Download Lab 5: Data Sheets for Discrete Components and Integrated Circuits

Technology, Engineering and Math-Science Academy for Advanced High School Students
25.151 Assistive Technology & Electronics
Lab 5: Data Sheets for Discrete Components and Integrated Circuits
Objectives:
1.
Familiarize yourself with the useful information available in component data sheets, including power ratings,
functionality, and applications
2.
Understand the “black box” nature of IC’s—if you can read a data sheet, it opens up a world of applications to an
electronics novice (we’ll use the 555 timer data sheet as an example)
Due Date/Scheduled Lab time:
Hand in on or before April 6/7
Manage your class time wisely
o One day next week is reserved for ATDF PDR
o The rest of the time from 3/23 to 4/3 is for you to use for ATDF and to complete this lab
o Much of this lab is research (looking up info on the web and gleaning information from data sheets). DON’T
DO THIS IN CLASS—DO IT AT HOME!! All of the circuit breadboarding and testing can be done at home
as well. Reserve class time for ATDF project coordination and to ask lab 5 clarification questions.
Introduction:
o
o
As you begin map out the functions of your assistive technology project, you will need to do some research to see what type of
electronics would be available to meet your functional needs. Of course, you can ask Mr. Rhine, Ms. Thomas, and Bill
Harmon for some guidance (keep in mind Bill has the best answers!!), but do some research on your own before you ask us for
guidance. In other words, search the internet! You will certainly be able to find many solutions for various portions of you
projects, but remember that you get what you pay for (or as they say in Brazil, if you pay in bananas, you’ll get monkeys).
Sometimes you can find a single integrated circuit (“chip”) that will solve part of your problem. You may also find entire
circuits designed by hobbyists that we can help you modify and test. Or perhaps you can purchase an off-the-shelf product and
cannibalize it for the parts you need. All you need to do to find and use these chips is to:
(a) be creative and think outside the box
(b) know how to “Google”
(c) be able to selectively read the data sheets to glean the important information (power requirements, application
instructions, etc.)
(d) be willing to experiment/breadboard
(e) know when to ask for a little help from someone with more experience
Manufacturer data sheets are available for not only for integrated circuits [many individual components integrated into a single
chip to accomplish a (potentially very complex) task] as well as for discrete components such as resistors, capacitors, diodes,
transistors, etc. You can look up data sheet on the internet (we have some useful ones linked to the wiki) or electronics retailer
like Jameco, DigiKey, or Mouser will have data sheets on their web sites for every part they sell. You should note that these
devices could come from many different manufacturers, each of which publishes a data sheet providing the specifications for
their version of the product. Typically the manufacturers coordinate and develop a common standard to which they all build,
but sometimes there may be minor differences in performance or different pin assignments on the package
Part I: Internet Search for Chips or Circuits that Perform a Specific Task
Use an internet search engine to find a chip that will perform the function indicated. Find chips or circuits for at least
three of the functions listed below, and post the manufacturer and chip number and link to a data sheet on your personal
wiki in an easy-to-find location for Lab 5.
Function
1
Amplify an audio signal (perhaps you need to
boost the volume of a device for a hearingimpaired person)
2
Record and play back a voice message (or
other sounds)
3
Allow you to create an electronic touch
sensor
4
Operate a 7-segment display using a binary
number input (similar to the Cricket display?)
5
Perform voice recognition
6
Convert an analog sensor input voltage into a
digital output (e.g., a binary number)
Manufacturer
Now find something useful for your AT project:
7
Write down one function your AT project
must perform and find a chip or circuit that
might be useful:
Part II: Reading Data Sheets
1. LEDs and Diodes (use the LITEON 5mm LED data sheet on wiki)
General questions…
a. What is the difference between a transparent and diffused LEDs?
