Alt mode, the channels are displayed on alternate
sweeps, used to view high frequency signals.
– In chop mode, the channel signals are chopped,
switched and displayed , so that all can be viewed
simultaneously. Used to view low frequency signals.
23
 Oscilloscope probes

• Because of the high frequencies often involved, oscilloscopes do not

normally use simple wires to connect to the DUT. Instead, a specific scope
probe is used.
• Scope probes use a coaxial cable to transmit the signal from the tip of the
probe to the oscilloscope, preserving those high frequencies that are so
important to accurate oscilloscope operation.
• Picture shows BNC to banana type probe.
• A passive 10x probe is shown in fig 2. Notice the switch in the probe
handle that allows to choose between 1x or 10x attenuation.

24
Wave form Measurement using Function
Generator and Oscilloscope

• Connect the Function Generator

output to the input of the
Oscilloscope.
• Vary the settings of Function
Generator and view the
effect in Oscilloscope.

25
 PRACTICAL EXERCISE
I. Study the given Function Generator and
explain the use of each control (Function
selection, range, DC offset, Symmetry,
Attenuation)

II. Study the given Oscilloscope and explain

the Use of controls i.e. AC/DC Coupling,
Triggering, Alt/Chop, time/div control,
volt/div control, intensity and focus

26
 Oscilloscope Measurement
I. Generate sine, square and triangular wave using Function
Generator. And feed the waveform to the oscilloscope input
and make the following measurements
Input Draw the wave form w.r.t Time period Frequency Duty cycle Amplitude Remarks
zero line (rms)

Square
Vp-p (–5v to +5v)

Sine
Vp-p (–5v to +5v)

Triangle
Vp-p (–5v to +5v)

Pulse
Vp-p (ov to +5v)

27
 Bread boards
• The picture shows how the breadboard holes are connected:

• The top and bottom rows are linked horizontally all the way
across as shown by the red and black lines on the diagram.
Normally the power supply is connected to these rows.

• The other holes are linked vertically in blocks of 5 with no link

across the centre as shown by the blue lines.

28
 Breadboard wiring with solderless approach
• A breadboard is used to make up temporary circuits for testing or
to try out an idea. No soldering is required so it is easy to change
connections and replace components. Parts will not be damaged
so that they will be available for re-use again and again.

• Connections on Breadboard

• Breadboards have many tiny sockets (called 'holes') arranged on

a 0.1" grid. The leads of most components can be pushed straight
into the holes.

• Wire links can be made with single-core plastic-coated wire of

0.6mm diameter (the standard size).

• Stranded wire is not suitable because it will crumple when pushed

into a hole and it may damage the board if strands break off.

29
• Fig shows series connection of resistors in bread
board.

30
• Fig shows parallel connection of resistors in
bread board.

31
 Rectifier
• A Rectifier converts AC to DC. Usually a capacitor
filters out the ripple voltage. Rectifier is often followed
by a voltage regulator.
• Half wave Rectifier:

• Full wave Rectifier:

32
 A Simple DC Power Supply

IN4001 7805
V2 1 3
+5V
9V + 2
1000uF 10uF
230V
V1
50Hz

9V

7905
2 3 -5V
1
1000uF 10uF
+

V1 V2 +5V O/P +5V O/P -5V O -5V O/P

Voltage Current Voltage Current
No Load

RL1= 470

Measure the current with DMM and Clamp meter and

compare the results
33
Cable Tester
+5V

2.2 k

Speaker

2N2219

10 F/ 25V 10k

34
 555 Timer

Features
• High-Current Drive Capability: 200 mA
• Adjustable Duty Cycle
• Temperature Stability of 0.005%/°C The maximum value of R1 + R2 for 15 V
• Timing from μs to Hours operation is 20 MΩ, and for 5 V
operation is 6.7 MΩ. 35
 555 TIMER Applications
• Precision Timing
• Pulse Generation
• Sequential Timing
• Time Delay Generation
• Pulse Width Modulation
• Pulse Position Modulation
• Linear Ramp Generator

36
 Timer
+5V

100k
IN4001
8 4
R
330
10k
10k IC 555 2N2219
1k
7 3
6

2 1 5
5
C 100 F 0.01 F

T = 1.1 R C
37
 B.Tech

Lab Session-2
SOLDERING PRACTICES
 Soldering

• Soldering is a skill that requires both knowledge and practice.

• Soldering is a method of joining metal parts using a filler metal of low

melting point (solder) below 450 °C (800 °F).

• Purpose of soldering is
(i) Good Electrical Connections
(ii) Strong Mechanical Connections

• Soldering Iron is used to melt the solder and to make the joint of the
metal parts.

• The reverse process of soldering is called de-soldering.

40
 Good Soldering

• Good Soldering requires

Clean Surface
Flux
Recommended solder type
Recommended soldering Iron type and wattage
Recommended soldering Iron tip
Good timing

41
 Flux
• Flux only cleans oxides off the surface to be soldered.
• It does not remove dirt, soot, oils, silicon, etc.
• Don’t use acid flux for electronic works.
• Use only ROSIN flux
• Now a days flux is contained in the core of the solder
wire itself.

