74HC74 pulse shaping

Maybe you can supply some additional info? Your question is a bit like asking "how long is a piece of string?"

There may be some ways of using a '74 to "square up" pulses, but without dividing by two or using the digital inputs by taking advantage of their analog properties which aren't well defined, I don't know of any.

Exactly what sort of distortion are you trying to "square up"? If it is the amplitude, I think you are using the wrong part. There are simple buffers with a Schmitt trigger input that will do that job.

The canonical method is to toss it out and use a 74HCT14.

If you're on Apollo 13 and will suffocate otherwise, it can be done. If you ground !set, then !q inverts !clr without latching. Use both sections in t he usual HC04 Schmitt connection.

Cheers

Phil Hobbs

LOL. That's impressively ugly. ;-)

--sp

You had me dreaming about pigs. (There's no verb form of "nightmare".) ;)

Cheers

Phil Hobbs

Thanks for the reply. I have a section of 74HC74 available unused that I'd like to use for this purpose without adding another IC. I was just curious if it was possible. Yes, it's essentially amplitude distortion, say you have a signal source that looks like what happens to a square wave when it's run through a differentiator and you want to square it up again.

I'm on Apollo 18 i.e. budget cuts

Well, if you're really desperate, you can set D high, dc couple the pulse into CP and AC couple it into !CLR. I wouldn't want to ride on that ship, though.

Make sure the !CLR pulse decays well before the next rising edge.

Cheers

Phil Hobbs

Do you have a non-inverting buffer? All that takes is two resistors and you have a Schmitt trigger. If the signal has a fast edge still, you don't even need the Schmitt trigger, just a buffer will do the job.

Oh, and be sure to knock off any undershoot with a Schottky diode to ground. Otherwise it's liable to misbehave even more.

Cheers

Phil Hobbs

Half-ass is better than no ass at all ?>:-} ...Jim Thompson

I have an op amp section available, but the problem is, it's like...not a fast op amp. LM324 variant probably. I don't think it will have the slew rate to generate the fast edges I want.

Setup violation on CLK, tsk tsk.

Not if the clear pulse decays soon enough, which was the point I was making.

Cheers

Phil Hobbs

Your recent posts are implying that you are doing "paste-on" "designing", taking a crap beginning and applying a patch, then discovering you need another patch, on-and-on...

Ever think of stopping and starting from scratch and doing it right? ...Jim Thompson

Your recent posts are implying that you are doing "paste-on" "designing", taking a crap beginning and applying a patch, then discovering you need another patch, on-and-on...

Ever think of stopping and starting from scratch and doing it right? ...Jim Thompson

Instead of Skylab, I wish the Apollo program had ended with something really outrageous, like the Manned Venus Flyby they had on the drawing board for years.

It likely could have been totally done even with mid 1970s technology, but would have required incredible endurance and huge brass balls on the part of everyone involved.

I'm mostly an audio guy. For the circuit I'm working on now that involves this sort of weird analog-digital hybrid thing, I'm just not terribly familiar with the techniques involved. If I see enough examples of "good" circuits I can probably figure how to adapt something to fit my needs.

In certain circumstances, yeah, I admit I sort of do "cut and paste" designing. I'm frankly just not good enough to start completely from scratch in certain areas that I'm not deeply familiar with.

I have no doubt it could have been done, but at what cost and for what benefit? How many lives do you think would have been lost?

In general I usually do, like, try to stay within the bounds of my own incompetence when doing things professionally