We have both types in the lab—get one of each and play!
b. What is the unit price for these LEDs? Look up price for red and
green 5 mm LEDs at All Electronics or Electronics Goldmine
(assume you buy 100 at a time).
c. Define “anode” and “cathode” with respect to an LED - look up
in book or on web.
d. Name two ways to identify the cathode on an LED. Draw
diagram!
e. Does the cathode point towards the positive or negative side of
the circuit to turn the LED on? Draw a little circuit diagram
showing how to “forward bias” a LED (make it turn on).
f. What is the lead spacing of the LED in inches and mm?
g. What is the hole spacing your breadboard in inches an mm?
Part number
Unit Price
Questions for Green and Red LITEON LEDs
Green Diffused
Red Diffused
h. What is the part number?
i. What is the typical “forward voltage” (the voltage drop across the
LED when it is fully “on”)
j. What is the dominant wavelength?
k. What is the maximum forward current? (a short current “spike”
that may occur as you turn your circuit on or off)
l. What is the continuous forward current? (this is the typical
average current you would want to flow through the LED).
m. What is the maximum power dissipation?
2. Quick overview…Diodes & LEDs (want to know more? Read about PN junctions in Chapter 16 and diodes in
Chapter 17). Diodes are semiconductor devices that are the primary building block for more complex devices!
•
•
Diodes act likes a closed switch when they are properly “forward biased” (see question 1(e) above).
o
When the “switch” closes, you need to make sure there is a load (resistance) in the circuit path to limit the flow of
current within the continuous forward current specification or it will overheat/burn/explode.
o
A forward biased LED will emit light as some of the electrons drop out of the outer conducting valence band into
holes at a lower energy level (releasing a photon with a wavelength commensurate with the drop in electron
energy level).
o
When a diode (or LED) is properly forward biased, you can measure a small voltage drop across the diode (be
sure you know the typical voltage drops!!)
Diodes act likes an open switch when they are “reverse biased” (opposite of question 1(e) above).
o
Almost no current flows through the device (and no light emitted for LEDs). This one-way “current blocking”
feature can be very useful!
o
If the “reverse voltage” becomes too large (exceeds the “breakdown voltage), the diode “breaks down” and a
large current will flow “backwards” through the diode. With standard diodes, breakdown current may damage or
destroy the diode (exception: a Zener diode is specifically designed to work in the “breakdown mode”).
•
On an upcoming test you will need to know this basic information and to use it!!
•
There are hundreds of types of diodes. See page 823 for a summary of types and circuit symbols and page 810 to see
the packages. Look up data sheets for the 1N4148 small signal diode and for the 1N4004 rectifying diode (you have
or will use these in class) and compare some key characteristics with a green LED in the table below. Assume the
diodes were made by Fairchild Semiconductors (e.g., Google “Fairchild 1N4148 data sheet”)
Green LITEON
LED
n. Forward Voltage (if they specify a forward current with that
voltage, you should write x.xV @ y.yA)
o. Maximum forward current (a short current “spike” that may
occur as you turn your circuit on or off)
p. Continuous forward current (this is the typical largest average
current you would want to flow through the LED)
q. Maximum power dissipation
r. Reverse breakdown voltage
s. Reverse current
t. How can you identify the cathode on the package?
u. Draw the circuit symbol (also indicate where the cathode is)
v. Unit price (look up at Jameco, assume you buy 100)
Fairchild
1N4148
Fairchild
1N4004
3. Safe use of LED & Diodes in circuits: Make sure you know how to select the proper resistance to limit
the current flowing through an LED (or diode). Here’s the process:
a. Determine the forward voltage of the LED or diode using a data sheet (or use typical values discussed in class)
b.
Use the information above and Kirchoff’s voltage law to calculate how much voltage will drop across the resistive
load you plan to place in series with the diode/LED.
c.
Determine the continuous forward current using a data sheet (or use typical values discussed in class)
d.
Use answers to 3(b) and 3(c) with Ohm’s law to calculate the series resistor value.
Use the process above to solve these problems. Draw a circuit diagram and calculate the appropriate resistance value. Show
your work. Expect to see these questions on an upcoming quiz/test!
