I'm building an LM3886 chipamp, non-inverting.
It has a 10k resistor (Rin) from the non-inverting input to ground.
This will be fed by a first-order RC low-pass filter to keep out the RF garbage. I'm looking at a 2 MHz corner frequency.
As Rseries gets large, and C gets small, then the loading of Rin will have an effect on the RF filter, which makes analysis more complicated, but for this to be a concern, Rseries will have to be so large as to cause undesirable attenuation in the audio band.
As a rough approximation, the C//Rin combination alone will determine the phase between the input current and input voltage at 20 kHz.
For a given corner frequency, as Rseries decreases, C must increase, which increases the phase angle between the input current and voltage.
Is a line-in generally expected to be resistive?
What amount of phase angle is considered normal at 20 kHz? When can I expect problems?
At 20 kHz:
82 pF // 10k = 6 deg
100 pF // 10k = 7 deg
150 pF // 10k = 11 deg
It has a 10k resistor (Rin) from the non-inverting input to ground.
This will be fed by a first-order RC low-pass filter to keep out the RF garbage. I'm looking at a 2 MHz corner frequency.
As Rseries gets large, and C gets small, then the loading of Rin will have an effect on the RF filter, which makes analysis more complicated, but for this to be a concern, Rseries will have to be so large as to cause undesirable attenuation in the audio band.
As a rough approximation, the C//Rin combination alone will determine the phase between the input current and input voltage at 20 kHz.
For a given corner frequency, as Rseries decreases, C must increase, which increases the phase angle between the input current and voltage.
Is a line-in generally expected to be resistive?
What amount of phase angle is considered normal at 20 kHz? When can I expect problems?
At 20 kHz:
82 pF // 10k = 6 deg
100 pF // 10k = 7 deg
150 pF // 10k = 11 deg