I'm amazed that experts would need a circuit of a buffer.

You completely missed the point.

Can someone with more experience of using 4000 series ic's explain what is going on with a very simple circuit.
...
I do not have a lot of experience with working with logic I.c's.

Given your explicit statements about the circuit and yourself, I wanted to see the schematic so I could see if you had made a mistake. An accurate and complete all-text description of a circuit schematic is not a simple thing for an experienced professional, let alone for someone with "not a lot of experience". The same applies to your evaluation of the circuit as "very simple". Give the way *you* set up the question, I don't think that asking for a schematic ***in an electronic circuits forum*** was unreasonable.

We didn't need a circuit of a buffer, we needed to see *your* circuit of a buffer.

ak

 

You completely missed the point.

Given your explicit statements about the circuit and yourself, I wanted to see the schematic so I could see if you had made a mistake. An accurate and complete all-text description of a circuit schematic is not a simple thing for an experienced professional, let alone for someone with "not a lot of experience". The same applies to your evaluation of the circuit as "very simple". Give the way *you* set up the question, I don't think that asking for a schematic ***in an electronic circuits forum*** was unreasonable.

We didn't need a circuit of a buffer, we needed to see *your* circuit of a buffer.

ak

Ok

 

At this point, I see no reason to suspect latchup, though it is possible. Triggering (and that is an appropriate word) latchup usually requires exceeding voltage and current limits. For CMOS a likely culprit is current injection at the input due to exceeding the allowable input voltage.

We are back to a lack of a schematic and confusion from the statement at #36. Failure to meet input logic levels is very much in conflict with issues with the protection diodes. You can't make the protection diodes conduct unless the input voltage exceeds not only the required logic levels but also the power supply rails ("exceed" meaning more negative than logic 0 and "ground" or more positive than 1 and Vdd).

What was the voltage swing of the input signal when the supply for the buffer was raised to 7.5 volts or greater?
Did operation return to normal if the supply was then lowered again without actually cycling the power?

Because the complement outputs are unbuffered (true outputs are buffered), the large, high-current (all relative, of course) FETs can cause substantial shoot-through current if the input voltage is within the range that allows both FETs to be partially enhanced. Even with normally sized output FETs in 4000 series, this current can reach into the 15+ mA range. The 4041 output source/sink spec is 4 times higher than a normal 4000 output, so shoot-through of several tens of milliamps per output is not unlikely. Bad input logic levels could therefore cause high power dissipation without latchup. The behavior originally described could be accounted for with a 5 volt input signal to the 4041 when the latter's power supply was raised to something in the 7 volt range.

 

I don't see any miss quote.

If any member is requesting assistance in anything electrical and electronics on AAC forums then it is expected that that member should provide circuit schematics, links to applicable references and datasheets and all pertinent information. It is not acceptable that others should have to go and look things up by themselves.

When a solution has been discovered, it is simple courtesy to reveal and describe to the membership at large what was the solution.

I totally agree on the sharing of information for the benefit of all and also see the point Reckless is making about circuits and people asking for them. The blanket rule that a post must always include a circuit is not always appropriate or necessary and there are those on this and other forums who seem to use the absence of a circuit as an excuse to admonish the OP for the apparent oversight when they really don't appear to actually have anything to contribute anyway. In my opinion, it is they and not the OP who have started with the narky attitude but only the OP has been on the receiving end of a moderator reprimand. It does seem a little unfair especially as the persons complaining about the lack of data might have just moved on instead of posting inflammatory remarks. I had no trouble helping this OP without a circuit or a data sheet. Perhaps the the ones complaining are actually complaining that they have nothing to contribute and that bothers them so they lash out.

This is how it looks to me anyway. Reckless is not the one that started with the narky attitude as far as I can see, and while it is a regrettable thing, incorrect or incomplete attribution of blame (and in a public forum) is definitely worse.

 

The blanket rule that a post must always include a circuit is not always appropriate or necessary and there are those on this and other forums who seem to use the absence of a circuit as an excuse to admonish the OP for the apparent oversight when they really don't appear to actually have anything to contribute anyway.

It is never inappropriate to post a schematic when talking about circuits, no matter how simple. In this case, the lack of a schematic prompted a number of clarifying questions. A schematic would have communicated the circuit connections more definitively.

A number of members ask for schematics to avoid problems with wordy, possibly inaccurate or confusing descriptions of connections. I'm one of them. I'd rather work on solving problems instead of playing a game of 20 questions trying to pry relevant details from the poster.

When the OP started talking about input protection diodes becoming forward biased, it became apparent that his description of how things were connected was missing some key information. Without stating that multiple supply voltages were involved, raising the supply voltage would apply to all components. If that were the case, no input protection diodes could become forward biased and result in devices becoming SCRs.

