I need a little more current than one of my OpAmps can provide, so am thinking about putting two of them in pin-to-pin parallel. They will both be in the same 8-pin DIP package, but I know they won't be perfectly matched. Anything in particular I should worry about or mandatory steps I should take to balance the load between the two units?

 

Have you considered using a follower (buffer) that can handle the current?

You are probably going to have to provide more information.

 

I need a little more current than one of my OpAmps can provide, so am thinking about putting two of them in pin-to-pin parallel. They will both be in the same 8-pin DIP package, but I know they won't be perfectly matched. Anything in particular I should worry about or mandatory steps I should take to balance the load between the two units?

Don't do it. Instead, buffer it, as already suggested. A schematic of that part of the circuit and information on how much current you need and what the voltage swing that you need is will help us help you better. Also, is the output signal changing quickly and swinging both positive and negative?

 

I need a little more current than one of my OpAmps can provide, so am thinking about putting two of them in pin-to-pin parallel. They will both be in the same 8-pin DIP package, but I know they won't be perfectly matched. Anything in particular I should worry about or mandatory steps I should take to balance the load between the two units?

How much current do you need?
Post the schematics of what you have now without two op amps in parallel.

Have a look at LM675 power op amp.

 

As noted, better to either use a current buffer, or a high-power op amp that can deliver the desired current.

Because of offsets, one op amp will likely try to provide all the current and the other little or none if you put their outputs in parallel.

 

Here's a couple of app notes from TI to say how to do it. A series resistor on the output is the important part, so that they both share current as equally as possible.
https://www.ti.com/lit/ab/sboa553a/...08085&ref_url=https%3A%2F%2Fwww.google.com%2F
https://www.ti.com/lit/ab/sboa352/s...24296&ref_url=https%3A%2F%2Fwww.google.com%2F

 

We need to know the details, voltage, current, bandwidth.

Here is one example of a buffer.

 

Thanks for the inputs and apologies for not offering more information. I would like about 40ma from the paralleled OpAmps which are driven by a very well-filtered PWM source, so bandwidth is not an issue. Paralleling the two OpAmps in the 8-pin DIP (junk box supply) would be a really simple solution, but I figured there might be issues with balancing the load between them per the datasheets IanO provided links to.

In the end, MrChips one transistor buffer clearly makes more sense (I'm only looking for positive output voltages anyway) and I'm darned if I know why it never occured to me. I guess I fell in love with the parallel idea

Thanks again.

 

As noted, better to either use a current buffer, or a high-power op amp that can deliver the desired current.

Because of offsets, one op amp will likely try to provide all the current and the other little or none if you put their outputs in parallel.

Or more likely even worse, one opamp will be putting out max or near max current while the other will be sinking max or near max current even if almost no net output current is needed.

 

Or more likely even worse, one opamp will be putting out max or near max current while the other will be sinking max or near max current even if almost no net output current is needed.

Assuming 1Ω output resistors and an offset of 5mV the maximum that could be delivered for a zero Volt output would be ±2.5mA

 

Assuming 1Ω output resistors and an offset of 5mV the maximum that could be delivered for a zero Volt output would be ±2.5mA

If that's an op amp input offset, then the current would depend upon that offset times the op amp circuit gain (which we do not know).

 

If that's an op amp input offset, then the current would depend upon that offset times the op amp circuit gain (which we do not know).

Assuming that TI's "leader follower" circuit is used, then the gain is unity.

 

Assuming that TI's "leader follower" circuit is used, then the gain is unity.

Yes, of course.

 

Yes, of course.

I think we've shown that it is better to use the "leader follower" option as it eliminates circulating currents caused by offsets.
I also wonder how likely it is that a pair of op-amps on the same chip would have the same offset voltage.

 

i guess such https://www.falstad.com/s.php?s=Czo8En configuration should be safe . . . relatively
! Update :
(the error will be less without equalizing output resistors - but at real life the inter-output currents can't be guessed then)
there was only one possible op amp model at dual config. NE5534 i had capable of 40mA RMS
and only LT318A at 3 in parallel had a similar error to dual NE5534
well ~ all virtual at LTspice

 

The transister buffer scheme makes much more sense, as I see it.

 

National Semiconductors had an AN explaining how to.

 

Does it need to source sink or both? That's important for designing a buffer