| Lovan |
I'm making a general headphone-amp using an opamp and stumbled upon the question if the outputresistor should be in the feedbackloop or outside?
/Niclas |
|
|
| AndrewT |
Hi,
are you referring to the resistor that sets the output impedance and also gives a resistive load to improve stability and a bit of short circuit/muting protection?
Then it goes outside the loop.
If the resistor is inside the loop then NFB tries to reduce it's effect to near zero. |
|
|
| Lovan |
Hi Andrew
Exactly my thoughts. Thanks for confirming them! :)
/Niclas |
|
|
| jcx |
you can have it both ways
resistive feeback around the series R reduces ouput impedance at low frequencies
C feedback from the chip output can dominate the feedback at high frequencies where the series R isolates the op amp output from destabilizing C load
more complicated with typical power chip amps that are not unity gain stable but still possible |
|
|
|
