Datasheet

Application information TS488-TS489
24/32 Doc ID 11971 Rev 5
Note: In case F
CL
is kept the same for calculation, It must be taken in account that the
1st order high-pass filter on the input and the 1st order high-pass filter on the
output create a 2nd order high-pass filter in the audio signal path with an
attenuation 6 dB on F
CL
and a roll-off 40db ⁄ decade.
4.4 Higher cutoff frequency
In the high-frequency region, you can limit the bandwidth by adding a capacitor C
feed
in
parallel with R
feed
. It forms a low-pass filter with a -3 dB cutoff frequency F
CH
. Assuming that
F
CH
is highest frequency to be amplified (with a 3 dB attenuation), the maximum value of
C
feed
is:
Figure 79. Lower cutoff frequency vs.
input capacitor
Figure 80. Lower cutoff frequency vs.
output capacitor
1 10 100 1000
10
100
1k
10k
Rin=50k Ω
Rin=100k Ω
Rin=20k Ω
Lower Cut-off frequency (Hz)
Cin (nF)
Rin=10k Ω
0.1 1 10 100 1000
10
100
1k
10k
R
L
=32 Ω
R
L
=600 Ω
R
L
=16 Ω
Lower Cut-off frequency (Hz)
Cout ( μ F)
Figure 81. Higher cutoff frequency vs. feedback capacitor
F
CH
1
2π R
feed
C
feed
⋅⋅
---------------------------------------------=
0.01 0.1 1 10 100
100
1k
10k
100k
Rfeed=40kΩ
Rfeed=80kΩ
Rfeed=20kΩ
Higher Cut-off Frequency (kHz)
Cfeed (μF)
Rfeed=10kΩ