So based on all of your previous comments I've been able to fill in a few boxes.
Any other hints about identifying output types?
Thanks

Any chip that can output a high is not an open collector.

Look at source/sink ability, Open Collectors can only sink, totem pole and tri-state can source/sink, not always the same amount of current, but usually similar voltages.

Open Collector outputs, ,not in the 74xx family, are commonly used to switch the "low side"/ground connection of a higher voltage load (ULN2003).

The 7400 series with open collectors are used to "pull a bus line low" or being disconnected from it, and have relatively low current sink ability.

In general, totem pole or tri-state outnumber open collectors in most outputs.

 

Any chip that can output a high is not an open collector.

To pick a nit, a chip could be able to output an active high and still be open collector, just as long as it could not output and an active low. I know such chips have existed, but I don't know if any do any more. About the only thing I can think of where they might still be useful would be for multiplexing LED arrays.

 

Great information is provided about digital output and it is nice to read all posts.

 

Ahh... if only tinamishra were a human that bothered to ever read a single post.

Reminds me of the inane ads that you used to get anytime you did a search on Google. Off to the right you would get stuff like, "Save up to 60% on new types of digital output at Amazon"

 

I think you can safely assume that any three-state output is NOT also open collector..

A nice "pearl" - So an OE line requires more than just a simple "I'll enable a single transistor".
I usually see the OE line attached to a side of one of those "triangles" that stand for a buffer - but they never show you what's in the triangle

The common-cathode diodes they are talking about are clamping, or anti-kickback, diodes for use with inductive loads. It looks, to me, like the protection/parasitic diodes they show connected between the input (and the output) and the E pin are backwards. You want them to turn on if the input/output go more than 0.7V below the E voltage. As drawn, they would turn on once the input/output go more than 0.7V above the E voltage, which basically makes the circuit worthless.

This is a new piece of information for me. I've read about the anti-kickback diodes, and used them once in a PWM project I posted here - but never thought they would be built-in to a chip. So depending on power outputs, I might be able to connect a chip directly to an inductive source. Nice.

Any chip that can output a high is not an open collector.
This is the genious of the "open collector" concept. You can "change a state", but external circuitry determines how that state is handled. When I first saw that concept last year, it wasn't clear - now I use it all the time.


Look at source/sink ability, Open Collectors can only sink, totem pole and tri-state can source/sink, not always the same amount of current, but usually similar voltages.
Again, another "pearl".


Open Collector outputs, ,not in the 74xx family, are commonly used to switch the "low side"/ground connection of a higher voltage load (ULN2003).
Kind of like "pulling up/switchingon the ground"


The 7400 series with open collectors are used to "pull a bus line low" or being disconnected from it, and have relatively low current sink ability.

In general, totem pole or tri-state outnumber open collectors in most outputs.
Gotcha

So there a quite a few learning points here:
Active sourcing (totem=pushpull) Passive sourcing (open collector - NPN or PNP)
Open collector outputs are VERY flexible
Tri-state = active sourcing/output = totem/pushpull
If the datasheet doesn't specify the output type, look at the schematic.
If it's still unclear assume the type of output based on source/sink characteristics

The more I read this forum the more respect I have for what you guys go through in your EE training
and in your daily practice of wading throught the subtleties of any electronic circuit.
I cannot thank you enough for your time.

 

On a sidetrack, what kind of technology are you dealing with, SPQR?

 

On a sidetrack, what kind of technology are you dealing with, SPQR?

I'm a noobie - I've done electronics in one form or another since I was a kid, but it is not my profession, just a hobby.

Long-winded answer:
This series of posts was brought on by me trying to make a poor-man's frequency-counter/oscilloscope with a series of binary counters (just for fun). I didn't use another schematic, just made it up on my own.

I put the original together, and it worked "OK", but all of the LED's were flashing at different intensities, and nothing I did would change it very much. So I thought about a buffer to "standardize" all of the outputs (no matter what the power of the counter output, the buffer/driver will clean it up).

Which led me to buy a bunch of buffers drivers, which led me to want to learn more about them, thus this thread.

But this is a fantastic exercise for me because one of my future projects is a control system for hydroponics in my greenhouse. I'll need to control 120V pumps from a distance, and by choosing the right "driver/buffer" my problems will be minimized.

Short-winded answer:
1 - I need to choose "correct" buffers/drivers in the future
2 - I love to learn about almost anything

 

Thank you, very detailed. I find it amazing people volunteer to explain such information.

I have many questions for my current project, unfortunately I don't expect good responses or responses at all.

So the solution is to wait, think again, and choose one of the alternatives that look best.

Well my questions maybe don't have predefined answers, that is the reason.

I am forced for many of my projects pretty much to walk it all through without assistance.

Happy Growing.

 

I believe what takao meant was are you focusing on TTL chips (7400 series) or CMOS (4000 series)?

I presume from your previous posts that you are using 7400 TTL gates.

It is important to choose one and not mix the two. The two are very different in technology, specifications and performance.

 

I believe what takao meant was are you focusing on TTL chips (7400 series) or CMOS (4000 series)?

I presume from your previous posts that you are using 7400 TTL gates.

It is important to choose one and not mix the two. The two are very different in technology, specifications and performance.

I have heard 40xx CMOS and classic 74xx TTL are pretty "dead".

If any, 74HCxx is used or there are also families like LCX, ACT, more than 20.