 

It is never inappropriate to post a schematic when talking about circuits, no matter how simple. In this case, the lack of a schematic prompted a number of clarifying questions. A schematic would have communicated the circuit connections more definitively.

A number of members ask for schematics to avoid problems with wordy, possibly inaccurate or confusing descriptions of connections. I'm one of them. I'd rather work on solving problems instead of playing a game of 20 questions trying to pry relevant details from the poster.

When the OP started talking about input protection diodes becoming forward biased, it became apparent that his description of how things were connected was missing some key information. Without stating that multiple supply voltages were involved, raising the supply voltage would apply to all components. If that were the case, no input protection diodes could become forward biased and result in devices becoming SCRs.

I don't understand why anybody would bother to reply to a post that they feel has insufficient information. I also don't understand why anybody would respond in a nasty tone to a post that does not have, in the their opinion, sufficient information. If the OP does not ask 'properly' they hurt only themselves, so why should others reply in such hurt tones? Where is the offence? It is not rational to be narky because of a perceived error by someone else and that has no effect on anybody but them.

 

My original post was only meant as a "quickie" in as much, I was hoping that some of those with great experience of working with the 4000 series cmos, would have identified the condition as something common that could occur. Yes, I could have drawn out a full circuit, but I wrongly assumed that my explanation was reasonably sufficient for a quick answer. Maybe Pedant Engineer and I have a greater ability to visualise the circuit from the description than others, and due to that, I failed to satisfy the others parameters and framework for them to help.
What I took some exception to, was the manner in which I felt lambasted for not doing so.
I can fully appreciate that what to some appeared a vague description, would not enable them to help.
Maybe my background as a development engineer where I had to almost second guess what designers had in mind when they presented my team and I with scribbled drawings and only outline requirements for a given project, where we were then expected, and usually succeeded in producing a working model.
Maybe it is due to the different methods of education and childhood activities that are used nowadays. I grew up just after WW11 in a desperately weakened country where "make do and mend" was the norm. Meccano being the only toy I had, I soon learned how to integrate ideas from one construction into another, All my electronics was learned primarily from reading and from cannibalising scrap radios and ex WD equipment. Later I went on to further education to gain my degree, but before then and since, electronics has remained a lifetime hobby, career, and now retired, a hobby again.
My simple philosophy with electronics is........"I know what I know, and what I don't, I'm never too proud to ask those who do"
(But I don't lecture in a schoolmaster fashion when someone asks me a question)

 

Maybe Pedant Engineer and I have a greater ability to visualise the circuit from the description than others,

There is no ability required for you. You don't have to visualize anything. It's your circuit. You've seen (drawn?) the schematic and have been wrestling with debugging for hours/days/weeks, so you are intimately familiar with it. No one else on planet earth, now matter how in the know, has your knowledge base. Recognizing this is a critical component of a good question.

ak

 

I don't understand why anybody would bother to reply to a post that they feel has insufficient information. I also don't understand why anybody would respond in a nasty tone to a post that does not have, in the their opinion, sufficient information.

Before you try to judge my motivation, read a few thousand of my posts.

 

I don't understand why anybody would bother to reply to a post that they feel has insufficient information.

To help them learn.

ak

 

If the OP does not ask 'properly' they hurt only themselves, so why should others reply in such hurt tones? Where is the offence?

While some overreact, there is a legitimate gripe. This is an electronic circuits forum - its right there in the title. To try to discuss a circuit without a schematic is not naive or uninformed, it is unaware. Depending on circumstances, it also can be lazy. It disrespects the time others volunteer to help those less experienced. Remember, this is a question-and-answer dynamic. By definition, those with less experience are asking for free help from those with more. Telling a total stranger (that you are asking for free help) that they are not "in the know" or "can't visualize" because they cannot magically divine what is in the TS head isn't just rude, it's stupid.

ak

 

In reply to Analogue kids remarks, once again you choose to quote me out of context (reference my post 47 and yours in post 48) to skew the meaning of my words to suit your agenda. As you seem to be so adept at this, maybe you should think about a career in politics.
It also seems you are wrong by assuming no one else on the planet would understand my description. At least one other has.
As for being stupid, I think maybe the boot is on the other foot.
If you are unable to "magically"? divine something from a description, by which you mean visualise. then don't comment.

