5532 channels parallel: how?

[Vigier]

Hi,

I have 2 simple questions. I have a lot of 5532A's, and I want to use them for a Linkwitz crossover, subsonic filter, phase shift etc.
I also have 5534's but they are not unity gain stable

The questions: can I use the channels of the 5532 in parallel:
just connect pin 1/7, 2/6 and 3/5 together and use it as a single opamp? Or do I need to use resistors in the outputs before I connect them together?

For decoupling: Sibatit 100n or MKS4-100n?

Thnx for your time!
Grtz, Joris

[AndrewT]

Hi,
you can use the 5534 at unity gain if you add the compensating capacitor as shown in the data sheet.
Do not parallel the 5532 channels.
The spare channel can be used as an input buffer or output buffer along with your filters. All filters are usually designed to be fed from a low impedance and feeding into a high impedance. The buffers can give you this and adjust the gain + or - (inverting)

[Vigier]

Hi Andrew,

thank you for your reply! I didn't know it was THAT easy to compensate for unity gain (you can also read this as that I didn't read the datasheet good enough)

Can you tell me anything about the choice of decoupling capacitors? I usually use MKS capacitors but since I have pretty much sibatits left, is that better or less than the MKS?

Kind regards,

Joris

[lineup]

Originally posted by AndrewT
Hi,
you can use the 5534 at unity gain if you add the compensating capacitor as shown in the data sheet.

I use the recommended 22pF between pin5 and pin8 of NE5534.
I use small ceramic disc caps as these are easy to find.

[AndrewT]

Hi,
the decoupling on the supply + & - pins should be ceramic to ground. You can also ceramic direct from + to -.
Decoupling slightly remote from the pins is usually electrolytic.

[AndrewT]

Hi,
I forgot to mention that a compensated unity gain 5534 is a lot slower than the published bandwidth figure.

If you need speed at unity gain then look for another pin compatible opamp that confirms good speed at your gain.

[Vigier]

Thnx guys!

I changed my PCB design for a cap between pin 5 and 8. And I took a better look at the datasheets. De compensating C makes it a lot slower indeed!
For the subwoofer filter (crossover, phase shift en subsonic) it won't be a problem, but for the filter for the front speakers that's not a good idea.
I'll look out for some better types (last project uses AD847JN), but since I need a lot of them, I'll have to get the money first

First: soms ceramic caps!

Grtz, Joris

[Eva]

Why do you want to paralell 5532?

[Vigier]

The amount of components around the opamp is too large for using both channels separate. And using the 2 channels in parallel makes it easier for the opamp --> less noise.

Grtz, Joris

[Eva]

You should improve your PCB layout, it's not so hard to use both channels independently, or even to use four channel op-amps in 14-pin DIP. On the other hand, you can't paralell opamps in such a way, each one should have its own feedback loop and the outputs should be joint with >50 ohm resistors to prevent excessive currents from flowing due to mismatching.