Hi everyone I have been been reading AAC for a while now, this is the first time I have decided to post. I wanted to blog about 7400 series and how easy and fun it was to work with, if some of you don't mind can you give me your opinions and thoughts on the 7400 series ICs. I would appreciate pointers and tips the most. Also I blog about your tip in my blog I will give you credit for it, unless in your post your explicitly mention not too. Thank you all for your help. Kindly.


-Jigish Shukla

 

You may get some funny looks (virtually speaking). 7400 series - original TTL - is not only hard to find in most varieties, but is also considered power hungry and somewhat hard to use. I thought it was slick in 1969, but so much has been developed since.

Why are you interested in this logic family instead of the flavors of CMOS? CMOS has the old 4000 series in it, with the wide range of usable voltages, but the 74Hxx and so on families that are 5 volt CMOS with TTL pinouts.

 

Yes I realize that. I meant 7400 and 4000, where I work, the senior engineers use those two terms interchangeably.

 

Hello,

Take a look at these pages from the EDUCYPEDIA:
Arithmetic circuits
CMOS technology
Codes & decoders
Converters
Counters & registers
DAC/ADC types
Digital logic
Digital theory
Flip flops
FPGA Design
Memory
Number systems
Sigma Delta Conversion
Technology
Timers & oscillators
TTL technology

Each page has a lot of links on the different subjects.

Bertus

 

I cut my teeth learning TTL. I see several posts that are different than what I have learned and done. For example, open inputs on true TTL are assumed high. This is the only logic family this is true for. It has definately left its mark. Compare the BDC/LED decoders CMOS 4511 and the TTL 7447 pinout sometime, they are very similar.

If it comes to a choice between TTL and CMOS, I prefer CMOS. This is due to the wider voltage ranges for power supplies. The old LEDs dropped considerably less voltage than the new versions, so TTL is lagging a bit on that front too.

Having said all of that, I am very comfortable with TTL. Most cell phone chargers use +5V at 1A, so there are some quick and dirty power supplies all over the place for them.

 

Bill_Marsden: You are right, TTL has a lot of quirks one has to get familiar with. The guide I want to create is meant to be simplified and can be used by novices. Thus like I stated earlier I would prefer sticking with the 4000 series (at work seniors here use 7400 and 4000 interchangeably) .

Here are some thing I plan on including.

1.) Compensation Caps
2.) Fan out
3.) Reference Voltage
4.) A basic guide to sequential circuits for which I will refer AAC so, AAC also gets traffic.
5.) Pull up resistors
6.) Grounding

 

Get copies of both , "the TTL Cookbook" and "The CMOS Cookbook"

 

Bill_Marsden: You are right, TTL has a lot of quirks one has to get familiar with. The guide I want to create is meant to be simplified and can be used by novices. Thus like I stated earlier I would prefer sticking with the 4000 series (at work seniors here use 7400 and 4000 interchangeably) .

Here are some thing I plan on including.

1.) Compensation Caps
2.) Fan out
3.) Reference Voltage
4.) A basic guide to sequential circuits for which I will refer AAC so, AAC also gets traffic.
5.) Pull up resistors
6.) Grounding

Are you actually talking about 74HC00 and/or 74HCT00 series? Bipolar TTL (7400) is not strictly compatible with CD4000 series.

 

Are you actually talking about 74HC00 and/or 74HCT00 series? Bipolar TTL (7400) is not strictly compatible with CD4000 series.

Clearly, something is getting lost in translation here. When I started the conversation I had just assumed everyone referred to series of chips I am talking about the same way. I live in the States, I work for the government and the two senior engineers here (1 for 40 years (started very young) and the other for 25 years) both refer to the 74HC00/74HCT00 AND the CD4000 as the 7400 series chips. I am very clear on the fact that they are not referring to the TTL 7400. Now is this nomenclature something that is isolated to my work place? In a previous post someone stated I would get weird looks. I now understand why.

 

Some of us go back before 7400 TTL hit the shelves. In fact, before 800 series DTL. For clarity, use the family letters.

Why would someone lump 4000 CMOS in with TTL? Must be a workplace thing.

 

True 7400 series chips are probably not available in the marketplace except as old stock or for military repair, so referring to 74HC(T)00 as 7400 is understandable in the workplace where new design is being done. However, among hobbyists (who buy or have old stock), and old farts like me, 7400 series, being made in bipolar technology, is a completely different animal from the 7400HC(T) parts, which are CMOS.
74HC and CD4000 can be mixed in some applications, but the family power supply, drive capability, and speed characteristics are very different, and must be paid close attention to.

 

Yeah, when I think of 7400 series I think in terms of true TTL, not CMOS.

 

Nothing wrong with it, especially since they've come out with variants such as the HC, ACT etc.

The HC series is pin for pin 7400 stuff but it's CMOS internally.

 

Nothing wrong with it, especially since they've come out with variants such as the HC, ACT etc.

The HC series is pin for pin 7400 stuff but it's CMOS internally.

Yeah, but they don't always mix well.

 

Yeah, but they don't always mix well.

Not always, but most of the time they will, sometimes it's a hit and miss situation. If you use all HC or ACT types they are perfectly compatible, the trouble arises when you try and mix them in with some 4000 series ICs.

 

Not always, but most of the time they will, sometimes it's a hit and miss situation. If you use all HC or ACT types they are perfectly compatible, the trouble arises when you try and mix them in with some 4000 series ICs.

7400 is not perfectly compatible with 74HC00.

 

Nope, if you're going to be using one HC the rest should be too.