Combining seperate sync with a 7486

blackben123

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Hi All
I'm trying to combine seperate sync to make -Comp using a 7486. My wiring is this:

Pin 1 = H input
Pin 2 = V input
Pin 3 and 4 tied
Pin 5 tied to 14 (I'm starting with +Seperate)
Pin 6 = -Comp output
Pin 7 = Ground
Pin 14 = Vcc +5

I'm wondering if I need to ground any inputs for the remaining 2 unused gates-or can I just let them float?

Thanks Ben
 
Hi All
I'm trying to combine seperate sync to make -Comp using a 7486. My wiring is this:

Pin 1 = H input
Pin 2 = V input
Pin 3 and 4 tied
Pin 5 tied to 14 (I'm starting with +Seperate)
Pin 6 = -Comp output
Pin 7 = Ground
Pin 14 = Vcc +5

I'm wondering if I need to ground any inputs for the remaining 2 unused gates-or can I just let them float?

Thanks Ben

Good engineering practice is to always tie unused inputs - either high or low. During initial design and test, I usually tie these high with resistors so they can be used at a later date if needed. Tied to ground is fine as well and is usually easier.

Certain types of logic can be damaged if you leave the inputs floating - the 7486 doesn't fall into this category.

Also, on low power logic, the inputs can float in the never-never-land voltages (halfway between a logic high and logic low). The output can actually oscillate and become a noise source.

Ed
 
Good engineering practice is to always tie unused inputs - either high or low. During initial design and test, I usually tie these high with resistors so they can be used at a later date if needed. Tied to ground is fine as well and is usually easier.

Certain types of logic can be damaged if you leave the inputs floating - the 7486 doesn't fall into this category.

Also, on low power logic, the inputs can float in the never-never-land voltages (halfway between a logic high and logic low). The output can actually oscillate and become a noise source.

Ed

Thanks for the informative reply,Ed. Since I will never use the other 2 gates in this application; I'll ground the dead ones and be done with it, I assume you mean *all* 4?

I figured I'd ask, since I had to build this miniboard anyway...and the "ounce of protection..." thing-no big deal to do it right. Plus another excuse to tinker with it. I did mount a 180 ohm pot in the output line just to see if I can fine tune even more.

Overkill?? Waste of time?

Blackben
 
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