Any reason to avoid contacting the NC pins (1, 5, 8) on a single DIP-8 op amp?

[Ben N]

I have been twisting myself into a pretzel to lay something out without touching them (first time with a single), but it suddenly occurs to me that one ought to be able to wire right through them, because they are (duh!) NC. Like, say, a feedback resistor between pins 2 & 6 - is there any reason I can't run that connection right through pin 1?

[EBK]

What specific chip are you talking about?

[ElectricDruid]

What specific chip are you talking about?

+1 agree. What chip is a big deal.

On many single op-amps, pins 1 and 5 aren't actually "NC" but rather they're "offset null" pins, so you don't want to be tying them to anything that has substantial voltages on it. So no, I'd say, don't wire feedback components through pins 1 or 5.

If you can guarantee from the datasheet for the specific chip that you're using that those pins are NC then, yes, you should be ok.

[Ben N]

TL071, NE5534, LM741.

[EBK]

In that case, steer clear of pins 1, 5, and 8.

They aren't NC pins at all, except for pin 8 on the tl071 and lm741.  Sometimes, manufacturers will give more detail about NC pins, such as when they can be used for additional thermal regulation, for example.   TI says "do not connect" in the tl071 datasheet.  I'd follow that.  If you need routing suggestions, show us what you've got so far.

[iainpunk]

TL071, NE5534, LM741.

all of those have functions attached to the pins you describe. you could, if you don't use that functionality, snip them off, but you can't use those pins as if they were NC.

i do have a UA741CP with 14 pins, of which 7 pins were actual NC pins

cheers

[Ben N]

Thanks, guys. In the meantime I managed the routing; although it is a bit ugly, it'll be fine. It's just a perf layout for a Tim Escobedo Octup Blender. Once it's confirmed I'll share it.

[iainpunk]

iirc the escobedo octup blender had 2 opamps, right?
are you using 2 singles instead of a double? if yes, why?

cheers

[Ben N]

It actually has three, two for the octaving and one to do the mixing. I could have drawn it for a pair of duals and just left one unused, but I've got a few singles sitting around doing nothing, so I drew it up for a dual + single.

[antonis]

BTW, sinking current from the "unused" compensation pin could result into interesting output amplitude results..

[anotherjim]

Sometimes NC pins are for factory testing and while it's often uncertain if it means "nothing is connected to the pin" or "Do not noway now-how never-ever connect to this pin"... it's probably best not to.

[Rob Strand]

You could cut the pins off then you don't have to worry about them all 

[Ben N]

You could cut the pins off then you don't have to worry about them all 

I did give that some thought, and if it ever turns out to be really necessary I suppose I'd do it.
But 👇

[composition4]

You could cut the pins off then you don't have to worry about them all 

I've done that one a couple of builds before, it's handy but it feels so dirty

[iainpunk]

i inherited a bunch of stock from a great uncle who passed in 2018, and about half of the UA741's only had 5 legs, the rest were snipped, to bad because they are the OG metal can package 741's

cheers

[duck_arse]

in my last and my current noise builds, I've traipsed across pin 8 on an LF351N and a CA741E with no problemms, got me where I wanted to go.

[Rob Strand]

i inherited a bunch of stock from a great uncle who passed in 2018, and about half of the UA741's only had 5 legs, the rest were snipped, to bad because they are the OG metal can package 741's

Yeah, cutting legs isn't good for re-use.     I have cut a few legs off as a kid but as a professional you try to do things the right way, even if it makes life more difficult  .

[ElectricDruid]

i inherited a bunch of stock from a great uncle who passed in 2018, and about half of the UA741's only had 5 legs, the rest were snipped, to bad because they are the OG metal can package 741's

Lol, sounds like he knew something we don't!

[Kevin Mitchell]

I've got a few singles sitting around doing nothing, so I drew it up for a dual + single.

Why not save them for where offset correction is needed?
Or hell, include the trim and see where it takes ya 

[iainpunk]

in my last and my current noise builds, I've traipsed across pin 8 on an LF351N and a CA741E with no problemms, got me where I wanted to go.

noise builds?
I'm intrigued, could you elaborate?

cheers