42
 Solders
• Solder is a metal or metallic alloy used, when
melted, to join metallic surfaces together. The most
common alloy is some combination of tin and lead.
• Certain special applications may require Silver
Solder.
• Solder can be selected considering following
Low melting temperature
Narrow or No soft region
• 60/40 is the most common for electronic soldering.
• Solder wire available in different diameters, larger
diameter required for soldering connectors, small
diameters is sufficient for PCB soldering.
Tin/Lead Melting Point
40/60 230 °C
50/50 214 °C
60/40 190 °C 43
63/37 183 °C
 Soldering Iron
• To make good connection you have to heat the
junction somewhat above the melting temperature of
solder this is the job of the soldering iron.

• Soldering iron comes in different sizes.

• It is rated in terms of wattage (5W to 100W).

• Thicker connection such as connectors requires more

heat from soldering iron so we need higher wattage
soldering iron.

• Lighter connections like IC pins requires less heat so

requires only less wattage irons.
44
Different type of soldering iron tips (bits)
Don’t rub the tip with file or
abrasives
Pencil type tips are suitable for
20W to 60 W soldering iron for
electronic works.
Very importantly – remember to
tin it at the end of the session just
after switching off, otherwise the
casing will be damaged and the
tip will go rusty and will not
solder properly in future uses.
Use properly grounded tip to
protect sensitive components like
MOSFETs and ICs.
45
 Soldering
(Different steps)
• Cleaning

• Tinning
Tinning is the Process of coating fresh solder to a cleaned
soldering iron tip. It helps to reduces oxidization and
increases the amount of heat transfer to the connection.

• Soldering.

• Wetting
Wetting is the Penetration of solder into the surface of
metal parts,Actually this is the process, that gives physical
strength and good electrical connections.

46
 Desoldering Techniques
Undoubtedly, a time will come that you may have to remove the solder from a
joint, because of replacement for a faulty component or for fixing a dry joint. This is
done by the process called „Desoldering‟

Desoldering pump
The usual way is to use a desoldering pump which works like a small
spring-loaded pump, only in reverse! (More demanding users using
CMOS devices might need a pump which is ESD safe.)
A spring-loaded plunger is released at the push of a button and the molten
solder is then drawn up into the pump. It may take one or two attempts to
clean up a joint this way, but a small desoldering pump is an invaluable
tool especially for PCB work.

Desoldering Wick
An excellent alternative to a pump is to use desoldering wick which are
packaged in small dispenser reels.
This product is a specially treated fine copper braid which draws molten
solder up into the braid where it solidifies.
The best way is to use the tip of the hot iron to press a short length of braid
down onto the joint to be de-soldered.
The iron will subsequently melt the solder, which will be drawn up into the
braid. Take extreme care to ensure that you don't allow the solder to cool
with the braid adhering to the work, or you run the risk of damaging PCB
copper tracks when you attempt to pull the braid off the joint.
47
1. Battery Level Indicator
 Comparator
V1
-
Vo

V2 +

• If V1 > V2 , Vo = -Vsat, i.e. approximately -Vcc

• If V2 > V1, Vo = +Vsat, i.e. approximately +Vcc

• Response time and slew rate are important for high

speed comparators

• Typical comparator ICs- LM311, LM339, LM393

49
 LM3914 Dot / Bar Display Driver Features
• Drives LEDs, LCDs or vacuum fluorescents
• Bar or dot display mode externally selectable
by user
• Expandable to displays of 100 steps
• Internal voltage reference from 1.2V to 12V
• Operates with single supply of less than 3V
• Output current programmable from 2 mA to 30
mA
• Input withstands ±35V without damage
• LED driver outputs are current regulated, open-
collectors
• Outputs can interface with TTL or CMOS logic
• The internal 10-step divider is floating and can
be referenced to a wide range of voltages 50
 Block diagram of LM3914

Pin Details

Block Diagram
51
 Battery Level Indicator
+15V
330

3 9 1
Vout = Vref (1 + R2 / R1)
18

LM39 17
Vref = 1.2 V
14
Battery
5 16 R2 = 10 k
Voltage
15
R1 = 1.2 k
6 14
7
13
1.2k R Vout = 1.2 (1+10 k / 1.2 k)
1 12
8

10k
11 Vout 12 volts
R
10
2
2 4

52
2. Smoke Detector
 Gas Sensor (MQ-2)
• The gas sensor module consists of a steel skeleton under which a sensing
element is housed.
• This sensing element is subjected to current through connecting leads.
• This current is known as heating current through it, the gases coming close to
the sensing element get ionized and are absorbed by the sensing element.
• This changes the resistance of the sensing element which alters the value of
the current going out of it.
Sensor Type Semiconductor
Detection Gas Combustible gas and smoke
Concentration 300-10000ppm ( Combustible gas)
Loop Voltage Vc ≤24V DC
Heater Voltage VH 5.0V±0.2V ACorDC
Load Resistance RL Adjustable
Heater Resistance RH 31Ω ± 3Ω（Room Tem.）
Heater consumption PH ≤ 900mW
Sensing Resistance Rs 2KΩ-20KΩ(in 2000ppm C3H8 )
Sensitivity S Rs(in air)/Rs(1000ppm
isobutane)≥5
Slope α ≤0.6(R5000ppm/R3000ppm CH4)
Tem. Humidity 20℃±2℃；65%±5%RH
Standard Test Circuit Vc:5.0V±0.1V；VH: 5.0V±0.1V 54
 Detection scope:

