Cmos driving TTL through a diode

[Roff]

Some apps do not become affected by an inverted clock, especially when the clock pulse is narrow. If you read back in my post you'll see i mentioned that he would have to check that effect out to make sure an inverter doesnt bother the timing enough to cause a problem.
If one transistor does not work then two will anyway.

I do like the idea of an 'or' gate too though, or a 'nor' gate with a second section used as an inverter.

If for some reason a diode does have to be used, then i would recommend working with a Schottky diode with a lower forward voltage drop.

Since clock polarity is irrelevant, A NOR gate without an inverter would work.

 

[MrAl]

Hi Roff,

I just wanted to stay bipolar there (little pun) but i also did not want to assume an inverted clock would work because i do not know what he is using those two counters for and how wide the clock pulse is. I do like the idea of a 'nor' gate, or if need be a 'nor' gate with an extra section of the chip used as an inverter, whichever works best for his app.

 

[Roff]

Hi Roff,

I just wanted to stay bipolar there (little pun) but i also did not want to assume an inverted clock would work because i do not know what he is using those two counters for and how wide the clock pulse is. I do like the idea of a 'nor' gate, or if need be a 'nor' gate with an extra section of the chip used as an inverter, whichever works best for his app.

I sorta figgered the clock could not be very narrow if it is coming from a 4082.

 

[jerryd]

Roff,
I like the "OR gate" idea even though it's an extra package.
I'll try it as well as changing to cmos counters.

The clock is very narrow and it wouldn't matter if it
was inverted.

Got a lot of good info in this post and I get the message
that's it's not a good idea to mix technologies.

Thanks,
Jerryd