# Newbie. Need help, fast! Have no idea on any of these...

Discussion in 'Homework Help' started by intactusageof, Aug 4, 2010.

1. ### intactusageof Thread Starter New Member

Aug 4, 2010
1
0
I have no idea on how to answer all of these questions! I'm a student taking a computer science course. I'm got my ways when it comes to programming but I'm got this engineering subject up on my back! As of now, I think I'm failing this subject since I've got little knowledge when it comes to this. (K-map, nand gates, combinational circuits and stuff..)

I've got a lab report that I'm almost finished with. All I need to do is find answers to the following questions. (I've finished writing the objectives, introductory information, materials/equipment, the procedures of the lab experiments and its data results and its analysis. My prof gave me these guide questions that seemed unrelated to the lab experiments) But, I'm shocked to see that my prof. haven't discussed them!

Anyway these are the questions: (sorry if I just copied of my lab report...)

1: Derive the Karnaugh-map for the 7447 decoder (without the LT, BI/RBO, nor RBI inputs) and give the expressions using NAND gates. Obtain the internal equivalent circuit for the 7447.

2: Enumerate the unique features of each BCD to 7-segment display decoder/driver.

3: Show how you would connect a 3-digit display such that any leading zeroes will be suppressed.

4: What is intensity modulation? What is the advantage of this method over using the potentiometer to adjust the brightness of the LED?

5: Is it possible to use seven individual resistors for better series limiting? How would you compute for the resistance?

6: Show how two 74251 8-to-1 line multiplexers may be connected to implement a 16-to-1 MUX.

7: What are the advantages and disadvantages of the MUX and the decoder methods over conventional methods?

8: What are the advantages and disadvantages of the MUX and the decoder methods over one another?

9: Describe how a combinational circuit may be implemented using decoders given the minterm list form of two functions. (I really don't know what the question meant by "given the minterm list form of two functions" I don't know if it meant like any two functions, dunno)

If someone who like to help, I gave my deepest thanks to you!

2. ### Papabravo Expert

Feb 24, 2006
10,340
1,850
So what do you have so far??

3. ### JDT Well-Known Member

Feb 12, 2009
658
85
What you need is a copy of the old Texas Instruments 74 series Data Book. Used to be on every electronics engineers bookshelf 30 years ago!

Failing that, go to:-
http://www.datasheets.org.uk/
and search for SN7447A and SN74251. Have a look at the data sheets. Should give you some clues.

How to connect two 8-1 multiplexers to make a 16-1 has been answered recently in this forum (by me).

4. ### Audioguru New Member

Dec 20, 2007
9,411
896
My TTL data book wore out 40 years ago. Nobody used 74xx TTL ICs since so I didn't replace it, I got a Cmos cook book instead.
I think the teacher's questions are stuck in the '70s.

5. ### Wendy Moderator

Mar 24, 2008
20,772
2,540
I still see a lot of TTL logic out there. BJTs are dying hard.