Original question:
LME49600: OPA1622 headphone amplifier design review / TINA-TI instability at low rail voltages
Tool/software:
Hi,
I am making a studio headphone amplifier product based on the AK4499EX DAC (as discussed in a linked post). I would like more output power than a single OPA1622 can provide (300mA current would be ideal, even at hot temperatures). I have come up with the following design. I would love any feedback!
Schematic PDF and TINA file/screenshot attached.
Hi Max,
I checked over your design in Tina. It appears to work fine and makes sense. If you are concerned at all about any spikes on the output due to plugging in and unplugging cables you may consider using TVS protection diodes on the board. This could even just be footprints for TVS protection in the event you find you need them.
TVS Diodes:
https://www.ti.com/interface/diodes/tvs-diodes/overview.html
One thing to note with the ballast resistors on the outputs is that there will be some associated offset voltage between amps and therefore not all the expected current will reach the load. Instead of 300 mA you may see somewhat less. The offset voltage between the amps will show up at the outputs of each and some current will be going into the some output(s). This may be insignificant for your design however. You will still see a significant increase in output drive capability with your method however.
An alternative idea is shown below
All in all I think your design looks good!
Best Regards,
Chris Featherstone
