Hi Everyone.
I see in the TPA301D Amp spec sheet that a 5pf capacitor is recommended if RF > 50K. A value of 5pf is shown. If RF is less than 50K a capacitor is not needed I believe.
I've been reviewing a circuit designed by a predecessor who had placed a 100pf capacitor in place of the 5pf. It may bring the potential low pass cutoff frequency below 20KHz in to an audio range which I believe is not the intent of the capacitor. Can someone verify this for me? Is the capacitor either not populated or 5pf? Or is there ever a more appropriate value? My coworkers think this is to stop high frequency noise from the speaker but I don't think that is the intent of that capacitor. Are there any side-effects of having too large a value (if it is too large).
Thanks!
Spec Sheet note
"For high-performance applications, metal film resistors are recommended because they tend to have lower noise levels than carbon resistors. For values of RF above 50 kΩ, the amplifier tends to become unstable due to a pole formed from RF and the inherent input capacitance of the MOS input structure. For this reason, a small compensation capacitor, CF, of approximately 5 pF should be placed in parallel with RF when RF is greater than 50 kΩ. This, in effect, creates a low-pass filter network with the cutoff frequency defined in Equation 7."