Light a red LED with a 9V battery
e.
Light two green LEDs in series with a
12V battery
Light a red and green LED in parallel
with a 6V battery
If you forget to include a limiting resistor in your circuit, the diode/LED with overheat/burn/explode. Perform this
experiment as a team: put on some safety goggle, plug a standard 5mm LED into a breadboard WITHOUT a resistor,
and use a variable power supply to increase the voltage until the LED fails. Record your observations. BE VERY
CAREFUL WHEN YOU PERFORM THIS EXPERIMENT—MAKE SURE YOUR NEIGHBORS AND
INSTRUCTORS HAVE SAFETY GOGGLES ON AND TELL THEM BEFORE YOU RUN THIS EXPERIMENT!
4. Transistors – read chapter 18 if you would like to learn more about transistors!
Transistors are semiconductor devices that can be used to amplify signals or as “solid state” switches. For example, the very
weak radio signals you received by your car radio are amplified perhaps 1,000,000X when you are blasting your radio! You
also saw in lab 4 how we used a 2N3904 bipolar junction transistor (BJT) as an electronic switch—a very tiny input current in
the base caused the flow of a much larger output current to flow through the emitter-collector (another form of amplification).
There are many types of transistors (see page 881 for a list and their symbols) that come in many different component packages
(shown on pages 872-874). When you design a circuit, the maximum current and voltage ratings, power dissipation, the gain,
and the switching speed are some of the important characteristics you should look at.
General Purpose/Small Signal Transistors
In the lab we have a variety of these low power transistors. Two common ones we use in the lab are the PN2222A and
2N3904 NPN General Purpose Bipolar Junction Transistors (BJT). By the way, the NPN tells you what type semiconductor
doping used to fabricate the device. PNP BJTs are also available (the 2N3906 PNP BJT is the “sister” to the 2N3904 NPN).
Essentially, PNP and NPN transistors operate with opposite base current direction.
a.
BJTs have three terminals: the base (B), collector (C), and emitter (E). Draw the circuit symbols for both NPN and
PNP BJTs and label B, C, and E on each diagram. These devices typically come in a TO-92 package. Draw the
package and label the pins B, C, and E.
NPN
b.
PNP
TO-92 Package
The first sentence on the Fairchild dat sheet for the PN2222A and 2N3904 list what two uses for these transistors?
__________________________________ and _________________________________________________
Key Data Sheet information
c. Maximum collector current (IC continuous). This is the key factor to look at if
you are using it as a switch—how much current do you need to run your load?
d. Maximum power dissipation
e. VBE Base-emitter saturation voltage (minimum)
f. Sum of Turn on delay time + Rise time
g. hfe (DC current Gain) (when IC = 10 mA)
h. hfe (DC current Gain) (when IC = 500 mA)
On your very expensive DMM you will notice that there is a place to plug in
BJTs to measure hfe. This is a quick way to figure out which leads are the E, B,
and C—the correct orientation will yield a much higher hfe than will the
backward configuration.
i.
Plug your PN2222A (or 2N3904) in and measure hfe
Record resultÆ
j.
Now plug the PN2222A “backwards” and measure hfe
Record resultÆ
k.
Unit price (look up in Jameco catalog or Jameco web site. Assume you
purchase 100 at a time.)
PN2222A
2N3904
Power Transistors – we commonly use field effect transistors for power transistors. For example, we have an n-channel IRF520 power MOSFET and its “sister”, the p-channel IRF-9620. FETs require a voltage to be applied from the Gate to the
Source terminals (VGS) to “switch on” the transistor.
l.
What does the acronym e-MOSFET stand for? _______________________________________________
m. Draw the circuit symbol for n-Channel e-MOSFET and p-Channel e-MOSFET, and label the Gate (G), Drain (D) and
source (S) terminals. Sketch the package for this device (it’s a TO-220) and label G, D, and S.