Mixing 40xx and 74xx is not really a common issue.

Originally 40xx CMOS was intend to save power, but then Microcontrollers came up in the early 1980s.

The issue is also explained in the CMOS cookbook eventually.

Which I recommend even if it is dated, and many of the ICs no longer available.

I don't have a copy here and don't need it to rely on it, but would like to read it again some day.

 

Thank you, very detailed. I find it amazing people volunteer to explain such information.
I have many questions for my current project, unfortunately I don't expect good responses or responses at all.
So the solution is to wait, think again, and choose one of the alternatives that look best.
Well my questions maybe don't have predefined answers, that is the reason.
I am forced for many of my projects pretty much to walk it all through without assistance.
Happy Growing.

This forum is a fantastic resource. I try to limit my questions to one time per month - don't want to abuse generosity
But the people here are so knowledgeable, that when you read their answers you KNOW they know what they're talking about.

I believe what takao meant was are you focusing on TTL chips (7400 series) or CMOS (4000 series)?
I presume from your previous posts that you are using 7400 TTL gates.
It is important to choose one and not mix the two. The two are very different in technology, specifications and performance.

I'm pretty flexibile - I'll use anything that works!
Now I'm at the level where I can start to think about the difference between TTL and CMOS (lower volts 3.3, faster, higher impedence).
I "grew up" on TTL - I still have my "TTL Cookbook" from the 1970's when I built an S-100 Imsai.
But I'm starting to delve into the different type of chips and though they may have the same number 74xxYYYxxx -
their subtypes are different - so more study!

I have heard 40xx CMOS and classic 74xx TTL are pretty "dead".
If any, 74HCxx is used or there are also families like LCX, ACT, more than 20.
Mixing 40xx and 74xx is not really a common issue.
Originally 40xx CMOS was intend to save power, but then Microcontrollers came up in the early 1980s.
The issue is also explained in the CMOS cookbook eventually.
Which I recommend even if it is dated, and many of the ICs no longer available.
I don't have a copy here and don't need it to rely on it, but would like to read it again some day.

I remember I bought some 7400 NAND chips in the 1970's (I still have them!) and said "Wow, this is HIGH TECH!"
Things have come a long way - I just need to catch up!

 

I'm pretty flexibile - I'll use anything that works!
Now I'm at the level where I can start to think about the difference between TTL and CMOS (lower volts 3.3, faster, higher impedence).
I "grew up" on TTL - I still have my "TTL Cookbook" from the 1970's when I built an S-100 Imsai.
But I'm starting to delve into the different type of chips and though they may have the same number 74xxYYYxxx -
their subtypes are different - so more study!

Don't go mixing and matching devices from different families unless you know they are compatible -- there be demons in those waters if you don't.

The key on compability is the input/output specifications as far as high and low voltage limits for each state and current drive versus current requirements.

 

CMOS (4xxx) vs TTL (74xxx)

They both have their usefulness.
They are both good for general purpose experimentation.
If you already have a collection of 7400 ICs, ok to use them.
Same goes for a collection of 4000 ICs.

But don't mix the two in the same project unless you know what you are doing.

Generally:

7400 ICs require +5V supply, consume more current, can deliver more current, operate at higher speed.

4000 ICs operate over wider supply range, will work from 9V battery, consume very little current, high input impedance, very sensitive to static.

 

Another trait of the two: 7400 will tolerate floating inputs (not a good idea, but will usually work) and 4000 series will not.

 

74xx will see floating inputs as HIGH level, so you should keep that in mind.
Anyway leaving them floating is a bad habit, any EM interference can easily flip them, for example noise from other parts of a high-speed logic circuit or from switching high currents.

 

74xx will see floating inputs as HIGH level, so you should keep that in mind.
Anyway leaving them floating is a bad habit, any EM interference can easily flip them, for example noise from other parts of a high-speed logic circuit or from switching high currents.

https://www.youtube.com/watch?v=W-Wl1dhaMFc
This is what EMI from a CRT will do to a floating reset line (MCLR on a PIC).

I figured out that was the cause, setting the tristate correctly and the phenomena disappeared. It was kind of a "soft" bug that would appear when the battery was "flat".

 

This is a superb discussion - and probably worth enstantiating in some forum up in the "All About Circuits" book.
Some of it is mentioned in the TTL and CMOS sections, but not to this depth.

Again, a series of experts, with both academic and practical expertise, coming together with a stunning discussion - I thank you all.

I'm going to cogitate on this awhile, and will be building some one-chip demo buffer boards, on which I'll keep everyone updated.

 

This is a superb discussion - and probably worth enstantiating in some forum up in the "All About Circuits" book.
Some of it is mentioned in the TTL and CMOS sections, but not to this depth.

Again, a series of experts, with both academic and practical expertise, coming together with a stunning discussion - I thank you all.

I'm going to cogitate on this awhile, and will be building some one-chip demo buffer boards, on which I'll keep everyone updated.

Well, your wish is... well, someone's command, probably Tony's:
http://www.allaboutcircuits.com/vol_4/chpt_3/10.html

http://www.allaboutcircuits.com/vol_4/chpt_3/8.html

 

Well, your wish is... well, someone's command, probably Tony's:
http://www.allaboutcircuits.com/vol_4/chpt_3/10.html

http://www.allaboutcircuits.com/vol_4/chpt_3/8.html

Yes! those are the two pages I was referring to!