TL074 quad op amp?

[jmusser]

I believe it was R.G. who mentioned one time that he wasn't really crazy about using quad op amps in his circuits, and preferred to use two duals instead. The Stompbox Cookbook has several projects that uses either the TL074 or the MC33174 (which I've never heard of). Would the reasoning be because they are not as good noise wise as say two TL072s, or is it just is it just due to the congestion of peripheral supporting components, for a quad layout? Also, if I am to use a quad, is there a better choice since the writing of this book, then the two quads mentioned? Using duals, is always an option though.

[petemoore]

I read about  quads, after trying one project with a quad. It had noise problems mostly. Could have been partly at least caused by my not so slickly laid out perfboard build, I decided two duals will work.

[Paul Perry (Frostwave)]

I think it is only a layout problem.
What you save spacewise using  quad, in my experience is usually lost because of the reduction in freedom of layout.
plus, sometimes you might want to decouple the power supply to an LFO... no chance if that op amp is sharing a power pin with three others!!

[Mark Hammer]

Paul is bang on.

There are certainly plenty of cases where a quad can save you tons of space and headaches, but layout is definitely easier much of the time with dual op-amps.

[sean k]

I like TLO74's

this is a paralooper and the other ones a Bazz Fuzz (for hooking up to a 4 pole rotary) and the one question I have about this quad opamp is...is it a tl oh 74 or a tl zero 74?

[grs149]

I agree that there are no real performance issues in using quad op amps. I have used TL084s with no problems, other than circuit board congestion. Save them for applications where you need a lot of identical op amp "building blocks" that don't involve too many external resistors/capacitors. The gyrator circuits for a graphic equalizer would be a good example of this.

[R.G.]

There are no performance issues between duals and quads of the same family that I know of.

I prefer duals because they consistently give me the opportunity to make more compact, logically laid out PCBs than quads.

I thought about this a lot and figured out why. Unless you're using a lot of opamps as followers with output shorted to inverting input, one opamp usually has more resistors and caps connected to it than it has pins. That is, with only a (+),  (-), and an output, you usually have more than 3 parts connected. So you have to funnel down more than 3 parts to only 3 pins. That means that the parts are wider than the 0.2" that 3 pins take, often 0.4" or 0.5". If you are forced to put two of these setups side by side like one side of a dual, then you overflow the number of pins on the part by quite a big and have to back away from the IC package to get all the other parts on the board and funneled down to the opamp pins.

In addition, the outputs of a dual are on the same end of the package. On a quad, they are on the corners. Layouts have a preferred direction of signal flow. On a quad, you're certain that half the package goes the wrong way to match with the signal flow. Using two duals lets them all go the preferred direction, and it only costs you two more power pins. A bargain!

[Paul Perry (Frostwave)]

the one question I have about this quad opamp is...is it a tl oh 74 or a tl zero 74?

Zero, pronounced 'oh'.... which reminds me... what happened to Zero the Hero??

[nelson]

He is still around.

[jmusser]

Thanks RG. For some reason, I hadn't been notified that there was still activity on this post. I knew I'd read that you had a preference for some reason for duals, but just couldn't remember why. I figured it was layout oriented.