• 200ppm-5000ppm LPG
and propane
• 300ppm-5000ppm
butane
• 5000ppm-20000ppm
methane
• 300ppm-5000ppm H2
• 100ppm-2000ppm
Alcohol

The typical sensitivity characteristics of the MQ-2 for several gases

(Temp: 20℃, Humidity: 65%, O2 concentration 21%, RL= 5kΩ
Ro: sensor resistance at 1000ppm of H2 in the clean air. Rs:sensor resistance at
various concentrations of gases) 55
 Smoke Detector
+5V

3.3k
MQ-2 +

A 3 8
+ -
H H 1
LM 393

B 2
- 4
5k 2.2k

56
3. Flashing LED Globe
CD4017 Ring Counter

58
Flashing LED Globe

330Ω

59
 B.Tech

Lab Session-3
 Operational Amplifier
• An operational Amplifier is a direct coupled high-gain
amplifier usually consisting of one or more differential
amplifiers and usually followed by a level translator
and an output stage

• “Operational Amplifier,” was used in the computing

field to describe amplifiers that performed various
mathematical operations, such as addition,
subtraction, multiplication differentiation and
integration

• By the proper selection of feedback components,

operational amplifier circuits could be used to add,
61
subtract, average, integrate,and differentiate.
 Ideal Vs Practical Op-Amp
Ideal op-amp
Ideal Practical + AV in
Vin ~ Vout
Open Loop gain A 105
- Zout=0
Bandwidth BW 10-100Hz

Input Impedance Zin >1M

Output Impedance 0 10-100

Zout Practical op-amp
Output Voltage Vout Depends only on Depends slightly on +
Vd = (V+-V-) average input Vc =
Zin Zout
(V++V-)/2 Common- Vout
Differential mode
Mode signal
Vin
signal ~
CMRR 10-100dB
- AV in

62
 Inverting Amplifier
By ohms law
Vin
i
Ri

Rf Vf iR f
Ri
- Vo -V f
Vo
V ~
in
+
Vo -iR f
Vi R f
Vo -
Ri
Vo Rf
A -
Vi Ri 63
 Non-inverting Amplifier
By ohms law
Vin
i
Ri
Rf
Ri Vf iR f
-
V
o
Vo Vi Vf
+

V ~
in
Vo Vi iR f
Vi R f
Vo Vi
Ri
Vo Rf
A 1 64
Vi Ri
 Automatic light controller

• LDR- Light Dependent Resistor - high resistance at dark and low resistance at light

•Comparator output high at night, the LED glows

•Comparator output low at day, the LED does not glow

 Object Detector
+5V

R1 56Ω
A VR1
IR Emitter 20KΩ +5V
+5V
K
+5V +5V +

2 _ 8
Object R2
C TP1 1 Buzzer
10KΩ
E + 4
3 U1
C
IR Detector LM393
BC109
B U
Q1 E

•IR Sensor- Emitter emits the IR light, which gets reflected by

the object , detector detects it, and its current output
proportional to strength of the IR signal.

•Detection distance can be set through the comparator input

set voltage
66
•Buzzer alarms when the object crosses the distance
 Waveform Generator
0.01µF
+12V
C1
2 _ 4 TP1
1 22KΩ 6
LM324 _
3 + R3 LM324 7 TP2
11 5 + O/P
U1 R1 47KΩ
-12V
33KΩ 9 _
TP3
R2 +12V LM324
10 + 8
PWM
VR1
20KΩ
-12V

• Square, Triangle and PWM waveforms are generated at TP1,

TP2 and TP3 respectively.

•Opamp-A compares triangle wave with 0V and generates square

wave, B- acts as integrator thus converts square wave in to
triangle wave, C- Compares DC voltage with triangle wave and 67
generates PWM-Pulse Width Modulated wave.
Typical IC – ICL 7107

Features:
• Guaranteed Zero Reading for 0V Input on
All Scales
• True Polarity at Zero for Precise Null
Detection
• 1 pA Typical Input Current
• True Differential Input and Reference,
Direct Display Drive
• Low Noise
• On Chip Clock and Reference
• Low Power Dissipation
• No Additional Active Circuits Required
• Enhanced Display Stability

68
Digital Panel Meter (DPM)

69
Digital Voltmeter using DPM
+12V
100mV 3
+ 7
6
741
2
- 4
-12V
1k 9 k Digital
Panel
1V Meter

10V 9k

1k

70
Digital Thermometer using DPM

+5V

Digital
Panel
LM35
Meter

71