N-channel
P-Channel
TO-220 Package
Key Data Sheet information
IRF520
n. Maximum source to drain current (IDS continuous).
o. What voltage would you have to apply at the gate (VGS) to make IDS = 3A? (see figure 5)
p. What voltage would you have to apply at the gate (VGS) to make IDS = 7A? (see figure 5)
q. Maximum power dissipation
r. Maximum drain to source breakdown voltage (VDS)
s. Sum of Turn on delay time + Rise time
t. Unit price (look up in Jameco catalog or Jameco web site. Assume you purchase TEN at a time.)
u. According to the manufacturer, what are the recommended uses for the IRF520? Compare the specifications of the
2N3904, PN2222A, and IRF510. Do you understand why the IRF510 is called a power MOSFET?
5. 555 Timers – a classic example of a “black box” that performs a useful function!
The “555 Timer” is a well-known chip that has many practical uses for both beginners and experts. For example, the last
circuit in Lab 2 used the 555 timer in “astable mode” to turn an LED on and off in a very predictable (periodic) pattern.
Perhaps a blinking LED is not very useful, but with a bit of thought, you could think of many ways to use this controllable
output for much more useful purposes.
More important is the fact that all of these 555 applications are spelled out in the manufacturer’s data sheet for the chip (and if
you Google “555 timer” you will find hundreds of other resources, circuits, etc. for the 555 timer). Chips (integrated circuits or
“ICs”) have been developed to accomplish many useful tasks, including tasks you may find useful for your ATDF project.
The 555 is an “integrated circuit”—look at the schematic diagram on page 1 and you see that the IC contains many transistors
and resistors integrated into one package. However, as integrated circuits go, this is really a very simple IC with perhaps the
equivalent of a hundred discrete components. A personal computer microprocessor, for example, contains the equivalent of
tens of millions of discrete components onto a small (perhaps 10 mm x 10 mm) semiconductor substrate.
You’ll notice that the 555 data sheet contains a few pages of electrical specifications similar to the type of data provided the
discrete devices you looked up in parts 1 – 4 (the LEDs, diodes, and transistors). However, IC data sheets typically have many
more pages of information relating to the function of each pin, sample circuits, applications, etc. The 555 data sheet is 12
pages long. The data sheet for a microprocessor may be published in a number of volumes (books).
We have three types of 555 chips in our inventory (look at your chip to see which you have:__________)
o
LM555 (8 pin DIP) – this is the data sheet we handed out in class.
o
LMC555 (8 pin DIP) – this is a “CMOS” version of the LM555 – a different semiconductor fabrication process and
“architecture” is used. Functionally it is the same chip, but can you identify the key difference?
o
LM556 and LMC556 – these are “dual” 555 chips – they contain two copies of the 555 in one 14 pin dual-in-line
package (DIP). Why aren’t 16 pins needed (2 x 8 ) for the dual timer chip??
b.
Data sheet - device characteristics on first few pages…
What is the maximum current this device can “handle?” (source or sink)
“Source” means the chip (output = pin 3) provides current to an external circuit. “Sink”
means an external circuit connected to pin 3 supplies current to the chip. Note that the
direction of the current relates to standard current notation – current defined as positive
charge flow (opposite of what our book uses!).
What is the minimum source voltage (VS) that you may use?
c.
What is the maximum source voltage (VS) that you may use?
d.
What is the unit price? Look up at Jameco on web or in catalog in lab. Assume you
purchase 100 at a time.
a.
LM555CM
Look at list on
top of page 1!
LMC555
Look at list on
top of page 3!
e. Read the general description paragraph on page for the LMC555 (CMOS version). What are the primary benefits of using
the CMOS version compared to the standard 555 chip (TTL version)? Other than this difference the two chips have identical
functions and pinouts.
f. Read the first sentence of the general description paragraph on page for the LMC555 (CMOS version). What two functions
can the 555 timer perform?
________________________________________
and
_____________________________________