[kheldar]

does anyone know/have experience with stacking opamps? I have a basic CMOY type amp with lm6171 opamps, can I pop another opamp on top to increase the output current? and will i have to change the BW limiting cap, which is currently a 10pF in the feebackloop?

thanks guys

 

[jeffreyj]

You mean stack as in, literally solder one on top of the other?

Kinda, maybe, sorta but not really recommended is the answer. National only provides a simplified schematic of the LM6171's internals, so we can't tell whether an isolation resistor for the output is in circuit or not. I'd say that because of the high output current capability and slew rate of this op-amp it's not a good candidate for doubling-up.

But if you have a few to spare give it a try and report on the results.

 

[kheldar]

What is the likely end result if there isn't an output resistor in the chip itself? poor sound? or more likely to kill the chip?

 

[jeffreyj]

Well, it would be a stretch to say what would be the most likely end-result, but I'd put my money on high frequency oscillation (near the unity gain bandwidth of the device). Could be destructive, though not likely. Like I said, I wouldn't risk it especially since there really isn't any benefit to do such.

 

[kheldar]

oh well... time to rebuild my favorite amp then if the easy way wont work =)

 

[Lichoo]

http://headwize2.powerpill.org/proje...=opamp_prj.htm
see Figure 12a

Regards,

Piotrek

 

[kheldar]

I have seen that, and done it, im just trying to ad a bit more power to an old portable amp without making major modifications.. its beside the point now, im testing a new design on a prototype board now =)

pictures coming soon