Had the question been, "I have a mains voltage light bulb wired correctly to a fused plug. When connected to a known working wall socket the bulb does not light" You would by your reasoning, still need a circuit diagram before you can think of any possible reasons as to why it does not work.
As for being rude, my post 47 was intended to show the original motivation for my question being as it was, and should have served to explain where I see my shortcoming in my first post. But no, you choose to ignore the explanation and continue with your nit picking agenda just to be nasty. Well I'm sure you are getting whatever satisfaction you require from doing so, but now you are losing some respect by continuing in this fashion.

 

Normally I would suggest checking the fuse and/or changing the bulb, but for you I would question "wired correctly".

ak

 

It is never inappropriate to post a schematic when talking about circuits, no matter how simple. In this case, the lack of a schematic prompted a number of clarifying questions. A schematic would have communicated the circuit connections more definitively.

A number of members ask for schematics to avoid problems with wordy, possibly inaccurate or confusing descriptions of connections. I'm one of them. I'd rather work on solving problems instead of playing a game of 20 questions trying to pry relevant details from the poster.

When the OP started talking about input protection diodes becoming forward biased, it became apparent that his description of how things were connected was missing some key information. Without stating that multiple supply voltages were involved, raising the supply voltage would apply to all components. If that were the case, no input protection diodes could become forward biased and result in devices becoming SCRs.

Even if it were true that it is never inappropriate, that does not mean it is always necessary. If the OP appears to know his stuff, is it not fair to assume they have the circuit correctly done? It seems somewhat arrogant to me to insist on a circuit from a poster who may well be far more advanced and technically savvy than me, and to do so in, lets face it, condescending tones as it is so often done is the height of rudeness. Better to simply ignore the post. You are not obliged to reply in the first place, so check your haughtiness and just move on is my view of these things.

And that is what I am going to do now with this thread. Too silly for words.

 

There is no ability required for you. You don't have to visualize anything. It's your circuit. You've seen (drawn?) the schematic and have been wrestling with debugging for hours/days/weeks, so you are intimately familiar with it. No one else on planet earth, now matter how in the know, has your knowledge base. Recognizing this is a critical component of a good question.

ak

Seriously, several of you are abusing Reckless because you cannot help him. Your good samaritan instincts are way too over developed. One of you has even boasted about thrashing out the need for circuits thousands of times! There is an expression that says something about repeating the same mistake and expecting a different result is not an indication of smarts. Perhaps you all like bashing your heads against brick walls because it feels so good when you stop.

Either way, what you are doing is abuse.

 

If it is a TTL buffer, why is it running on 7.5 V?

Actually, those in the know know that *nothing* in electronics is self-explanatory, ever. Ever. E.V.E.R.
Of the millions of integrated circuit types and variations in use, I keep the pinouts and internal schematics of only a few hundred thousand in my head. Sorry I can't be more help. Maybe someday I'll be in the know.

ak

Pretty sure a CD4xxx isn't TTL - the "U" in the suffix means unbuffered, which probably supports the widest supply voltage range. No idea what the remaining suffix letters mean.

There are TTL versions of most 4xxx types - but the most popular ones are prefixed by "74".

 

There are TTL versions of most 4xxx types -

Without being *too* pedantic, it's the other way around. CMOS was developed by RCA in response to TI's TTL parts, as a way to get a share of the burgeoning logic market without paying for all of those messy patents. I forget their names, but I met the two guys who took the Fairchild paper and ran with it way back when.

ak

 

Without being *too* pedantic, it's the other way around. CMOS was developed by RCA in response to TI's TTL parts, as a way to get a share of the burgeoning logic market without paying for all of those messy patents. I forget their names, but I met the two guys who took the Fairchild paper and ran with it way back when.

ak

TTL took over from DTL, and that took over from RTL - the evolution of CMOS was pretty much a new direction. There are CMOS logic elements absorbed into the TTL format - but they don't have CD4xxx part numbers.

 

While some overreact, there is a legitimate gripe. This is an electronic circuits forum - its right there in the title. To try to discuss a circuit without a schematic is not naive or uninformed, it is unaware. Depending on circumstances, it also can be lazy. It disrespects the time others volunteer to help those less experienced. Remember, this is a question-and-answer dynamic. By definition, those with less experience are asking for free help from those with more. Telling a total stranger (that you are asking for free help) that they are not "in the know" or "can't visualize" because they cannot magically divine what is in the TS head isn't just rude, it's stupid.

ak

It might be stupid and rude if the OP had not provided all the details he did. There was adequate information supplied to answer the question. It is not the fault of the OP if you have nothing relevant to offer. What word would you use to describe the behaviour of a person responding to a post that they cannot respond to with anything relevant? And then their behaviour when their reply is rebuked? They were your words AK, you just got the attribution wrong.

 

Time to knock it off.

AAC is a cooperative electronics site for sharing ideas and helping each other, not for name calling and bickering.